Category: Sourcing Guides

A caterer loads twenty bags with chilled sandwiches at six in the morning. By eleven the liners are grey with meltwater, two bags have damp patches on the outside, and the client is asking for thicker foam. The foam was never the problem. The liner seams had been sewn.

An insulated cooler bag is the most technical thing in a non-woven range. It is a laminate assembly with three jobs that pull against each other: reflect radiant heat, resist conduction, and stop air moving. Almost every complaint in the field traces to the third one, and the third one is decided by seams and closures rather than by millimetres of foam.

Three heat paths, one common misdiagnosis

Heat reaches your chilled goods by radiation, by conduction and by air exchange. Each has its own countermeasure inside the wall of the bag.

Radiation is handled by the reflective inner face. A bright aluminium surface turns back most of the infra-red arriving from a warm van roof or a sunlit pavement, which is why the liner is silver rather than white.

Conduction is handled by the foam. What insulates is not the plastic but the still air trapped in closed cells; the polymer is only the scaffold holding that air in place. This is why a dense, heavy foam can perform worse than a lighter one of the same thickness.

Air exchange is handled by nothing at all in most bags, and it is usually the dominant loss. Warm outside air entering through a zip line, a needle hole or a gap at a folded corner does not have to conduct through anything. It arrives already warm and carries humidity with it. Doubling the foam while leaving a leaking closure buys you very little, and buyers who go back to the factory asking for 8 mm instead of 4 mm often report no improvement, correctly.

The liner: metallised film or true foil

Both look like foil in a photograph. They are not the same material and the distinction shows up after a few weeks of use.

Metallised film, normally VMPET, is polyester film with aluminium vapour-deposited on it in a vacuum chamber. The metal layer is a few tens of nanometres, thinner than a wavelength of visible light. It is bright, cheap, flexible, and it survives folding well. It also scuffs: drag a crate corner across it and the metal comes off in streaks, taking the reflectivity with it. As a vapour barrier it is good rather than absolute, because pinholes in such a thin deposit are unavoidable.

True aluminium foil is rolled metal, typically 6.5 to 9 micrometres, laminated between a protective outer film and an inner sealing skin. It reflects more, blocks water vapour outright, and does not lose its metal to abrasion. The trade-off is brittleness. Aluminium work-hardens at a sharp fold, so a repeatedly creased corner develops microcracks and then a wet patch. Where a pattern puts a hard fold in the base corners, foil wants a radius or a gusset rather than a knife crease.

The full laminate matters as much as the metal. A typical build is an outer PET or nylon layer for puncture resistance, the metal layer, a foam or PE core, and an inner polyethylene skin that lets the seams be welded shut. Ask what each layer is. A liner quoted only as “aluminium foil” tells you nothing about the three layers doing the mechanical work.

One test costs nothing at the sample stage. Peel a corner of the liner laminate by hand. If the layers separate cleanly with light pressure, the bond is weak and the liner will delaminate at the folds in transit, whatever the specification sheet says.

Foam: type before thickness

Most enquiries arrive specifying thickness alone. Foam type changes the answer more.

EPE, expanded polyethylene, is the standard: the familiar white pearl-cotton foam, cheap, light, easy to laminate, available from about 2 mm upward. Its cells are relatively coarse and the sheet compresses permanently under sustained load, so an EPE wall that has been packed tight and stacked for a month is thinner than it started.

XPE, cross-linked polyethylene foam, has finer and more uniform closed cells. It insulates better per millimetre, recovers its thickness after compression, and takes welding heat more predictably. It costs more and is the sensible choice where the bag is reused daily or where wall thickness has to stay slim for the finished bag to fold flat.

EVA appears where structure is wanted as well as insulation, in moulded lunch bags and semi-rigid cases. It is heavier and stiffer, and it is a construction decision rather than an insulation upgrade.

On thickness, the returns fall away fast. Going from 2 mm to 4 mm makes an obvious difference. Going from 4 mm to 8 mm makes a smaller one, and by then the wall is bulky enough to change how the bag folds, ships and stores. Past roughly 5 mm the sealing quality of your closure almost always limits performance before the foam does.

Seams: a welded liner inside a sewn shell

This is where the caterer’s bags failed, and where price differences between two visually identical quotations usually live.

A sewing needle makes a hole through every layer it passes. In a shell that hole is harmless. In a liner holding melted ice it is a wick, and binding tape over the seam slows the leak rather than stopping it. Meltwater then travels into the foam, where it stays, and a bag with wet foam has lost most of its insulation value and will smell within a week.

The proper construction is two separate assemblies. The liner is cut and welded into a sealed bladder, heat or high-frequency welding fusing the polyethylene inner skins to each other so the seam is a continuous joint with no perforation. The outer non-woven shell is made separately, sewn or ultrasonically bonded, with handles, panels and closure attached. Then the liner goes inside the shell and the two are joined only at the mouth, where the join sits above the water line. Our comparison of ultrasonic welding and stitching covers the shell side of that decision in more detail.

Two details to check on a sample. First, the corners: a welded bladder has folded and welded corners, and if you can see a stitch line in the base you have a sewn liner. Second, the mouth join, where the liner is turned over and captured. If it is only tacked in a few places the liner sags and pulls away from the wall, leaving an air gap at the top of the bag that convects freely.

The closure decides more than the foam

Once the wall is sound, everything depends on how well the bag shuts.

A zip is convenient and leaky. Even a good nylon coil zip is a row of interlocking parts with air paths between them, and the tape sides conduct heat straight through the wall. A single zip across the top of a cooler bag is the biggest cold-loss path on the whole product.

A flap over the zip fixes most of it. A hook-and-loop closed lid over a zipped mouth, or a roll-top with a side-release buckle, breaks the direct air path and adds a second wall of foam over the opening. For anything that has to hold overnight, a lid flap is worth more than any amount of extra foam thickness in the panels.

Match the zip to the duty as well. A number 5 nylon coil is fine for a lunch-sized bag. A large delivery bag opened and closed forty times a day wants a number 8, or a moulded resin chain, and a reinforced box stitch at each end where zips actually fail.

Condensation, and the outside of the bag

Cold bags sweat. Air touching the chilled outer surface drops below its dew point and water forms on the fabric, from the outside, with nothing wrong with the liner. Buyers frequently report this as a leak.

Plain spunbond absorbs that moisture and shows it as dark patches, holds it against the foam, and in a warm humid warehouse will grow mould in the base where water collects. A laminated outer shell shrugs it off and wipes clean, which is one reason nearly all cooler bags use laminated fabric rather than plain. The other reason is print: full-colour artwork needs the film.

For bags standing on wet floors, specify the base separately. A PE or PVC base panel, or a stitched-in board in a wipe-clean sleeve, stops the base wicking. Ask for the base construction explicitly, because it is the first component quietly downgraded when a price target is tight.

Weight, handles and the base

A cooler bag is loaded far heavier than a promotional tote of the same size. Twelve litres of chilled drinks with two gel packs is 12 to 14 kg, and that load is dead weight swinging from two handle roots.

Self-fabric welded handles, standard on a light non-woven tote, are not adequate here. What holds is sewn webbing, 25 mm or wider, carried down the side of the bag and either taken under the base or bar-tacked into a reinforcement patch, so the load path runs through the webbing rather than through the fabric. A handle that stops at the mouth hem tears the mouth hem out.

Base support matters at that weight too. Without a board the base bows, the corners crease against the same fold lines every trip, and the liner cracks exactly there. A removable board in a sleeve lets the bag still fold flat for shipping. If you are working out finished dimensions, our guide to sizes and gussets covers how the gusset and base interact, and remember the insulated wall eats 8 to 15 mm of internal width on each side.

“How many hours?” The honest answer

Suppliers quote hold times freely. Treat the numbers with caution, because the bag is only one of five variables.

The cold source dominates. Water ice and gel packs absorb roughly 330 kilojoules per kilogram as they melt, so the mass you load decides how long you have far more than the wall does. A rough working figure is 10 to 20 per cent of the payload weight in cold packs for a half-day, more for longer.

How full the bag is comes next. Air has almost no heat capacity, so a half-empty cooler warms quickly and every opening exchanges the whole void. Filling the space with crumpled paper or an extra pack materially extends hold time.

Then ambient temperature, opening frequency, and whether the contents went in already chilled. A bag loaded with room-temperature drinks is being asked to do refrigeration, which it cannot do; it can only slow the drift.

A defensible specification therefore reads like this: with the bag filled to 90 per cent, two 400 g gel packs pre-frozen to minus 18 degrees Celsius, ambient 32 degrees, lid opened twice, the core stays below 8 degrees for X hours. That is a measurement. “Keeps cold for 12 hours” is a hope.

Testing before you approve the sample

Four bench tests catch nearly everything, and none of them needs a laboratory.

Temperature profile. Put a small data logger in the geometric centre, load the pack pattern you actually use, log a second channel for ambient, and leave it for the duration of a real delivery cycle. Test two bags, not one. This is the bench version of the packaged thermal test described in ASTM D3103, and run consistently it lets you compare a revised sample against the original on equal terms.

Water hold. Half fill the liner with water, stand the bag on dry paper for thirty minutes, then check the paper and squeeze the base seams. Any damp means the liner is perforated or the weld is incomplete.

Fold and crease. Fold the bag flat as it would ship, unfold, repeat twenty times, then hold the base corners up to a bright light from inside. Pinholes on the crease lines mean the foil is too brittle for the pattern or the corner needs a radius.

Load. Fill to 1.5 times the intended weight, lift by the handles and carry it fifty metres, then look at the handle roots and the mouth hem rather than at the handles themselves. Cycle the zip a hundred times while you are at it.

Food contact and documentation

If food touches the liner directly, the inner skin needs to be a food-contact grade and the paperwork needs to exist. Polyethylene inner faces are common and ordinarily suitable, but suitability comes from the laminator’s declaration for that specific grade and its additives, not from the fact that the material is polyethylene.

Ask for the material declaration before the order rather than after, name the market it has to satisfy, and keep the reference with the specification. Any certification is held by the mill or converter and arranged per order, with the certificate number confirmed in writing before a claim appears on artwork or packaging. Where food goes into its own primary packaging first, this becomes a much shorter conversation, and saying so at enquiry can simplify the build.

What a cooler bag specification needs

A cooler bag enquiry needs more lines than a plain tote, because there are two assemblies rather than one. A specification carrying these points can be quoted properly instead of guessed at.

• Outer shell: fabric weight in gsm, laminated or plain, and the print method with colour count and Pantone references.
• Liner: metallised film or true aluminium foil, and the layer structure of the laminate.
• Foam: type (EPE, XPE, EVA) and thickness, and whether the walls, base and lid all carry it.
• Liner seams: welded, and whether the liner is a separate bladder or bonded to the shell.
• Closure: zip size and type, plus any lid flap, hook-and-loop or buckle over it.
• Handles: webbing width, whether it wraps the base, and reinforcement at the roots.
• Base: board or no board, removable or fixed, and any wipe-clean or waterproof panel.
• Internal dimensions you need, not external, since the wall consumes the difference.
• Duty cycle: single use, occasional, or daily commercial handling.
• Performance target as a measurable profile, with your pack pattern, ambient temperature and acceptable core temperature.
• Food contact, if any, and the market whose documentation you need.
• Packing, marks, destination port or delivery address, and your Incoterm.

Bags outside a standard catalogue shape, moulded builds and unusual liner structures go through our custom and OEM service. Send the specification through the quotation form and we usually reply within one business day.

Frequently asked questions

How many hours will an insulated cooler bag hold temperature?

The bag alone does not set the figure. Hold time is decided by the mass of the cold source, how full the bag is, ambient temperature and how often it is opened. A 4 mm foam bag packed full with gel packs at roughly 15 per cent of the load weight behaves very differently from the same bag half empty on a loading bay. Ask for a temperature log against your own pack pattern rather than accepting a number in hours.

What is the difference between a metallised film liner and a true aluminium foil liner?

Metallised film, usually VMPET, carries an aluminium layer a few tens of nanometres thick, vacuum-deposited onto polyester. It looks bright and costs less. True foil is rolled aluminium around 6.5 to 9 µm thick, so it reflects more, blocks water vapour completely and does not lose its metal layer when scuffed. Foil is also more brittle at a fold, which is why crease lines matter in the pattern.

Is the insulated liner sewn or welded?

On a well-built bag the liner is welded and the outer shell is sewn. A needle hole in a liner is a leak path for meltwater, so the liner seams are heat- or high-frequency welded through the polyethylene skin of the laminate. The non-woven shell is then sewn or ultrasonically bonded separately and the liner is fitted inside it.

Can a cooler bag be printed in full colour?

Yes, if the outer shell is laminated non-woven. The artwork is printed on BOPP film which is bonded to the fabric, so photographic images and gradients hold and the surface wipes clean. Plain spunbond takes screen printing well for solid spot colours but not fine four-colour work.

Can food go straight into the liner?

Only if the inner skin of the laminate is specified for food contact and the material declaration is on file. Most liners have a polyethylene inner face, which is a common food-contact polymer, but the grade and any additives still need documentation from the laminator. Certification is held by the mill or converter and arranged per order, with the certificate number confirmed in writing before any claim is printed on packaging.

A buyer approves a sample, signs off a Pantone reference, then opens the bulk shipment to find a bag half a shade off and stiffer in the hand. Nine times in ten, that colour and that hand-feel were fixed at a fabric mill weeks before anyone printed anything.

This is how a non-woven bag is made, from resin to marked carton, and what becomes permanent at each stage.

It starts as a pellet, not as cloth

Spunbond non-woven begins as polypropylene homopolymer pellets. Homopolymer, not copolymer: the regular chain structure holds the molecular orientation the drawing stage imposes, and that orientation is the fabric’s strength.

Grade selection turns on melt flow index (ISO 1133). Spunbond grades sit around 25–40 g/10 min. Higher MFI lowers melt viscosity, so the polymer clears spinneret capillaries a fraction of a millimetre across and spins finer filaments; too high and filaments snap during drawing, too low and the fabric comes out coarse and boardy at the same weight.

Colour is added here, which is what buyers most often misread. Pigment arrives as masterbatch — colourant concentrated in a polypropylene carrier — dosed into the extruder feed, so the colour lives inside the filament. Non-woven is body-coloured, not surface-dyed: the shade runs through the cross-section, it does not crock onto a white shirt, cut edges match the face, nothing washes off.

The constraint is the other half of that fact. You choose from a shade card rather than commissioning a colour, because an arbitrary Pantone in the fabric body needs its own masterbatch and a spinning run for your order alone. The usual answer is the nearest stock shade, with the brand colour in the print.

The spunbond line, from melt to wound roll

It all happens inside one continuous machine: no yarn, no loom, melt to wound roll in seconds. Pellets and masterbatch feed a single-screw extruder, where the polymer melts at roughly 220–250 °C, passes a screen changer and is metered by a gear pump into a spin beam, which forces it through a spinneret carrying thousands of capillaries. Quench air cools the filament curtain, then aerodynamic drawing attenuates the filaments in high-velocity air to around 18–25 µm and orients the polymer chains along the fibre axis. An under-drawn spunbond is weak however heavy it is.

The filaments land at random on a moving perforated belt with suction beneath, and at that instant the basis weight is fixed — throughput divided by belt speed and width. Nothing downstream adds it back.

The web becomes fabric at the calender: two heated steel rolls, one engraved with a raised point pattern, one smooth, pressed together near the softening point of polypropylene. Where a point presses, the filaments fuse into a weld; elsewhere they stay loose, so only a tenth to a quarter of the surface is bonded.

That pattern is a specification variable, not decoration. Larger bond area raises tensile and abrasion resistance but gives a stiffer, papery hand and worse tear, because welded rows act like perforation lines; finer dots give softer drape and better tear at the cost of fuzzing. Under-bond and fibres pull out under a fingernail; over-bond and the welds go glassy, so the fabric splits along the pattern. The web is then trimmed, slit and wound.

What “non-woven” changes about the finished bag

The name is literal: no warp, no weft, no interlacing, no yarn. Strength comes from a random filament network anchored at thermal welds, and three things follow for bag design.

It is directional despite looking random. Airflow and belt travel bias the filaments, so machine-direction tensile strength typically runs about 1.3 to 2 times the cross-direction figure. Panels are nested with the machine direction vertical, along the line of the hanging load.

Tear propagates differently. In woven cloth a tear is arrested by the next yarn; here there is none, so a crack runs between weld points with little resistance. A nick in a raw edge travels further than buyers expect, so a handle root needs a reinforcement patch or a bar-tack.

Cut edges do not fray. With no yarn ends to unravel, a hot-knife or ultrasonic cut ends sealed by its own melt, so no hemming is needed. That is much of why conversion is cheap, and why a D-cut bag, whose handle is punched out of the body, can exist at all.

Two things the roll fixes: weight and width

Basis weight in grams per square metre governs stiffness, opacity, how the bag stands and how much load the panels and welds carry. It is checked by cutting a known area and weighing it: a roll running a few grams light is invisible to the eye and obvious on a balance. Our guide to fabric weight covers choosing the figure.

Roll width is the variable buyers never think about, and it quietly moves price. The flat blank — body panels plus gusset, hem and seam allowances — has to nest into the slit width; if every repeat leaves a broad strip of offcut, you are buying fabric for the bin. A centimetre or two of change in bag width often lands the layout on a cleaner division of the roll, so if your dimensions carry tolerance, say so at enquiry.

The print decision: on the fabric, or under the film

This fork sets cost structure, artwork limits and durability at once. Our article on print methods and what drives their cost ranges wider; here is how it lands on spunbond.

Route A: print onto plain fabric. Screen printing is the workhorse — one mesh screen per colour, water-based or polyurethane ink pulled through onto the panel, then cured in a drying tunnel. It suits solid spot-colour blocks, logos and line art over few colours; cost scales with colour count rather than area, and registration is mechanical rather than optical, so tight multi-colour detail is the wrong brief. Heavy coverage stiffens the panel and can crack on a fold. Heat transfer handles fine detail over a small area but leaves a patch with a defined edge; flexography prints water-based ink on the roll before conversion. All three meet the same limit: the substrate is porous, ink sinks between filaments and reads duller than on coated paper, so approve a printed fabric drawdown, never a paper chip.

Route B: print the film, then laminate it. For laminated non-woven bags the artwork never touches the fabric. It is gravure printed in reverse on BOPP film, an engraved cylinder per colour, four-colour process plus spot colours, then bonded to the spunbond by dry lamination — adhesive coated, solvent driven off, nipped — or by a solvent-free thermal process. The image ends up sandwiched under the film: photographic quality, gradients, tight registration, ink nothing can abrade.

The commercial logic follows the tooling. Every colour needs an engraved cylinder, paid once and spread across the run, and the press consumes a run-up length of film before colour stabilises whatever the order size. So the route rewards quantity and complex artwork, and is the wrong answer for a two-colour logo on a modest run. Laminated fabric is also not practically recyclable, since film and substrate cannot be separated.

Two routes through the forming shop

The automatic bag machine. The roll unwinds, folds longitudinally to form the body, and the seams close by ultrasonic welding: a horn vibrating at around 20 kHz drives the fabric against a patterned anvil wheel, and interfacial friction fuses the polypropylene. No thread, no needles. Handles are welded on the same pass, or on a D-cut line the aperture is punched out of the body, and a cross-cut releases the bag.

It is fast and consistent, and it is where standard shapes belong: D-cut, vest styles and loop-handle non-woven shopping bags. The constraint is geometry — sizes step in the increments the tooling allows, gusset range is limited by the folding board, handle position is where the machine puts it. Too little weld amplitude gives a cold weld that peels; too much and the horn cuts the fabric.

The semi-automatic and hand line. Fabric is laid up in plies, cut to pattern by die or hot knife, and the panels joined by sewing with polyester thread, by ultrasonic welding, or both. Handles go on with a box-and-cross stitch or a reinforced weld, base boards drop in, and the bag is turned by hand.

Tooling here is a paper pattern rather than a machine change, so this route absorbs anything irregular: box bags with a separate base panel, wine carriers with dividers, cooler bags with a foil liner, added reinforcement, any construction with a zip. It carries more labour per bag and more unit-to-unit variation than machine welding, a limitation worth accepting knowingly rather than discovering. Sewn seams perforate the fabric, so bar-tacking the handle root matters.

Finishing, and where it collides with the fabric

• Base insert — a cut card or PP sheet in a base pocket, loose or stitched in, so the bottom stays flat under load.
• Four-sided forming — pressing the vertical corners so the bag stands square instead of slumping.
• Window — a die-cut aperture with clear PET or PVC film welded behind it; the cut edge is cleaner on laminated fabric.
• Zips, hook-and-loop tabs, cord channels and cord locks — zips are sewn rather than welded, because welding a zip tape reliably is harder than it looks; a drawstring channel is a folded hem closed before the cord is threaded.

Hot foil stamping behaves differently on the two substrates. Foil needs a smooth, closed surface to key onto. Plain spunbond is fibrous and porous, so foil transfers only to the raised bond points, reads as mottled and survives folding badly. On a laminated face the BOPP film gives exactly the continuous surface the process wants, and the result is crisp. Spot UV follows the same rule, so a brief calling for metallic detail or selective gloss has already chosen laminated fabric.

Where the quality gates actually sit

Inspecting only at the end tells you how much you have already lost. The gates that matter sit along the line.

1. Incoming fabric. Basis weight by cut-and-weigh under ISO 9073-1, slit width, roll-to-roll colour against the approved swatch, and a visual pass for holes, streaks, unbonded patches and oil marks.
2. Print first article. Registration, coverage and position measured from the bag mouth and side seam. Colour is judged in a light booth under a D65 standard illuminant, cross-checked under store lighting for metamerism, and quantified with a spectrophotometer as a Delta E value against the signed swatch. Around Delta E 3 is realistic on a porous substrate.
3. Forming first-off. Width × height × gusset measured flat, handle length and centres checked, and a pull test to confirm the fabric fails before the weld does.
4. In-process patrol. Dimensions, weld quality and print position re-checked at intervals, so drift is caught early.
5. Final random inspection. Sampling to ISO 2859-1 general inspection level II, commonly AQL 2.5 major / 4.0 minor, drawn from packed cartons. What counts as major is agreed in writing beforehand.
6. Cartoning. Inner count verified, carton gross weight compared against the calculated figure so a short count shows as a light box, and dimensions checked against the packing list.

Our role sits across those gates rather than at the machines: production runs through an SGS-verified facility in Wenzhou, and we fix the specification, run sampling, hold the signed reference at the line, check each first-off and inspect before shipment. Our quality policy sets out what gets checked, and our notes on vetting a non-woven bag manufacturer cover what to ask first.

Why the sample and the bulk are never identical

A pre-production sample and a production bag are made by different means: the sample is often screen printed by hand and assembled by a sample maker, while the bulk may be gravure printed, machine welded and die cut. Hand and machine registration do not give the same edge quality, and a hand-sewn handle does not feel like a welded one.

Fabric adds a second gap: masterbatch dosing and spinning conditions drift between lots, so a nominally identical shade shifts from batch to batch. Dimensional tolerance is a third — the fabric is compressible and cutting is done through a stack, so roughly a centimetre of variation on a mid-sized bag is normal rather than defective.

What controls all three is a signed reference sample in duplicate, one copy in the order file and one at the line, plus a written specification with explicit tolerances for dimensions and colour. Both sides also need to agree what the sample approves: if it was built before the bulk fabric was bought, approve shape and construction from it, but approve colour separately against a swatch cut from the production lot.

Packing, marks and the container

Non-woven bags are light and bulky, which inverts the usual freight arithmetic. Air and courier shipments price on volumetric weight, and LCL sea freight on cubic metres, so carton cube discipline matters more than saving grams.

Inner packing is a count decision: bags bundled into a poly bag or banded, the count stated on the inner label and chosen to divide cleanly for the receiving warehouse rather than for convenience on the line. Bags compress, but over-compressing laminated fabric sets creases into the film that will not fall out on the shelf.

Shipping marks should be approved as artwork before packing starts, because re-marking cartons at the port is slow and expensive. They normally carry item and colour, size, quantity per carton, carton number out of total, gross and net weight, carton dimensions, the order reference, the destination and any retailer-mandated labelling such as a GS1 barcode. Carton size matters too: a box slightly too tall to stack another tier inside the container height wastes cube on every unit shipped.

What to send with an enquiry

Quotations vary largely because suppliers are quoting different processes. A specification carrying these points can be priced properly instead of guessed at.

• Material and fabric weight in gsm, or simply what the bag has to carry.
• Finished dimensions as width × height × gusset, stating whether height includes the handle.
• Bag type: D-cut, loop handle, vest, box bag, drawstring, wine carrier, cooler.
• Print method, colour count, vector artwork, Pantone references, print size and position on each face.
• Plain or laminated, and whether foil or spot UV is wanted.
• Handle type: welded self-fabric, sewn webbing, rope with knot or barrel lock, or die-cut.
• Finishing: base board, window, zip, hook-and-loop, gusset construction, reinforcement.
• Packing, marks and any retail labelling standard you must meet.
• Destination port or delivery address, and your Incoterm.
• Whether you need material documentation. Any certification is held by the mill or converter, arranged per order, with the certificate number confirmed in writing before a claim is printed.

If the construction is not in a standard catalogue, our custom and OEM service covers pattern development and bespoke builds. Send the specification through the quotation form and we usually reply within one business day.

Frequently asked questions

Why can I not get an exact Pantone match on non-woven fabric?

The colour is spun into the fibre, not applied to the fabric. Masterbatch is dosed into the extruder before the filaments form, so a body shade is picked from the mill’s card rather than mixed to order. Put the exact brand colour in the print, where ink can be mixed.

Are non-woven bags sewn or welded?

Both, depending on the route. Standard shapes such as D-cut and loop-handle totes run on an automatic machine that welds seams and handles ultrasonically, with no thread. Irregular shapes, box bags, zips and reinforced constructions go down a semi-automatic or hand line, where panels are cut to pattern and sewn, welded, or both.

What does GSM actually control, and how is it verified?

GSM is grams per square metre, fixed on the spunbond line by polymer throughput divided by forming belt speed. It drives stiffness, opacity, tear resistance and how much load the panels carry, and is verified by cutting a known area and weighing it under ISO 9073-1.

Do I need laminated fabric for full-colour printing?

For photographic images, gradients and tight four-colour work, in practice yes. That artwork is gravure printed on BOPP film which is then bonded to the spunbond, so the image sits under the film. For solid spot colours and line art, screen printing on plain fabric is simpler and avoids cylinder engraving.

Why do the cut edges of a non-woven bag not fray?

There are no yarns to unravel. The fabric is a random web of continuous filaments fused at thermal bond points, so a cut edge simply ends and no hemming is needed. The trade-off is that a nick in a raw edge propagates further than in woven cloth, so handle roots are reinforced.

A buyer sends over a photograph of a non-woven tote with one handle hanging off. The weld has peeled open along its whole length, like a label lifted, and the fabric either side is untouched. The bag was ordered as “heavy duty”, it passed visual inspection, and the purchase order said nothing about how the handle was to be attached. There is no claim to make, because there was no requirement to breach.

How panels are joined decides how long a bag survives, and it is the line most often left blank on a specification. Here is what ultrasonic welding does to spunbond polypropylene, what stitching does instead, where each fails, and how to write the requirement down.

Why spunbond polypropylene can be welded at all

Non-woven PP is not a fabric in the textile sense. Molten polypropylene is extruded through a spinneret into continuous filaments, laid randomly onto a belt as a web, then consolidated between a heated engraved calender roll and a smooth roll. Those calender marks are the small diamonds visible when you hold 80 gsm spunbond up to a window: the web is held by thousands of tiny thermal bonds, not by weaving.

The consequence that matters is that the whole material is thermoplastic. PP homopolymer melts around 160–165 °C, so filaments at an interface can be re-melted and left to re-solidify as one mass. That is not glue or adhesion: it is polymer chains from two layers interdiffusing and crystallising together on cooling. Done properly, the joint is not a joint but one continuous piece of plastic.

The four settings that decide whether a weld holds

A generator converts mains supply into a high-frequency signal, most commonly 20 kHz for bag work. A piezoelectric converter turns that into mechanical vibration, a booster scales it, and a horn, or sonotrode, presses it into the material against a patterned anvil. On a bag line the horn is a rotating wheel over an engraved anvil wheel, so fabric runs continuously through a nip.

The motion is vertical and very small, typically 20–60 µm peak to peak at the horn face. Friction between the fabric faces and hysteresis within the polymer generate heat in a fraction of a second, concentrated on the raised anvil points, which act as energy directors. Four variables control the result:

• Frequency. 20 kHz is the workhorse: high amplitude, high power, tolerant of heavier stacks. 35 or 40 kHz give smaller amplitude and a gentler weld, useful on thin webs and laminates.
• Amplitude. Set by booster and horn gain, this is the energy per cycle — the fastest route to a burnt-through panel, and to an unwelded one.
• Nip force. Pressure couples the horn to the fabric and holds the melt in compression while it solidifies. Too little and energy bounces off; too much and the horn crushes the fibre structure and thins the joint.
• Dwell time. On a rotary system dwell is contact arc divided by line speed, which is why a setting that worked yesterday fails once an operator raises the output rate. The weld window moved; nothing else did.

A fifth variable matters just as much: the anvil pattern. Discrete dots give a flexible seam with modest peel strength; a dense lattice or continuous embossed band gives higher shear strength but a stiffer, more brittle line. Unfused fibre between the weld points lets a seam flex and share load.

What ultrasonic welding is genuinely good at

There is no needle and no thread, so nothing unravels: a broken stitch propagates along a seam, a failed weld point stays local. The process runs in line with the bag machine, forming side seams, bottom and gusset in one automated pass at a rate no sewing room approaches — the main reason machine-made non-woven shopping bags cost what they do. The horn cuts and seals in one action, so edges do not fray, and because the fabric is never perforated there is no needle-hole leak path, which matters on laminated non-woven bags where the film is doing a barrier job.

Where ultrasonic welding lets you down

A weld is a brittle joint. Inside the welded zone the fibre architecture is destroyed and replaced by re-solidified bulk polymer with no fibre-to-fibre give. Loaded in shear, along the plane of the seam, that is fine and often stronger than the fabric next to it. Loaded in peel — two layers pulled apart at an angle — or at a concentrated point, it is markedly weaker than stitching. A handle root is exactly a peel-and-point load, which is why it is the classic failure site.

There is also a notch effect: the boundary between hard weld and soft fabric is a step change in stiffness, so tears often start at the edge of the weld rather than within it. Over-welding turns the seam glassy and hard, and the line cracks when creased. Under-welding leaves layers that separate under finger pressure while passing visual inspection. Neither is repairable — a stitched seam can be unpicked and resewn, but welded material has already been converted, so rework means scrapping the panel.

The weld window also moves with the fabric. Melt flow index, fabric weight, calender bond area, colour masterbatch and above all calcium carbonate filler all shift it. Filler does not melt; it absorbs energy and seeds weak spots, so heavily filled low-cost fabric welds inconsistently, and recycled content narrows the window further. Heavy screen ink at a weld line acts as a barrier and prevents interdiffusion, so keep artwork clear of the seam by 8–10 mm. On laminated stock the BOPP film shrinks and blisters at temperatures the substrate tolerates comfortably, and gloss film shows scorch that matt film hides.

What stitching buys you, and what it costs

Stitching anchors thread through the fabric at many discrete points, so load distributes across all of them, the fabric between them shares it, and failure is progressive — a stitch at a time, with visible warning — rather than one sudden separation. That is why peel and tear resistance are so much better. It is also adjustable: thread ticket, stitch type (301 lockstitch, 401 chainstitch, 504 overlock, 516 safety stitch), stitch density, needle size and seam allowance are independent levers, and stitching permits construction welding cannot produce — bound edges, turned hems, boxed corners, a patch behind a handle, webbing down the side wall. Above all, a sewn handle root can be worked as a box-X or bar-tack, spreading load across a rectangle rather than a line, which is why heavier non-woven tote bags almost always contain some sewing.

The cost is labour: every seam is operator time, and the sewing room becomes the constraint on output. A needle hole is also a defect you choose to create — each penetration weakens the fabric locally, and pushed too far the seam perforates like a postage stamp and tears along its own stitch line. Every hole is a water path, so sewing a laminated bag partly undoes the reason for laminating it, and a blunt or overheated needle can fuse spunbond into a run of melted holes. Add skipped stitches, thread breakage, loose bobbin tension, seam pucker, alignment that depends on the operator, and thread with its own abrasion and UV behaviour.

The hybrid build, and when it earns its cost

Most well-built machine-made bags are not purely one thing. The standard hybrid welds the body on the automatic line, then reinforces the handle roots with a sewn box-X or bar-tack through handle and panel, a welded patch behind the root, or both. Some builds add a strip running under the base and up both side walls, so handle load transfers into the base rather than into two small welds.

It earns its cost when the rated load is real rather than nominal, when the bag carries bottles or glassware, when it is meant to be kept and reused, when it will hang from a shoulder (dynamic loading repeatedly peels the root), or when the retailer runs a documented pull protocol at goods-in. It does not earn its cost on a lightweight giveaway, and we would rather say so than upsell it.

Bag type decides the method, and canvas decides it for you

D-cut bags have no handle joint at all: the handle is a die-cut aperture, so strength is the tear resistance of the fabric around the cut-out, not a seam — the answer to a weak D-cut bag is heavier fabric, not better welding. T-shirt and vest bags are similarly welded throughout, limited by the fabric at the base of the loop. The classic machine-made handle bag, where a separate loop is welded onto the mouth, is the cheapest construction and likeliest to fail at the root. Box bags carry more, and above roughly 90–100 gsm they commonly move to a hybrid or fully sewn build with a bound top edge; our fabric weight guide covers how weight and construction interact.

Cotton canvas bags settle the question outright. Canvas is woven cellulose: cotton does not melt, it chars, so ultrasonic energy only abrades and scorches without forming a bond. Every seam on a genuine canvas tote is sewn, and the strength conversation moves to fabric weight in ounces, thread ticket, stitch density and webbing. A useful test: if something is offered as canvas with welded seams, it is not cotton.

Testing the joint: pull, peel and drop

Three tests cover almost everything, and one rule of interpretation matters more than the numbers.

Handle pull. The workshop version loads the bag to rated weight, lifts it clear by both handles, holds for 60 seconds, then repeats the lift-and-lower cycle; 100 cycles is a reasonable benchmark for a reusable bag. The instrumented version clamps handle and body in opposing jaws of a tensile tester, pulls at a constant crosshead speed such as 100 mm/min, and records peak load in newtons. Draw samples across the run, not off one carton.

Seam peel. Cut a 25 mm strip across the seam, clamp each layer in opposing jaws, pull them apart and record average force per unit width in N/25 mm. Peel is the measurement most sensitive to weld setting, and the best early warning that the line has drifted. A grab test across the same seam gives the in-plane figure.

Drop. Fill to rated load and drop flat and on each bottom corner from a defined height such as 750 mm.

Now the rule: where it broke is more diagnostic than what it read. Fabric tearing with the seam intact means the joint is stronger than the material; to go higher, change fabric weight, not machine settings. A clean separation with a polished, glassy face means over-welding. A fuzzy peel with only part of the anvil pattern transferred means under-welding or poor coupling. A tear running along the weld boundary means the notch effect dominates, so reduce amplitude or widen the pattern. Handle webbing snapping while the bag is undamaged means the handle material, not the joint, is the limit. “Handle pull, both handles, 100 mm/min, n = 5, all failures in fabric” tells you something; “passed” does not.

A defect atlas, read backwards to the machine

• Hard, whitened weld points that crack when creased — over-weld: excess amplitude or nip force, line speed too low, or a worn anvil.
• Seam that opens under thumb pressure — under-weld: low amplitude, line too fast, insufficient force, or ink, dust or silicone contamination.
• Pinholes or burn-through along the weld — amplitude and pressure both too high, or a hard inclusion in the web.
• Weld wandering off the edge, pattern half missing — feed and web tension: unwinder imbalance, worn guides, panel misalignment.
• Puckered or blistered film on a laminated bag — BOPP shrinkage; the setting suits the substrate but not the film.
• Skipped stitches, loops underneath, broken thread — needle and thread selection, machine timing, tension, or a burr on the throat plate.
• Tearing along the stitch line — stitch density too high or needle too coarse for the fabric weight.
• Asymmetric handles — a cutting or alignment error; the shorter side takes disproportionate load and fails early, so it is a strength defect, not a cosmetic one.

Writing the joining method into your specification

“Good quality, strong handles” cannot be inspected against. Five lines make it enforceable:

• Body joining method — ultrasonic weld, anvil pattern, weld band width (6 mm, say) and its position relative to the cut edge; or sewn, with stitch type and seam allowance.
• Handle joining method — welded, sewn, or welded plus a sewn box-X bar-tack at each root, with thread and stitch density stated (Tex 40 spun polyester at 10 stitches per inch is a sensible default).
• Reinforcement — whether a patch is required, its material, size (40 mm × 50 mm, say) and placement, and whether the handle passes through it or sits on top.
• Rated load and acceptance by failure mode — the load, the number of lift cycles, and an explicit statement that fabric tear is acceptable while seam separation or handle detachment is a reject.
• Inspection plan — first article approval against a signed retained sample, in-process patrol with a hand-peel check on each machine, and final random inspection to ISO 2859-1, general inspection level II, AQL 2.5 major / 4.0 minor.

That last point deserves emphasis: most seam disputes are not about whether a defect exists but about whether it was major or minor, so classify handle detachment and seam separation in writing before production starts; our quality and inspection approach sets out how first article, patrol and final inspection fit together. Four things let us answer a seam question properly: what the bag will carry and how heavy, whether it is a handout or meant for repeated use, whether the retailer runs its own pull protocol, and whether artwork comes near the seam lines. Send those through our quotation form and we usually reply within one business day.

Frequently asked questions

Is an ultrasonic weld as strong as a sewn seam?

It depends on how the load arrives. In shear, along the plane of the seam, a correctly set weld is usually stronger than the fabric beside it. In peel, and at point loads such as a handle root, stitching is clearly better: it anchors through the fabric and fails progressively rather than all at once.

Can canvas bags be ultrasonically welded?

No. Cotton canvas is woven cellulose: it does not melt, so there is nothing to fuse, and ultrasonic energy only abrades and scorches it. Every seam on a cotton canvas bag is sewn. If a bag is offered as canvas with welded seams, the fabric is a synthetic.

Why do non-woven bag handles fail at the root?

The root sees peel and point loading, the weakest direction for a weld, and the boundary between hard weld and soft fabric is a stiffness step that concentrates stress. A box-X bar-tack or a reinforcement patch spreads that load over an area instead of a line.

What does a hard, glassy weld point tell me?

It is over-welded: too much amplitude, too much nip pressure or too slow a line has melted more polymer than the joint needs and destroyed the fibre structure, so the seam is brittle and cracks when flexed. Under-welding is the opposite — layers peel apart fuzzy under finger pressure.

How should the joining method be written into a specification?

State the body joining method and weld pattern, the handle method including any reinforcement patch or bar-tack, thread and stitch density if sewn, the rated load, and the acceptance criterion by failure mode — fabric tear acceptable, seam separation a reject. Add the inspection plan and the AQL.

A shipment lands, the bags measure exactly what the drawing said, and the gift box they were bought for will not go in. Nobody lied: the buyer measured the box, the converter built to the specification, and the specification described a different bag from the one in the buyer’s head.

Almost every dimension dispute traces to three causes — the order the numbers were written in, where the tape measure was placed, and clearance nobody allowed for.

What the three numbers actually mean

Width is the face panel as the bag hangs in front of you. Height runs from the finished top edge to the base, measured on the face panel and excluding handles. Gusset is the depth — how far the bag opens out at the sides, the base, or both.

The trouble is the sequence. Asian converters write width × height × gusset. The North American paper bag trade follows the corrugated carton convention — width × depth × height — so 8 × 4 × 10 is a bag eight inches across the face, four deep and ten tall. Some European buyers use width × gusset × height. Unlabelled, 35 × 12 × 40 is 40 cm tall under one convention and 12 cm tall under another, and both readings are defensible.

Two traps sit underneath. Some drawings quote the gusset as the total expanded depth, others the half-gusset, the fold depth on one side, so “gusset 5” can arrive 5 cm or 10 cm deep. Units drift too: twelve inches is 30.48 cm, not 30 cm.

The fix costs ten minutes: a dimensioned drawing with every figure labelled by name and the unit printed on it. Contradictions then surface at quotation, not at inspection.

Flat, opened, outside, inside: fixing the datum

Lay-flat measurement is taken with the bag pressed flat and the gusset folded in, which is how inspections are done; opened measurement is taken with the bag pushed out square. On a side-gusseted bag the two differ, because the folded gusset sits inside the flat outline. State which basis applies.

Outer versus internal is the other half. Quoted sizes are almost always outer, and thickness adds up: 80 gsm spunbond runs around 0.4 mm, a BOPP lamination adds 15–20 µm of film plus adhesive, and a hem doubles it locally. On a cooler bag an EPE foam and foil layer of 2–5 mm per wall removes up to a centimetre from internal width and depth, so quote the cavity explicitly. Stiffness compounds it: a plain 80 gsm bag deforms around a slightly oversized box, but a laminated shopping bag does not.

Then tolerance. Hand cutting and operator-guided sewing mean hand-assembled bags run looser than automated ones: plus or minus 1 cm on width and height and 0.5 cm on the gusset is ordinary practice for a stitched bag, while tighter is realistic on machine-made D-cut bags and T-shirt bags, die-cut and heat-sealed in one pass. Tolerance is a technical figure, not a promise: put it in the specification sheet and let the quotation confirm it. Clearance must then be at least as large as tolerance.

Three ways to build a gusset

Gusset describes an outcome, not a construction. A bottom gusset, or box bottom, folds and seals the base so the bag has a rectangular footprint and stands; it adds capacity where the weight sits, which is why even light D-cut giveaways often carry a shallow one. A side gusset is a full-height fold down each side — the cheapest volume there is, and dead flat for shipping, but with a plain base seam it slumps into a V rather than standing empty.

A four-panel box bag is a true rectangular prism: front, back, two sides and a folded or attached base. Corners are square and it stands full or empty, but it costs more — more cutting, more seaming, usually a lamination to hold the shape. Box bags suit rigid contents and shelf presentation.

Two accessories matter: a base insert of PP board keeps a soft bag flat-bottomed but eats internal height and must be specified loose or sewn in; a bottom reinforcement strip spreads load along the base seam rather than the corners, where failures start.

Matching the bag style to what goes inside

Construction limits the sensible size range. D-cut bags carry load through a die-cut opening, so the fabric bridge between cut and top edge — typically 2.5–3.5 cm, and only safe in a doubled hem — is the whole load path; they suit light distribution with no gusset or a shallow base fold. T-shirt bags pair vest handles with a side gusset for checkout; stitched-handle totes cover the retail middle; box bags take books, gift boxes and bottles.

Wine bags need care, because the divider changes the maths: sewn into the base seam it consumes its own thickness plus seam allowance, so cell width is not half the bag width. Bottle diameters also vary — Bordeaux around 76 mm, Burgundy 80–86 mm, sparkling 88–90 mm — so a bag sized around Bordeaux will not take Champagne. Shoe bags follow the box, not the shoe.

Working backwards from the contents

Do not guess a size and test it. Measure the load in the posture it will travel in, then add allowances:

1. Stack the goods as they will really be packed — upright, flat, on edge — and measure the stack as one block.
2. Bag width = item width + about 2 cm of ease.
3. Gusset = item depth + 1–2 cm.
4. Bag height = item height + handle sag + top closure, typically 5–8 cm combined on a soft bag, less on a stiff one.
5. Check the entry diagonal: a rigid box must tip into the opening before it sits down.

A4 conference bag. An A4 folder is 210 × 297 mm, a realistic document stack about 30 mm. Width 21 + 2 = 23, rounded to 24 cm. Gusset 3 + 2 = 5, rounded to 6 so a ring binder fits. Height 29.7 + 6 = 36 cm. That is 24 × 36 × 6 cm; add a gift box and the gusset goes to 8–10 cm, with the fabric weight rising to match.

Single shoe box. An adult box at 33 × 20 × 12 cm, largest face to the front, gives width 35, gusset 14 and height 30 cm once rounded to keep the handle roots clear. Stack two boxes, the gusset jumps to 26 cm, several kilograms load a wide base seam, and the tote becomes a box bag with an insert and heavier fabric.

Two 750 ml bottles. Two Bordeaux side by side occupy about 152 mm, so width 18 cm; the gusset is one diameter plus clearance, about 9 cm; bottles stand around 32 cm, so 35 cm contains the necks. That is 18 × 35 × 9 cm. The constraint here is load: two filled bottles are roughly 2.5 kg on a narrow base seam.

Handles: drop, width and the root

Drop is the vertical distance from the finished top edge to the inside top of the handle loop. Hand carry needs roughly 15–18 cm, clearing a fist and a coat sleeve; shoulder carry needs 25–30 cm so the bag hangs past the hip over outerwear. Specify both the strap cut length and the finished drop, because “handle length” is used for either.

Width is a comfort specification before a strength one: 2.0–2.5 cm suits a light bag, 3.8 cm spreads load across the palm, 5 cm stops a heavy bag cutting in.

The root is where bags fail. Handles rarely part in the middle; they tear out of the panel, taking a crescent of fabric. The countermeasures are cheap at specification stage: a reinforcement patch behind each attachment, a box-with-X bar tack instead of straight stitching, a doubled top hem, or an internal facing strip spreading the pull along the top edge. Ultrasonic welding is fast and thread-free, but the weld is a stiff zone with a sharp transition at its edge, and under repeated loading a stitched handle over a patch generally outlasts it.

Size and load are coupled, and not linearly

The costliest sizing mistake is scaling a working design up without touching anything else. Volume rises with the cube of the linear dimensions: add 20 per cent to width, height and gusset and the bag holds about 73 per cent more. At constant density the load at the handle root rises with it, while the cross-section resisting it is unchanged, being set by fabric weight and reinforcement rather than size.

Fabric weight therefore climbs with size, and a bigger bag usually wants a base insert, a reinforced base seam and a wider handle. Our guide to non-woven fabric weight maps those bands to applications. Enlarging a bag alone is not a saving; it is deferred failure.

What dimensions quietly do to cost

The first driver is nesting. Spunbond runs on fixed-width lines — 1.6 m, 2.4 m and 3.2 m are common — and rolls are slit from them. Your flat blank must tile inside the slit width: one centimetre wider than half of it and you get one blank across instead of two, with the offcut wasted on every metre. That is usually why a converter proposes a size a centimetre or two off your drawing.

The second is packing. The folded footprint follows the flat width and the folds the height allows, so a small change can move bags-per-carton across a threshold, altering carton count and shipped cube. Non-woven bags are light for their bulk, so air freight charges on volumetric weight and sea freight is priced by cubic metre or container: landed cost is set by how many fit in a cubic metre, not by what one weighs.

So ask for carton dimensions and pack quantity at quotation, and compare sizes on delivered cost, not ex-works. Laminated and box constructions compress less, so their cube penalty is larger.

Print area, bleed and the fold line

Keep critical artwork about 2 cm clear of every sewn or folded edge. Screen printing onto a soft, extensible substrate does not hold offset-press registration, so a logo tight to a seam will look off-centre on part of the run.

Never run an image across a gusset fold: the crease breaks the ink film, the two halves sit at ninety degrees once the bag opens, and that line is where ink cracks first. Treat the face panel as one artwork area and each gusset as another. Handles also obscure more than people plan for — stitched roots cover the top of the panel, and a D-cut opening removes the top centre.

Edge-to-edge coverage is unrealistic with direct screen printing, which needs a registration margin around the frame. For full bleed and photographic imagery the route is gravure onto the film before lamination, or a heat transfer; our overview of bag printing methods and cost drivers covers where each belongs. Specify Pantone solid coated references and ask for a strike-off: a spot colour behaves differently on coloured non-woven.

Where a bigger gusset is the wrong answer

Over-specification is at least as common as under-specification. Gusset is not free: on a 35 × 40 cm bag, a 10 cm side gusset adds two panels of 40 × 10 cm — roughly 29 per cent more fabric before the base is counted — plus two seam runs. If the bag carries one brochure at a trade show, that bought nothing.

A deep gusset on a low-weight bag also makes it slump, so contents fall over and the bag looks limp on the shoulder, and a bag whose depth approaches half its width becomes unstable standing. An oversized bag also invites overloading beyond what the handle root was designed for. And if the load is heavy, sharp-cornered, wet or facing long UV exposure, no amount of gusset makes non-woven the right substrate.

Proving it: white sample first, then the specification sheet

Sign sizing off in two steps. First a blank white sample in the actual fabric, weight and construction, with no print: put your real product in it, carry it, stand it empty on a shelf, and tape-measure every figure on the drawing including the handle drop. Only then move to the printed pre-production sample and colour strike-off.

The specification sheet is what makes both samples enforceable. At minimum:

• Style and construction; gusset type (side, bottom, four-panel box); base insert loose or sewn.
• Width, height and gusset with a labelled drawing, the unit, the measurement basis (lay-flat or opened, outer or internal) and a tolerance on each.
• Fabric type and GSM; lamination type and film thickness in µm; colour reference.
• Handle type, material, width, cut length, finished drop, attachment and reinforcement.
• Print method, colours per panel, Pantone references, print area size and its distance from the edges.
• Thread type, stitch density, seam allowance, bottom reinforcement.
• Packing: fold pattern, inner bag, bags per carton, carton dimensions and markings.
• Inspection standard, for example AQL 2.5 major / 4.0 minor, and the destination market.

Our own production runs through an SGS-verified facility in Wenzhou, and this sheet is the document we work from. Send a drawing, or send the product you need to fit and let us work the dimensions back from it — we usually reply within one business day. To start with pricing, the request a quote form is the fastest route; what moves a price is quantity, material, print method, finishing and destination.

Frequently asked questions

Does W × H × G mean the same thing to every supplier?

No. Asian converters write width × height × gusset; the North American paper bag trade and some European buyers follow the carton convention of width × depth × height. The same three numbers can describe two different bags, so always send a dimensioned drawing with every figure labelled and the unit written on it.

Is the gusset the total depth of the bag or half of it?

It should be the total expanded depth, so a 10 cm gusset gives a base 10 cm deep. Some drawings quote the half-gusset, the fold depth on one side only. Write the word “total” next to the figure and show the opened base on the drawing.

How much clearance should I add over the size of my product?

Add about 2 cm to the width, 1–2 cm to the gusset, and for height take the item height plus roughly 5–8 cm for handle sag and top closure. Increase the clearance for laminated or box constructions, which are stiff and will not deform around a slightly oversized item.

Do larger bags need a heavier fabric?

Yes. Volume rises with the cube of the linear dimensions, so adding 20 per cent to width, height and gusset raises carrying volume by about 73 per cent. The cross-section at the handle root does not grow unless you raise the GSM, so scaling up without changing fabric weight or reinforcement is a common cause of handle and base failures.

What handle drop do I need for shoulder carry rather than hand carry?

Hand carry needs a finished drop of roughly 15–18 cm, clearing a fist and a coat sleeve; shoulder carry needs roughly 25–30 cm so the bag hangs clear of the hip over outerwear. Specify both the strap cut length and the finished drop, because the phrase “handle length” is used for either.

A buyer sends artwork with a photographic background and a Pantone-matched logo, asks for 80 gsm non-woven totes, and is surprised when two suppliers quote prices a third apart. The artwork is the reason. What can be printed on a non-woven bag is decided almost entirely by whether the fabric carries a film, and that one decision drags cost, weight, stiffness, water behaviour and end-of-life handling with it.

Lamination is often presented as a finish, the way you would pick gloss or matte on a business card. It is not. It is a change of substrate and a change of print process. Below is what each construction physically is, what it buys you, where it costs you, and how to write the difference into a specification.

What the fabric underneath actually is

Almost every non-woven bag in commercial circulation is spunbond polypropylene. Molten PP is extruded through spinnerets into continuous filaments, drawn and laid down at random onto a moving belt, then passed between heated calender rollers with an engraved pattern. The raised points fuse the filaments where they touch. That is thermal point bonding, and it is why the fabric shows a regular grid of small diamonds.

There is no yarn and no interlacing, which has three practical consequences. Cut edges do not fray, so panels can be raw-cut without hemming. The web is micro-porous, so air and water vapour pass through it. And the machine direction is measurably stronger than the cross direction, so panel orientation on the cutting layout is not arbitrary. Surface chemistry matters too: polypropylene has low surface energy, so printable fabric is corona treated to help ink key in, and that treatment decays in storage.

What lamination actually is

The film bonded to the fabric is BOPP — biaxially oriented polypropylene, stretched in both machine and transverse directions so it is dimensionally stable, clear and dense. For bag work it is typically 12–18 µm. Heavier film exists and is sometimes used on stiff box-style bags, but much above 20 µm the bag stops feeling like fabric.

Two bonding routes are common. In dry lamination, a polyurethane adhesive is metered onto the film by a gravure cylinder, the solvent is driven off in a drying tunnel, and the film is nipped to the web under heat and pressure, then cured. This is the route used when the film has been printed beforehand. In thermal lamination, the film arrives pre-coated with a heat-activated adhesive such as an EVA copolymer and is bonded by heated nip rollers with no solvent stage — faster and cheaper, and normally used for plain film.

Here is the structural point most buyers miss: on a laminated bag the ink is usually not on the fabric at all. The image is reverse printed by rotogravure onto the underside of the BOPP, and the film is laminated ink-side down. The ink ends up sandwiched, protected from abrasion, moisture and handling.

Gloss and matte are the same polymer with a different surface. Gloss reflects specularly, so colours read more saturated and blacks look denser. Matte diffuses the reflection, so the same file prints flatter and slightly lighter and usually needs an ink adjustment. The trade-off buyers underestimate is fingerprinting: the microstructure that makes matte film matte also holds skin oils, so handling marks show, worst across large dark solids. Gloss wipes clean. A matte navy or matte black bag is the commonest source of “the bags arrived marked” complaints.

What lamination buys you

On unlaminated fabric the realistic print options are screen printing, heat transfer and water-based flexo. Screen work dominates because tooling is cheap per colour, but each colour needs its own screen and pass, registration on a soft extensible web is harder than on paper, and fine halftone dots fill in as ink wicks into the fibre. A gradient that fades to nothing plugs at the dark end or drops out at the light end. Four to six spot colours is where screen printing stops being sensible.

Gravure on film is a different world. The engraved cylinder holds line screens far finer than any mesh, so four-colour process, photographic imagery, small serif type and smooth vignettes all reproduce, and run-to-run colour is more repeatable because film does not stretch the way fabric does. The cost sits in cylinder engraving, one per colour, amortised across the run. Our note on print methods and what drives their cost runs the same comparison across other materials. Put plainly: if the artwork is photographic, lamination is not an upgrade, it is the only route to the image.

The film does three other useful things. It gives a water and stain resistant surface, so rain runs off and spilt coffee wipes away. It gives abrasion resistance, because the ink sits under the film. And it adds stiffness: an 80 gsm laminated bag stands on a shelf roughly the way 100 gsm plain does, corners stay square and gussets hold their shape, which is why most carriers in the laminated non-woven range are built this way. Note the limit on the water claim, though: the surface repels water, the bag does not contain it. Stitch perforations, handle joins and raw cut edges all admit it.

What lamination costs you

The obvious cost is money — extra material, an extra converting pass, cylinder engraving, setup waste. The less obvious ones cause the arguments.

Weight and bulk. Film adds mass and thickness, so cartons hold fewer bags and cubic volume rises. On airfreight or a tight container plan that shows up in landed cost, so ask for the carton count both ways.

Mixed construction at end of life. Fabric, film and adhesive are bonded and cannot be separated in a normal collection stream. Both layers are polypropylene, but a laminated bag is still a multi-layer article, and whether the recycling system in your destination market accepts it varies by country and often by council. Unlaminated fabric is a single-polymer construction and a far simpler conversation. Do not put a recycling symbol on artwork until the local position has been checked.

No breathability. The film is a vapour barrier. Warm bakery items, hot takeaway containers, fresh produce, damp swimwear and gym kit all release moisture, and inside a laminated bag it condenses on the film with nowhere to go.

Crease memory. BOPP holds a fold. Flat-packed and compressed bags arrive with visible crease lines through the print, worst across dark solids; they relax but never completely. If bags go straight onto a retail display, specify interleaving or roll packing.

Where unlaminated fabric still wins

Plain spunbond is not the budget compromise it is sometimes made out to be. It is the cheapest construction per bag and the lightest, which helps twice over on freight. It breathes, it has a softer textile hand-feel, it folds flat without creasing a print, and there is no film to bubble or lift, so inspection is simpler. A crisp one- or two-colour screen print on 80 gsm fabric does not read as cheap, it reads as deliberate.

For high-volume distribution — conference bags, supermarket carriers, charity and campaign work — unlaminated is usually the right call, and the d-cut style exists to make that economical. Breathable applications such as shoe and dust bags should never be laminated whatever the artwork wants. Between those poles sits the general non-woven shopping bag range, which is quoted both ways as standard.

Fabric weight and lamination interact

At 60–70 gsm the fabric is light and floppy, and laminating it produces a striking change in feel. Do not confuse that with strength: stiffness comes from the film, load capacity comes from fabric mass, seam construction and handle attachment. Film does not stop a handle tearing out.

80–100 gsm is the retail default, and 90 gsm laminated is about the most common boutique carrier specification there is. Above 120 gsm you are into gift and premium territory, usually matte laminated with rope or ribbon handles and a board insert in the base. Our fabric weight guide maps those bands onto load and bag style.

There is a nomenclature trap here that costs buyers money. The gsm you order normally describes the spunbond substrate alone; film is specified separately in microns and its weight is not included. Polypropylene has a density of about 0.905 g/cm3, so a 12 µm film contributes roughly 11 grams per square metre and an 18 µm film roughly 16, before adhesive. Some suppliers instead quote the laminated composite, meaning their “90 gsm laminated” bag may sit on a 75 gsm substrate. Two quotations with the same number can describe different bags. Ask in writing which convention applies.

A decision sequence that usually settles it

1. Photograph, soft gradient, or more than about four colours in the artwork? Laminate; there is no other route to that image.
2. Do the contents need to breathe? Do not laminate, whatever the artwork says. Change the artwork instead.
3. Carried in the rain, or holding anything that leaks? Lamination helps, within the limits above.
4. Mass give-away where unit cost dominates and the artwork is a logo? Unlaminated, d-cut or loop handle.
5. Retail carrier that has to look like the brand on a shelf? Laminated, commonly matte on 90–100 gsm with a reinforced base.
6. Run short enough that tooling is a large share of the total? Screen printing spreads better across it than gravure cylinders.
7. Customer policy on material construction? A single-polymer unlaminated bag is easier to defend.

What to inspect, and how

Lamination adds failure modes, so it adds inspection points. These are the ones worth writing into the order.

• Bond strength. A 180 degree peel on a cut strip should tear fibre from the fabric rather than release cleanly at the interface; clean separation means the adhesive has not keyed in. Add a thumb-rub at corners and handle folds, and hold retained samples in heat and humidity before re-checking for edge lift.
• Bubbles and tunnelling. Inspect under raking light, not flat overhead light. Entrapped bubbles are nearly invisible face-on and obvious at an angle, and show worst in dark solids.
• Colour. Assess against a signed production sample in a D65 light booth, never under warehouse lighting, and set a numerical tolerance in the order — a delta E of 2 or below is a common commercial limit for a brand colour. Matte and gloss will not measure the same from the same ink, so the reference must be the same finish as production.
• Handles and welds. Load the bag to its rated weight and lift repeatedly. On ultrasonically welded laminated bags, check the horn has not burned through the film: over-welding gives a glassy, brittle join that cracks in service. Heavier loads should be sewn with a box or cross stitch.

Add the geometry checks you would run on any bag — finished width × height × gusset against tolerance, print position relative to the fold, gusset symmetry — and an agreed sampling plan. AQL 2.5 major / 4.0 minor at general inspection level II under ISO 2859-1 is the usual default. Our quality and inspection page covers how these are handled on an order.

When we would tell you not to laminate

This is the part most supplier pages leave out, so we will be direct. If the bag is a give-away and the artwork is a logo, film is money the recipient never notices. If it carries anything warm or moist, lamination makes the product worse. If your buyer’s packaging policy favours single-material construction, a two-layer laminate with an adhesive interlayer is harder to argue.

And if budget is tight, think about where the money is better spent. The cost of laminating a light fabric would often buy 20 gsm more substrate instead, and a heavier plain bag survives more trips than a light laminated one. The environmental argument for a non-woven bag rests entirely on reuse, and reuse is a durability question — fabric mass, seams, handle attachment — not a surface question. If the bags will sit flat in storage for months before use, crease lines through a dark laminated print are a predictable complaint you can avoid.

What your specification should say

Most requotes are caused by an incomplete brief. A specification naming these fields will get you comparable numbers from any supplier, and it takes ten minutes to write.

• Substrate — spunbond polypropylene, stated gsm, and whether that figure is fabric alone or laminated composite.
• Lamination — laminated or not; if laminated, BOPP thickness in microns, gloss or matte, bonding method.
• Print — method, spot colours or four-colour process, Pantone references with the coated or uncoated suffix, coverage area, one side or both.
• Colour control — tolerance figure, and a signed physical sample rather than a screen proof as the approval reference.
• Bag style and size — width × height × side gusset in a stated order and unit, plus bottom gusset where relevant.
• Handles — type, length, width, attachment method, rated load.
• Construction — ultrasonic welded or sewn, edge finish, base board or reinforcement.
• Packing — individual polybag or not, count per inner, flat or roll packed, carton dimensions, gross weight, shipping marks.
• Inspection — sampling standard and AQL levels, plus required tests such as peel, handle pull and colour measurement.
• Claims — any wording to be printed, and the evidence you expect behind it.

Send that with your artwork and destination market through our quotation form and the reply can be specific rather than a range. If you are still weighing the two constructions, ask for both quoted side by side at the same quantity; seeing the gap settles it faster than any article can. We usually reply within one business day.

Frequently asked questions

Does lamination change the gsm of the bag?

The gsm figure on a quotation normally describes the spunbond fabric only. BOPP film is specified separately in microns and its weight is not included in that number. A 12 µm film contributes roughly 11 grams per square metre and an 18 µm film roughly 16, before adhesive. Ask in writing whether a stated gsm is the substrate alone or the finished laminate, because both conventions are in use.

Can you print a photograph on unlaminated non-woven fabric?

Not well. Screen printing onto a fibrous, slightly stretchy web cannot hold the fine halftone dots a photograph needs, so dots fill in and gradients break up. Photographic and four-colour process artwork is printed by rotogravure onto BOPP film, which is then laminated to the fabric. If the artwork is photographic, lamination is not a finish choice, it is the print process.

Are laminated non-woven bags waterproof?

The surface is water resistant rather than waterproof. Rain beads and runs off and spills wipe clean, but the bag is not a sealed vessel: stitch holes, handle joins and cut edges all admit water. For contents that must stay dry, specify a welded or lined construction instead of relying on the film.

Can laminated non-woven bags be recycled?

Both layers are polypropylene, but the fabric, the film and the adhesive between them cannot be separated in a normal collection stream, so whether a laminated bag is accepted depends on the system in the destination market. Unlaminated fabric is a single-polymer construction and is a simpler case. Check the local position before any recycling symbol is printed on the bag.

Should I choose gloss or matte lamination?

Gloss gives deeper apparent colour saturation and denser blacks, and it wipes clean. Matte reads flatter and more restrained, but its surface microstructure holds skin oils, so fingerprints and scuff marks show, especially across large dark solids. If the design is dark and matte, handle a physical sample before approving it.

Most sourcing pages on this subject read like a menu: a list of green-sounding materials, a row of certification logos, and an invitation to enquire. That is not much help when a retailer’s compliance team asks you to substantiate the word printed on your packaging.

This guide takes the opposite approach. For each of the main lower-impact bag materials it sets out what the material physically is, what it does well, where it costs you performance, and — the part that usually gets skipped — exactly which document you need in your file before a claim about it is safe to publish.

Three things buyers keep mixing up

Almost every argument about green packaging comes from collapsing three separate questions into one.

Composition is what the bag is made from: recycled polyester, virgin polypropylene, cotton, paper pulp, a starch-based film. This is a factual question and it is answered by a specification and a certificate of analysis.

End of life is what happens to the bag afterwards: kerbside recycling, industrial composting, incineration, landfill. This is not a property of the material alone. It depends entirely on the collection infrastructure in the market where the bag is thrown away, which is why the same bag can be genuinely recyclable in one country and not in another.

Substantiation is the paperwork that connects the first two to your specific order. A certificate held by a mill somewhere upstream is not the same as evidence that your goods contain the certified material. This distinction is where most greenwashing complaints actually originate, and it is the one we spend the most time on with buyers.

Recycled PET (RPET)

RPET shopping bags are woven or non-woven from polyester fibre spun out of post-consumer PET, most commonly beverage bottles. Mechanically the fabric behaves like conventional polyester: it is strong for its weight, it folds down small, it takes a printed image well and it washes.

What to specify. The recycled percentage, whether it is post-consumer or post-industrial, and the fabric weight. Post-consumer is the claim buyers care about; post-industrial recycled content is factory scrap and is much less meaningful to a compliance reviewer.

The document. The Global Recycled Standard (GRS) or the Recycled Claim Standard (RCS), both administered by Textile Exchange and issued by accredited certification bodies. The important nuance is that there are two kinds of document. A scope certificate says a company was certified for certain processes during a certain period. A transaction certificate ties a specific shipment of goods to that certification. Only the second one connects the claim to your order.

Where it costs you. Recycled polyester generally carries a premium over virgin, the colour consistency of undyed recycled fibre can vary between lots, and very light shades are harder to achieve cleanly. None of these are dealbreakers, but they belong in the quotation conversation rather than in a surprise later.

Cotton canvas: organic, recycled and conventional

Cotton canvas totes are the material buyers reach for when the bag is meant to be kept rather than used once. The hand-feel is genuinely different from synthetics and the bag survives years of use, which is the strongest argument in its favour.

It is worth being clear-eyed about the trade-off. Cotton is agriculturally intensive, and the life-cycle studies that compare a cotton tote with a light plastic bag usually conclude that the cotton bag has to be reused a great many times before it comes out ahead. That is an argument for durability and for designing a bag people actually want to keep — not an argument for calling cotton automatically better.

The documents. GOTS covers organic fibre content together with processing, chemical and social criteria; the Organic Content Standard (OCS) covers organic fibre content only. Recycled cotton falls under GRS or RCS as above. All of these are issued to the certified mill or processor, not to a bag maker, and again you want the transaction certificate for your goods.

Ink matters here. Pairing certified cotton with plastisol ink is a common own goal, because plastisol is a PVC-based system and it undermines the story the fabric is telling. Water-based and discharge inks are the usual alternatives, with a softer hand-feel and slightly different colour behaviour on dark fabric.

Kraft and art paper

Kraft paper bags have the widest genuine recyclability of anything discussed here, simply because paper collection is nearly universal and paper mills want the fibre. That is a real, defensible advantage.

The document. FSC or PEFC chain of custody. Both trace fibre back through the supply chain to a managed forest source. As with textiles, the certificate belongs to the mill and the converter; a claim on your bag needs the chain to be unbroken all the way to the printer, which is a stricter requirement than most buyers expect.

What breaks it. Lamination. A gloss or matte film laminated over a paper bag makes it look premium and makes it much harder to recycle, because the plastic layer has to be separated from the fibre. Foil stamping, heavy PVC-based coatings and plastic-reinforced handles do the same. If recyclability is the point of choosing paper, the finishing specification has to respect that.

Plant-starch film (PBAT and PLA)

Plant-starch mailing bags are made from a blend of PBAT, a flexible co-polyester, and PLA derived from corn starch. They keep the self-seal convenience and full-surface print area of a conventional poly mailer.

What the standards actually say. EN 13432 in Europe and ASTM D6400 in North America describe behaviour under industrial composting conditions: elevated temperature, controlled humidity, active microbial load, over a defined period. They say nothing about what happens in a garden compost heap, in soil, or in the sea. Home compostability is a separate certification with a different test protocol. Conflating the two is one of the most common substantiation failures in this category.

What it costs you. Starch-based film is typically less tear-resistant than polyethylene at the same thickness, which often means specifying a heavier gauge and giving back some of the material saving. It also has a shorter shelf life, so ordering a year of stock in one go is a poor idea. If your bags travel through humid warehousing, say so at the enquiry stage.

What to avoid. Oxo-degradable film, which is conventional plastic with an additive that accelerates fragmentation. It does not meet composting standards, it is restricted in the European Union under the Single-Use Plastics Directive, and it is not a material we would recommend specifying.

Polypropylene non-woven: the reuse argument

Non-woven PP bags deserve an honest paragraph, because they are the highest-volume product in this category and the claims made about them are frequently wrong.

Standard PP non-woven is not compostable and does not biodegrade in any meaningful timeframe. Its environmental case rests on one thing only: it replaces a large number of single-use bags, provided it is actually reused. That case is real, but it is a durability argument, and durability is a specification question — fabric weight, handle attachment method, base construction. Our guide to non-woven fabric weight covers how that translates into a spec.

The material is PP number 5 and therefore technically recyclable, but practical recyclability depends on local collection, and laminated non-woven generally is not recyclable at all because the BOPP film cannot be separated from the substrate in a normal stream. If a recyclability symbol is going on the bag, check the destination market first.

The certificates, and who actually issues them

None of the schemes below are issued by bag factories. They are issued by accredited certification bodies to the specific companies in the chain that were audited.

• GRS / RCS — recycled content in textiles, administered by Textile Exchange. GRS adds social, environmental and chemical criteria on top of RCS.
• GOTS / OCS — organic fibre. GOTS also covers processing and social criteria; OCS covers content only.
• FSC / PEFC — forest source and chain of custody for paper and pulp.
• EN 13432 / ASTM D6400 — industrial compostability of a specific film, evidenced by a test report or a scheme certificate such as those issued by TUV Austria or DIN CERTCO.
• REACH / Proposition 65 — chemical restrictions on inks, coatings and hardware, evidenced by a laboratory test report on the finished item rather than by a certificate.
• BSCI / Sedex SMETA — social compliance audits of a named facility. These are audit reports about labour and working conditions, not product claims, and they cannot be used to substantiate anything about the material.

How to check a certificate in ten minutes

Buyers are handed PDFs constantly and most never verify them. Four checks catch nearly everything.

Check the holder. Whose name is on it? If the certificate names a fabric mill and your supplier is a bag converter, the certificate does not by itself cover your goods.

Check the scope. Certificates list the processes and product categories they cover. A certificate covering woven fabric does not cover a printed and sewn bag.

Check the dates. Scope certificates expire, usually annually. A certificate that lapsed before your production window is not evidence for your order.

Check the register. GOTS, GRS and FSC all publish searchable public databases of valid certificates and licence numbers. If the number on the PDF is not in the register, stop and ask questions.

The regulators are catching up

Vague environmental language is no longer a low-risk marketing choice. The UK Competition and Markets Authority publishes a Green Claims Code and has taken action against consumer brands over unsubstantiated packaging language. The European Union’s Empowering Consumers Directive restricts generic environmental claims that are not backed by recognised evidence. In the United States, the Federal Trade Commission’s Green Guides set out what terms such as recyclable and degradable may be used to mean.

The practical consequence for a packaging buyer is simple: a specific, documented claim is safer than a broad one. “Made with 80% post-consumer recycled PET, GRS transaction certificate available” is defensible. A leaf icon next to the word “eco” is not.

Where we stand

We think it is worth being direct about this, because a lot of supplier pages are not.

We do not hold GOTS, GRS, FSC, BSCI or Sedex certification in our own name, and we do not present those schemes as though we did. What we do is source from mills and converters that hold the relevant certification for the material your project requires, arrange it per order, and pass the certificate and transaction documentation to you. We confirm the certificate number and its scope in writing before the word “certified” appears anywhere on your artwork. If a claim cannot be evidenced for your specific order, we will tell you and we will not print it.

Our production base is an SGS-verified facility in Wenzhou, which is a supplier verification that can be checked independently. Our quality and claims policy sets out in more detail which words we will and will not put on a bag, and what evidence each one requires.

What to send us

If a material or environmental requirement is part of your brief, four pieces of information let us answer it properly rather than generically: the destination market and any retailer or platform policy you have to satisfy, the exact wording you intend to put on the bag or the listing, whether you need the certificate itself or only the material, and who your compliance reviewer is going to be. That last one matters more than people expect, because a claim that satisfies a marketing team and a claim that satisfies a legal team are rarely the same sentence.

Frequently asked questions

Is a non-woven polypropylene bag recyclable?

The material is polypropylene, technically recyclable as PP number 5. Whether it is recyclable in practice depends on the collection system in your market, and laminated bags usually are not, because the BOPP film and the PP substrate cannot be separated in a normal recycling stream. Check the local system before printing a recyclability symbol.

What is the difference between GRS and RCS?

Both cover recycled content. RCS verifies the recycled input and its chain of custody. GRS does the same and adds social, environmental and chemical criteria at the processing stages. GRS is the stricter of the two and the one most large retailers ask for.

Does a certificate on the fabric cover the finished bag?

No. A scope certificate proves that a named company was certified for named processes during a named period. To connect that certificate to your specific goods you need a transaction certificate covering your shipment. Ask for both.

Can a bag be certified compostable?

Film can be produced against EN 13432 or ASTM D6400 requirements, which describe industrial composting conditions rather than home composting or open environments. Home composting is a separate certification with its own test protocol. Certification is arranged per order and the certificate number is confirmed in writing before anything is printed on the bag.

What is oxo-degradable plastic and should I use it?

Oxo-degradable plastic contains an additive that makes conventional plastic fragment faster. It does not biodegrade in the way a composting standard defines. It is restricted in the European Union under the Single-Use Plastics Directive and it is not a material we recommend specifying.

A brand team approves a tote sample, signs off the artwork, and then finds the bags that arrive are not the ones they approved: the navy has drifted, the logo sits lower, and the sewn-in label carries a fibre claim nobody can document. Usually nothing dramatic happened at the factory. The specification never existed in the form a factory can build from, so a dozen small decisions were made by somebody else.

Private label bag work is a definition problem more than a manufacturing one. What the bag is, who owns it, what may be printed on it and what counts as acceptable is where programmes hold together or unravel. Here is what to define, what to sample, what to contract — and when private label is the wrong route.

Four labels, four different deals

Private label means an existing product is sold under your brand: construction, pattern and often material stay the supplier’s, and you add the mark. White label is the same without exclusivity. OEM means you bring the specification, artwork and sometimes a graded pattern, and the factory builds to it. ODM means the supplier’s own team developed the product and sells you the right to carry it. Each arrangement splits three things differently: who owns the design, who carries development risk, and who owns the tooling.

Under OEM the design is yours to take elsewhere, but a pattern fault is yours too; under ODM the risk sits with the developer, while the construction stays theirs and is rarely exclusive unless bought. Suppliers in China use all four words interchangeably, since “OEM/ODM” has become one phrase meaning “we accept customisation”. Define the substance in the order document: who owns the artwork, graded pattern and technical drawing, who owns the screens, gravure cylinders and cutting dies, whether the construction may be offered to other buyers, and who pays when a developed sample fails. Our page on custom and OEM work divides those responsibilities.

Decide what the bag has to do before you decide what it is

The specification follows the role the bag plays, not the mood board. As a packaging carrier it is seen briefly and often photographed, so the job is print fidelity and structure: colour held to the brand standard, square corners, a handle that survives being filled — pointing at paper carriers with a coated or laminated face. As a retail item the bag is the product, inspected for stitch density, hardware, lining and fibre content, and it needs a barcode and composition label: usually cotton canvas at a stated ounce weight, sewn rather than welded.

As a gift item, hand-feel and individual packing outweigh unit cost; as a give-away the reverse holds, and a light construction from the non-woven bag range with a one- or two-colour print is the answer. Size needs the same discipline: work from what the bag must hold, in the orientation it will hold it, then add ease. Fix the order of dimensions and the unit, say whether height runs to the top edge or over the handle, and give the gusset explicitly — our guide to sizing and gussets covers the datums behind most disputes.

The brand asset pack that makes a real quotation possible

More sampling rounds come from an incomplete asset pack than from disagreement. Assemble this once and issue it as a set.

• Vector artwork in AI, EPS or PDF, fonts converted to outlines, effects flattened. An upscaled PNG will be redrawn by someone who has never seen your guidelines.
• Pantone references with the suffix. Coated and uncoated versions of one number are different targets, and on textiles TCX is the relevant system. Name the reference and the substrate together, and expect a close match rather than identity across substrates.
• Minimum legible size and line weight. Fine lines and small reversed type fill in as ink wicks along the fibres, so fix the smallest size at which the mark still reads and supply a simplified single-colour version.
• Clear space referenced to construction, not to the logo box. Seams, gusset folds, handle roots and the base crease sit in fixed positions, and a mark across a fold will crack, so give a keep-out zone from each edge and fold line.
• Regulatory and language content. Origin marking, fibre or material composition, importer details, care symbols, translated text, and recycling marks only once the evidence question below is settled.

The print process constrains the artwork, so choose it early: screen, gravure, transfer and digital routes differ in what they hold in gradients and registration. Our note on print methods and what drives their cost matches artwork to process.

Sampling in stages: blank, printed, signed

Each stage answers one question. The blank sample comes first — correct material and construction, no print — settling dimensions, gusset behaviour, handle drop, seam positions and base reinforcement. It is cheap because no tooling exists yet, so be fussy here. The printed sample follows, made from bulk material with production tooling, and answers colour, registration, print position relative to the fold and finish. The signed sample is a contractual object: two identical units, dated, referenced to the specification version, signed and sealed, one held by each side as the standard for later batches.

Skipping the blank stage is a false economy: you assess geometry and colour at once, so a fault in one gets blamed on the other, and a dimensional change after screens or cylinders exist means paying for tooling twice. Colour needs the same rigour: judge against the signed sample in a standard light booth, D65 or D50 as agreed, never on a monitor, and record the tolerance as a number. A delta E of 2 or below is a common commercial limit on a smooth substrate, wider on textiles. Without a sealed sample, “the colour is wrong” is an opinion.

Trader, factory or integrator: know which one you are talking to

A trading company offers breadth and low friction, often enough for a standard article; on a specified programme the risk is that nobody in the chain controls the line. A single factory gives process depth but is narrow — a non-woven welding line will not sew heavy canvas — so a brand needing carriers, totes and mailers ends up with several suppliers and no owner of the brand standard. An integrator coordinating specialist workshops under one specification solves that, but is only as good as its vetting and its willingness to say where production happens.

Three questions separate them. A process question only a production person can answer: what mesh count for the finest line in your artwork, or what corona treatment decay means for ink adhesion on stored fabric. A failure question: what happens when a batch lands outside tolerance, who reworks it and who pays. An accountability question: who signs off a deviation and how it reaches you. Our article on how to vet a bag manufacturer works through those checks.

Intellectual property, tooling and confidentiality

An NDA defines what is confidential, names the entity holding your files, sets governing law and forum, and gives you a basis if artwork leaks. It is weak as a practical barrier: it binds only the entity that signed it, not a third workshop that never saw it. Commercial structure protects a design better. Own the tooling and list it item by item — screens, gravure cylinders, cutting dies, embossing plates, moulded hardware — recording who paid, who owns, where it is stored and what happens if the relationship ends. A tooling charge transfers no title unless the contract says so.

Hold the graded pattern and technical drawing as your own documents, and register your marks where you sell and in China, since a local dispute turns on local rights. If a construction was developed for you, the contract should say it will not be offered to other buyers, with a stated duration and scope, distinguishing your artwork from a generic construction that may not be exclusive. Photograph rights run both ways: require in writing that your branded samples stay off the supplier’s listings and stand. That is our own policy in reverse — we do not publish customer logos, samples or artwork without written permission.

Claims and certificates: the easiest thing to get wrong

The riskiest thing printed on a private-label bag is usually a sentence, not an image. Recycled content, organic fibre, responsible forestry and chemical screening are scheme claims, and every scheme works the same way: the certificate is held by the mill or the converter, not by a trading partner, and it covers specific material within stated validity dates. A supplier holding a scope certificate is not the same as your order being covered; the transaction-level document tying your goods to the scheme is arranged per order.

So the certificate number, scope and validity must be confirmed in writing before wording goes onto artwork — the one element you cannot quietly amend afterwards. Where a claim cannot be evidenced, do not print a softer version of it: unqualified environmental wording attracts regulatory attention in the EU and the UK. Recycling marks add a step: a resin identification code describes the polymer without promising anyone collects it, and acceptance varies by country. Our guide to recycled materials and what a certificate actually covers takes the schemes one at a time.

Quality, packing and labelling belong in the order document

Agree the sampling plan by name: ISO 2859-1, general inspection level II, AQL 2.5 major and 4.0 minor is the usual default, applied at a during-production check and a final random inspection. Then define what a defect is for this bag, in three grades. Critical: anything unsafe or contaminated, or a handle detaching below its rated load. Major: colour outside the agreed delta E against the signed sample, misregistration beyond the stated millimetre allowance, a dimension out of tolerance, broken stitching, delamination, a missing label. Minor: loose thread ends and faint handling marks within limits.

Attach a remedy to each grade — sort, rework, discount or reject — and state who bears the cost and how an exception is escalated and recorded on the order confirmation. Our quality and inspection page describes how these gates run.

Packing is a brand decision disguised as a logistics one: whether each bag needs an individual polybag and whether that bag is printed, the count per inner, flat or roll packing to avoid crease lines through dark print, carton dimensions and shipping marks. Barcodes belong to you: EAN and UPC numbers are licensed to the brand owner through GS1, so the supplier prints what you supply and verifies the symbol on the actual substrate. Finish with destination requirements: origin marking, composition and care labelling, importer identification and language rules.

First order and repeat order are different projects

A first order pays for work that never repeats: freezing the specification, the sampling rounds, tooling, colour approval, label artwork and the first inspection cycle, spread across the units ordered. A repeat order reuses the signed sample, the tooling, the colour standard and the inspection plan, so fewer variables remain open and the risk of rework falls because the physical reference already exists — structural reasons, not a favour. Repeat orders fail in their own way: fabric arrives from a different mill lot, an ink batch is mixed afresh, a workshop substitutes a webbing that looks equivalent, and nobody flags it because the order said “same as last time”. Never write that. Reference the specification version and signed sample on every order, and state that substitutions need written approval.

Managing the programme once it scales

Version control. Every specification change takes a version number and an effective date, superseded versions are marked, and each purchase order names the version it was built against. Keep a change log of what changed and who approved it; that habit prevents most disputes about what was agreed.

Batch colour. Colour drifts between lots because pigment batches, fabric lots and substrate whiteness vary. Keep the sealed master out of daylight, use working copies on the floor, measure rather than eyeball, and where colour is critical ask for a season’s fabric to be blocked from one mill lot.

Buffering and fallbacks. Decide in advance where the buffer sits: reserved fabric from an approved lot, finished stock held at destination for launch periods, and a qualified alternative material that may be substituted with your written approval if a lot fails inspection. Set the levels against your sales pattern and replenishment cycle.

When private label is the wrong answer

Sometimes the honest advice is not yet, and it is better said before tooling exists. If your quantity is small relative to the development work, setup dominates the cost and you pay a premium for a bag nobody has asked for. If the design is still moving, every revision reopens sampling and possibly tooling, so freeze it first. If demand is unproven, a bespoke bag is an expensive test: a standard style from the non-woven shopping bag range with a simple print answers the market question at a fraction of the committed cost. And if the programme rests on a certified claim you cannot yet evidence, wait for the documents.

When it does make sense, our approach is straightforward. We act as a sourcing partner rather than a catalogue: production runs through an SGS-verified facility in Wenzhou, specification and tooling ownership are agreed in writing before sampling begins, colour is controlled against a sealed signed sample, and any claim you want printed is checked against a certificate covering your order. Send your artwork, quantity, destination market and material requirement through our quotation form and the reply will be specification-based, with sampling options and a clear answer on what can be evidenced. We usually reply within one business day.

Frequently asked questions

What is the difference between private label, white label, OEM and ODM?

Private label means an existing product sold under your brand. White label is the same with no exclusivity. OEM means the factory builds to your specification, pattern and artwork. ODM means the supplier developed the design and sells you the right to carry it. The terms are used loosely, so define ownership of artwork, pattern and tooling in the contract.

Who owns the printing screens, gravure cylinders and cutting dies?

Whoever the contract says. Paying a tooling charge does not by itself transfer ownership. List each item — screens, cylinders, cutting dies, embossing plates, moulded parts — and state who owns it, where it is stored and what happens if the relationship ends. Do the same for the graded pattern.

Why do we need a blank sample before a printed one?

A blank sample settles construction, dimensions, gusset, handle length and stitching before any tooling is cut. Going straight to a printed sample means judging geometry and colour at once, and a dimensional change after screens or cylinders exist means re-tooling. Blank first, printed second, then a signed reference held by both sides.

Can you print a recycled or certified claim on our bags?

Only where a certificate covers the actual order. Certification is held by the mill or converter and arranged per order, so the certificate number, scope and validity dates must be confirmed in writing before the wording goes onto artwork. A general supplier statement is not evidence.

When is private label the wrong choice for a small brand?

When the quantity is too small to spread specification, sampling and tooling work across the units ordered, when the design is still changing, or when demand has not been tested. A standard style with a simple print, or none at all, reaches the market with less committed cost.

For any e-commerce or DTC brand shipping apparel and soft goods, the poly mailer is the cheapest, lightest and most brandable way to get a parcel to the door. Here is how to specify custom poly mailers that protect your product, keep postage low and turn every delivery into a brand moment.

Poly mailer vs bubble mailer vs courier bag

A flat poly mailer is best for non-fragile soft goods — clothing, textiles, accessories. A courier bag with a document pocket adds a sleeve for the packing list. For anything that can dent or scratch, a cushioned bubble mailer adds an air-bubble lining.

Choosing the right thickness (micron)

Poly mailer thickness is measured in microns (µm) or mil. Lightweight mailers run around 50–60 µm for small, light items; standard mailers are 60–80 µm; and heavy-duty co-extruded mailers reach 90–120 µm for bulky or multi-item orders. Co-extruded (multi-layer) film is opaque and much harder to tear than single-layer film.

Sizing your mailers

Measure your most common product flat, add 2–3 cm on each side for easy packing, and leave room for the self-seal lip. Most brands settle on two or three sizes to cover 90% of orders. Custom dimensions are made-to-order, so you are not forced into stock sizes that waste dimensional weight.

Branding and finish options

• Full-colour print inside and out — logos, patterns, unboxing messages
• Matte or gloss film, or metallic finishes for a premium look
• Double self-seal strip for easy returns without tape
• Tear-strip opening for a clean customer experience

Material options, and what you can actually claim

There are two common alternatives to conventional polyethylene film. Plant-starch mailers in a PBAT and PLA blend keep the self-seal convenience of a poly mailer and can be produced against EN 13432 or ASTM D6400 requirements when a project calls for it; those standards describe industrial composting conditions rather than home composting, certification is arranged per order, and the certificate number is confirmed in writing before anything goes on the artwork. Recycled-content film is the other route, evidenced by a certificate of analysis from the resin supplier and, where a buyer’s programme requires it, a third-party laboratory report on the finished film. Both carry trade-offs worth knowing before you commit: starch-based film is less tear-resistant at the same gauge and has a shorter shelf life, so it is not a material to stockpile. Our guide to material claims and the documents behind them goes through this in detail.

Minimums, samples and scheduling

There is no single site-wide minimum for printed mailers. It moves with the film gauge, the number of print colours, whether you need more than one size in the same run, and whether the film is conventional, recycled-content or plant-starch. The same applies to the schedule: sampling, bulk production and transit are quoted for your specific order and set out with a dated timeline in the quotation, then reconfirmed on the order confirmation. Send us your product dimensions, your monthly volume and your artwork, and we will recommend the size, thickness and finish, then price it against a written specification rather than a generic range.

Two quotations arrive for the same custom non-woven bag, both marked 90 gsm, same size, one clearly cheaper. When the samples land, the cheaper bag feels like a leaflet with handles, and neither document was false. gsm alone does not describe a fabric closely enough to compare.

Weight sets the floor on cost, predicts less than buyers assume, and is the line most often quietly shaved between quotation and shipment.

What gsm measures — and what it does not

gsm is grams per square metre: the mass of one square metre of fabric, an areal density rather than a thickness, a strength or a grade. ISO 9073-1 and ASTM D3776 weigh a conditioned specimen of known area and scale it up — the whole definition, and the trap, because two fabrics can weigh the same and behave nothing alike.

Filament fineness is one reason: finer filaments give more filaments per gram, better cover and higher tensile at the same weight. Bonding is another, engraved calender rollers fusing filaments where their raised points touch, so a large bonded area gives a stiff, papery cloth with poor tear resistance and small widely spaced dots a soft, drapey one — see how the fabric and the bag are made.

The third reason costs money: polypropylene has a density of about 0.905 g/cm3 and calcium carbonate filler around 2.7, so a filled fabric reaches nominal weight with less polymer doing structural work. A heavily filled 90 gsm can be weaker and more brittle than a clean 75 gsm while weighing exactly what the datasheet claims, so gsm belongs beside tensile values, not instead of them.

How to check gsm yourself, properly

Cut 10 cm × 10 cm with a template and blade — 100 cm2 — weigh it on a balance reading to 0.01 g and multiply the grams by 100: a 0.82 g specimen is 82 gsm. A square cut a millimetre generous on two sides reads 2% light, and an 80 gsm specimen weighs only 0.8 g, so cut ten, stack them and divide.

One specimen is not a measurement. Areal density varies across the web and drifts along the roll, and edges are least representative. Take five or more specimens from several bags and cartons, avoid print, hems, welds and handle overlaps, and report the mean and the spread: 90 with a range of 12 is a different purchase from 88 with a range of 3.

Humidity matters less than expected, because polypropylene is hydrophobic; what takes up water is the filler and finishes, plus condensation on samples from a cold container. Labs condition at 23 degrees Celsius and 50% relative humidity under ISO 139; in an office, unwrap the sample for a few hours and weigh control and production on one balance in one session. Better still, weigh specimens from the sealed signed sample and the shipment together, so calibration and template tolerance drop out.

Why gsm does not predict thickness, opacity or strength

Thickness. The web is compressible, so calliper needs a stated pressure, 0.5 kPa under ISO 9073-2, and a lightly bonded 70 gsm can measure thicker than a hard-calendered 90 gsm while testing weaker.

Opacity. Hiding power is optical, driven by fibre surfaces and pigment: a navy 60 gsm conceals contents better than a white 90 gsm, so pigment beats mass where the brief is “not see-through”.

Tensile. Results under ISO 9073-3 rise sub-linearly and are direction-dependent, machine direction typically one and a half to two and a half times cross direction, which makes panel orientation on the layout a real decision.

Tear and bursting. Here it inverts: bursting under ISO 13938-1 and tear under ISO 9073-4 need filaments free to share load, so as bonded area rises tensile improves while tear falls. And bags rarely fail mid-panel, but at the handle root, base seam or crease.

The four working weight bands

Mills run standard weights, and asking for 85 gsm where the line runs 80 and 90 can cost more than the next step up.

40–60 gsm — handouts, inner bags, dust covers

Light, soft, translucent and cheap, carrying a couple of kilograms of flat contents before the handle root gives way. Good for handouts, garment carriers, dust bags and single-piece styles such as d-cut and vest-handle bags, since a wide gusset in 50 gsm collapses. Print one or two bold spot colours: ink ghosts through and small type loses its edges. It reads as disposable — honest for a handout, wrong once the bag must be reused.

70–90 gsm — the working default

Most volume sits here, 80 gsm being the reference for supermarket carriers and conference bags: a normal grocery load and repeated trips, provided the handle root is reinforced. Most of the reusable shopping bag range is quoted in this band, and screen printing behaves predictably at four to six spot colours. Ten more gsm buys less perceived quality than lamination or a better handle. Wrong choice when the bag must stand square unsupported.

100–120 gsm — retail carriers and gift bags

Structured, stiff enough to stand up empty, and where a customer’s hand registers “quality”: 90 to 110 gsm is the most noticeable jump in perceived value. Home of boutique carriers, box bags and rope handles, usually laminated. The limit shifts onto handle attachment and base, so a board insert and reinforced root become normal, and load-bearing seams are better sewn. Wrong for a mass give-away, or contents that must breathe.

130–160 gsm and above — heavy duty and near-textile

Stiff, costly and bulky to ship. Some fabrics sold in this range are needle-punched or stitch-bonded rather than spunbond, which changes surface and print behaviour, so ask what the construction is. Sewn seams, webbing handles and a rigid base insert are normal, and the fabric supports tool bags and sample cases. The caveat is appearance: an 8 oz canvas tote is roughly 270 gsm of woven cotton and looks like it, so if the brief is hand-feel rather than load, price canvas too.

What gsm really does to unit cost

Fabric cost is close to proportional to weight: 80 to 100 gsm is 25% more polymer over the same layout. Unit price, though, is fabric plus costs that barely move with weight. Cutting waste follows bag geometry; printing follows colour count and run length, so screens and setup cost the same at 70 or at 120; forming labour per bag is roughly constant, rising at both ends since light fabric registers badly and heavy fabric welds slowly.

Freight is the forgotten line: these are low-density goods, charged on volumetric weight by air and constrained by cubic metres at sea, so thicker fabric means fewer bags per carton. Ask for carton count, dimensions and total volume at both weights, not only the unit price.

So the marginal return falls away quickly. From 60 to 80 gsm you buy function; from 90 to 110 you buy perception, rational for a retail carrier; from 120 to 140 most recipients cannot tell without both bags in their hands. Before approving the last increment, price a reinforced handle root, a base board or lamination instead.

Lamination changes the gsm arithmetic

This is the most expensive misunderstanding in the category. The gsm on a quotation normally describes the spunbond substrate alone; BOPP film is specified separately, in microns, and is not in that number. A 12 µm film contributes roughly 11 gsm and an 18 µm film roughly 16. Some suppliers quote the finished laminate, so a bag sold as “90 gsm laminated” may sit on a 75 gsm substrate. Ask in writing which convention applies.

Film also adds stiffness out of all proportion to its mass, a continuous, biaxially oriented layer sitting where bending stress is greatest. A laminated 80 gsm bag stands on a shelf roughly as a plain 100 gsm one does, so if you are reaching for weight because the bag looks unimpressive empty, lamination is the cheaper lever. Much of the laminated non-woven range uses lighter substrate for that reason.

What film does not add is load capacity, since handle tear-out and seam failure are unaffected. Hence an order of judgement: for stiffness, appearance, water resistance or print quality, consider lamination before weight; for load or tearing in service, weight and construction are the answer; if the contents must breathe, lamination is off the table and gsm is your only lever. Our comparison of laminated against unlaminated construction covers the rest.

Joining method and gsm are coupled

Ultrasonic welding fuses the fabric to itself with vibration and pressure, and the process window — amplitude, pressure, dwell, anvil pattern — is set against fabric mass. It narrows sharply at low weight: below about 60 gsm, too little energy and the seam peels, too much and the horn burns through or leaves a brittle join that cracks the first time the bag is folded. Heavy fabric needs more energy per unit length, so above roughly 120–130 gsm many converters move load-bearing seams to stitching; our note on welding against stitching sets out how to choose.

The handle root is the highest-stress point in any bag, and its reinforcement must rise with the fabric, because a heavier bag invites people to put more in it. A folded patch, a doubled hem or a box stitch through the root costs less than 20 gsm across the bag and does more for survival.

What gsm does to print

On light fabric, screen ink ghosts through to the reverse, wet ink wicks along filaments so fine lines gain weight, and the web distorts under squeegee pressure. Heavier fabric is flatter and more stable, so edges are crisper and light inks cover better. Two things are weight-independent: photographic and four-colour work is printed by rotogravure onto film and then laminated, because no screen print holds a smooth gradient on fabric; and printability depends on corona treatment, which decays in storage, so old stock prints badly however heavy it is.

Under-weight fabric, tolerances and the clauses that prevent it

Quoting 90 gsm and shipping 75 is a long-established way to hit a price target: the blunt version substitutes a lighter roll and hopes nobody cuts a specimen; the subtler one delivers nominal weight with filler, so the balance reads correctly and the tensile does not.

So write the number properly. State nominal gsm with a tolerance — mills generally work to about plus or minus 5%, and 3% is achievable on a well-controlled line — name the test method, ISO 9073-1 or ASTM D3776, the specimen area and count, and that the mean governs, not any single reading. Say whether a laminated weight is substrate or composite, and name the reference: a signed, dated counter-sample plus the mill’s roll certificate of areal density per lot.

AQL 2.5 major / 4.0 minor at general inspection level II under ISO 2859-1 is the usual default, and right for visual defects and dimensions, but it is attribute sampling and areal density is a variable. Specify it separately: destructive specimens per lot from different cartons, tested for gsm, tensile in both directions and handle pull, with pass criteria beside the AQL clause.

A specification naming these fields will get comparable numbers from any supplier:

• Substrate — spunbond polypropylene, nominal gsm, tolerance, test method, filler limits.
• Whether that gsm is substrate or laminated composite — in words, not implied.
• Mechanical requirements — tensile in both directions, rated load for the bag.
• Lamination — film type, thickness in microns, gloss or matte.
• Print — method, colour count, Pantone references with coated or uncoated suffix.
• Size — width × height × gusset, with the measurement conventions agreed.
• Handles — type, length, width, attachment, root reinforcement.
• Construction — welded or sewn, seam allowance, base insert.
• Packing — count per inner, carton dimensions, total volume.
• Inspection — sampling standard, AQL levels, destructive test plan, sample number.

Working back from the use case to a weight

Derive the number from the job rather than from a figure someone quoted at you.

1. Load. Weigh the heaviest realistic contents, not the intended contents; that sets the floor for fabric mass and dictates handle and base construction.
2. Reuse. A handout has no durability requirement; a bag meant for repeated trips needs mass and a reinforced root.
3. Print complexity. Photographic or four-colour artwork forces a laminated construction, so settle the artwork first.
4. Lamination. Decide it before final gsm, since film substitutes for roughly 20 gsm of stiffness, and rule it out if the contents must breathe.
5. Geometry. A tall panel with a wide gusset needs more stiffness than a flat d-cut of the same capacity.
6. Brand perception. Must the bag stand square and empty in front of a customer? That is stiffness: 100 gsm and above, or lamination.
7. Budget. Check the freight consequence, then ask whether the last increment beats the same money spent on the root or the film.

When we would tell you not to go heavier

We will be direct about where extra weight is wasted money. If the bag is a genuine single-use handout, mass is material the recipient never notices. If the contents must breathe, you cannot laminate and a denser fabric makes it worse. If bags are failing at handles or seams, weight will not help: the failure is at the join.

Where the requirement is “not see-through”, pigment is cheaper than mass; where it is “stands up on the shelf”, lamination or a base board is cheaper than 20 gsm. And if you are going heavier because a previous order arrived under-weight, that is the wrong fix — put a tolerance, a test method and an incoming check in the order instead.

If you would rather not guess, tell us the load, the contents, the artwork and the destination market through our quotation form, and ask for two weights quoted side by side with carton counts and volumes for both. We usually reply within one business day.

Frequently asked questions

How can I check the gsm of a non-woven bag myself?

Cut a 10 cm × 10 cm specimen, which is 100 cm2, weigh it and multiply the grams by 100. Stack ten specimens and divide to suppress cutting and balance error, take them from several bags and cartons, and avoid print, welds and hems.

Why do two bags with the same gsm feel completely different?

Because gsm is only mass per square metre. Filament fineness, the calender bond pattern and calcium carbonate filler all change hand-feel, stiffness and strength at identical weight, so a heavily filled 90 gsm fabric can be weaker than a clean 75 gsm one.

Does lamination count towards the gsm figure?

Normally not. The quoted gsm is the spunbond substrate, while BOPP film is specified separately in microns, and 12 µm film adds roughly 11 gsm. A bag sold as 90 gsm laminated may sit on a 75 gsm substrate, so ask which convention applies.

What gsm should I use for reusable grocery bags?

The 70–90 gsm band, usually 80, takes a normal grocery load and repeated trips. The deciding factor is rarely the last ten gsm: handle root reinforcement, the base seam and the gusset govern whether the bag survives.

What gsm tolerance should my specification state?

Nominal weight plus or minus 5% is normal mill practice, and 3% is achievable on a well-controlled line. Name the test method, specimen area and count, state that the mean governs, and add a destructive test plan, since attribute sampling does not cover a variable like areal density.

Most buyers arrive at this decision with a budget, a use case and a vague sense that one of the three materials is the “responsible” choice. The honest answer is that none of them wins outright. Non-woven polypropylene, cotton canvas and paper each solve a different problem, and the right pick depends on how many times the bag will be used, what it has to carry, how it will be branded and what it costs you to ship it across an ocean.

At a glance

	Non-woven PP	Cotton canvas	Paper
Relative unit cost	Lowest	Highest	Low to mid
Typical load	5–15 kg by fabric weight	10–20 kg	3–8 kg
Reuse life	Months to years	Years	Single use to a few uses
Wet performance	Water-resistant; laminated is more so	Absorbs, then dries	Fails when wet
Best print	Screen; photographic via lamination	Screen, embroidery	Offset, foil, spot UV
Weight per bag	Light	Heavy	Light to mid
Folds flat for freight	Yes	Yes	Yes, but crush-sensitive
Kerbside recycling	Limited — PP #5, varies by area	Not kerbside; long life instead	Widely accepted

Non-woven polypropylene

Non-woven bags are made from polypropylene spunbond — fibres bonded by heat and pressure rather than woven on a loom. That production route is why they cost what they do: the fabric is made and finished in a continuous process, with no spinning or weaving stage.

Where it wins. Cost per bag at volume, by a clear margin. It is light, so it barely moves your freight bill. It is water-resistant out of the box and can be laminated for a glossy or matte finish with full-colour photographic print. It folds completely flat, survives repeated grocery loads at the right fabric weight, and takes a screen print cleanly.

Where it loses. It does not feel like a textile in the hand — buyers moving up-market usually notice. Kerbside recycling acceptance for PP #5 is inconsistent between municipalities, so it is not a material you can claim is universally recyclable in practice. And the cheapest grades feel exactly as cheap as they are, which is why fabric weight matters so much.

Specify carefully. Fabric weight is the single biggest lever: 60–70 gsm for a giveaway, 80–90 gsm for a supermarket carrier, 100–120 gsm for retail packaging. The GSM guide covers what each weight actually carries.

Cotton canvas

Canvas bags are woven cotton, specified in ounces per square yard — 8 oz for a light tote, 12 oz for everyday retail, 16 oz for a bag that will outlast the campaign that produced it.

Where it wins. Perceived value. A heavy canvas tote reads as a product rather than as packaging, which is why it survives as a merchandise item people actually buy. It carries the most weight, takes embroidery and screen print beautifully, and washes.

Where it loses. It is several times the unit cost of non-woven and it is heavy, which compounds: more expensive to make and more expensive to ship. Cotton cultivation is water and land intensive, so the environmental case only stands up if the bag is genuinely used hundreds of times — a canvas tote in a drawer is worse than a non-woven bag used weekly for two years.

Specify carefully. Weight in ounces, whether the handles are self-fabric or webbing, and the stitching at the handle join — that is where cheap canvas totes fail first.

Paper

Paper bags split into kraft, which is unbleached and structurally strong, and coated art paper, which is smooth and takes photographic print.

Where it wins. Print quality and finishing. Nothing else takes offset printing, foil stamping, spot UV and embossing the way coated paper does, which is why boutique and cosmetics packaging still lives here. Paper is also the most widely accepted material in kerbside recycling, and it carries an intuitive “not plastic” perception at the point of handover.

Where it loses. Water. A wet paper bag fails, and it fails suddenly. Load capacity is the lowest of the three, handles are the weak point, and the bags are crush-sensitive in transit so they cost more to pack and ship safely per unit of usable volume.

Specify carefully. Paper weight in gsm, handle type — twisted paper, flat paper, cotton rope or ribbon — and whether the base is reinforced. Ask about the handle attachment method; glued handles on a heavy bag are a predictable failure.

Think in cost per use, not cost per bag

The unit price comparison is misleading on its own. A paper bag that is carried home once and recycled has done its job. A non-woven bag used weekly for two years has done that job a hundred times. A canvas tote used for five years has done it several hundred times, at maybe eight times the unit cost.

Run the arithmetic against your actual scenario. For a conference giveaway where realistically most bags are discarded within a week, the cheapest material that survives the event is the rational choice, and paying for canvas is paying for a landfill item with better stitching. For a supermarket loyalty programme where the bag is meant to replace dozens of single-use carriers, durability is the whole point and under-specifying the fabric weight defeats the exercise.

What each material does to your freight bill

On a container of finished bags, material weight matters more than most buyers expect. Non-woven is the lightest for a given bag size, so you fit more billable units into the same cubic metres. Canvas is dense; the same carton count weighs substantially more and on sea freight you may hit a weight limit before you fill the space. Paper sits in between but needs more protective packing, so its usable density is lower than the raw weight suggests.

If you are importing regularly, ask for the carton dimensions, pieces per carton and gross weight at quotation stage rather than after the order is placed. It changes the landed cost comparison more often than people assume.

Branding: what each surface can actually do

Non-woven takes solid screen-printed colour well and photographic print only through lamination. Canvas takes screen print and embroidery, with a natural, slightly textured result that suits heritage and craft positioning. Paper takes everything — the full offset and finishing repertoire — which is why luxury retail has never left it.

If your artwork is a photographic image and your budget is non-woven, the route is a laminated bag rather than a direct print. The printing methods guide explains the trade-offs and where each method’s setup cost falls.

The environmental question, honestly

There is no version of this comparison where one material is simply better. What the published life-cycle work consistently shows is that the number of uses dominates every other variable. A material with a higher production footprint can come out ahead if it is genuinely reused enough times, and a low-footprint material used once does not.

What we can say factually about each: polypropylene is a recyclable polymer (resin code 5) but kerbside acceptance varies widely by municipality; conventional cotton is water and land intensive to grow, with organic and recycled-content options available at a cost premium; paper is the most widely accepted in kerbside collection and is commonly available with FSC-certified fibre. Recycled-content polyester (RPET) sits alongside these as a fourth option that uses post-consumer bottle feedstock.

What we will not do is put a claim on your bag that we cannot evidence. If your market requires a certified statement — FSC chain of custody, recycled content verification, compostability to a named standard — that has to be arranged with documentation for your specific order, and the cost and lead time are confirmed in writing before production. Unsupported wording on packaging is a live regulatory risk in the EU and UK, and increasingly in North America.

Regulatory context

Single-use plastic carrier bag restrictions now exist in many markets, but the definitions differ. Some jurisdictions classify bags by thickness, some by material, some by a reusability test with a specified number of uses. Non-woven PP is commonly treated as a reusable carrier rather than a single-use bag, but that is not universal and it is not something a supplier should promise on your behalf.

If you are importing into a market with carrier bag legislation, confirm the local definition with your own compliance adviser before finalising the specification. We can build to whatever thickness, fabric weight or marking requirement you give us; we cannot tell you what your regulator will accept.

Choosing by use case

Scenario	Usual choice	Why
Supermarket reusable carrier	Non-woven 80–90 gsm	Best cost per use at grocery loads
Trade show and conference giveaway	Non-woven 60–80 gsm	Lowest cost at high volume, light to ship
Retail packaging, fashion and cosmetics	Laminated non-woven or art paper	Photographic print and premium finish
Merchandise people keep	Cotton canvas 12–16 oz	Perceived value and long life
Bakery, takeaway and gift	Kraft paper	Recyclability and the right visual register
Wine and bottle presentation	Non-woven wine bag or rope-handle paper	Divided structure and load stability
Grocery checkout vest bag	Non-woven t-shirt bag	Fast handling, low cost, reusable

Frequently asked questions

Which material is cheapest per bag?

Non-woven polypropylene, at almost any volume. Paper is next, and cotton canvas is the most expensive by a wide margin because of both the raw material and the weight.

Are non-woven bags recyclable?

Polypropylene is a recyclable polymer with resin code 5, but whether your local kerbside collection accepts it varies by municipality. That is a meaningful distinction: recyclable as a material is not the same as recycled in practice, and we would not advise printing a blanket recycling claim on the bag without checking your target market.

How many times does a bag need to be reused to be worthwhile?

It depends on the material and the study you read, but the direction is consistent: heavier materials need more reuses to break even against a lightweight one. This is why the realistic reuse rate in your specific scenario matters more than the material choice itself.

Can I get an organic cotton or recycled-content version?

Yes. Organic cotton canvas, recycled-content RPET fabric and FSC-certified paper are all available. Each carries a cost premium and, where you need a certified claim, a chain-of-custody requirement that is arranged per order with documentation.

Which material handles wet weather?

Non-woven, and laminated non-woven in particular. Canvas absorbs water and dries, which is inconvenient but not a failure. Paper does not cope.

Can I mix materials in one order?

Yes. Buyers frequently run non-woven for volume handout and a smaller canvas or paper run for premium customers or VIP packaging. It is quoted as separate lines with separate specifications and tooling.

Next step

Tell us the use case, the quantity range and the market it ships to, and we will come back with a specification in each material worth comparing, so you can see the trade-off in real numbers rather than in principle. Request a quote.