Home › Field notes › Colour Fastness Requirements for Backpacks: Routes and Grade Reading

Modular Bag Pro · 2026-10-11 · 2,625 words · 12 min read

Colour fastness requirements for backpacks state how much shade change and how much colour transfer each dyed component may show when it is rubbed, washed, exposed to light or wetted with perspiration, and they have to be written per component rather than per bag. A workable clause names the route, names the adjacent cloth used for the staining read, and states the lowest grade that clears the lot. Our production team books those reads during prototype work at 6–10 working days, extending to 12–15 when a fresh laminate enters the build, and repeats them on bulk by attribute inspection planned to ISO 2859-1 at an acceptance quality limit of 2.5. Orders begin at 500 pieces and bulk occupies 35–50 days. Scope stays civilian: commuting, worksite tools, hiking and first-aid modules, never weapon carriage, ballistic protection or defence certification.

What Colour Fastness Requirements Cover on a Finished Pack

A colour fastness requirement is two measurements sharing one name. The first is the change in the specimen's own shade after it has been through a route, read against a grey scale that steps from 1 to 5 in half steps, where 5 stands for no perceptible difference. The second is how much dye left the specimen and settled on an adjacent undyed cloth, read on a separate scale built for staining rather than for change. A shell that keeps its own shade perfectly can still fail the programme by marking a pale shirt, and the two failures need two different clauses.

One pack rarely carries one dyed material. A 600 denier polyester shell may be piece-dyed, the lining a cheaper yarn-dyed taffeta, the binding tape a third source, the 25 mm webbing a fourth and the hook-and-loop tape a fifth, with a printed label and a zipper tape taking the count to seven. Each substrate holds a different dyestuff class fixed by a different process, so a single line reading "colour fastness 4" leaves six of the seven uncontrolled. Shade matching between those seven is a separate problem again, and it is judged under a controlled light booth rather than by eye on a bench.

The clause therefore belongs in a grid: one row per component, one column per route, one named adjacent cloth for every staining read. That grid is also the artefact a laboratory needs, because a report reading "shell, rubbing, 4" without saying whether the cloth was conditioned dry or damp cannot be compared with next season's result, and comparison across seasons is the whole point of keeping records.

Selection rule: Write colour fastness as a component-by-route grid with a named adjacent cloth for every staining read, and send back any report that offers one grade for the whole pack.

Dry and Wet Crocking: Why Coated Shells Read Lower Than the Base Cloth

Rubbing, usually called crocking, is the fastest read and the one that reaches a complaint desk first. The route published as AATCC 8 draws a white cloth across the surface under a stated load and stroke length, once with the cloth dry and once after it has been wetted to a defined pick-up percentage. The dry pass catches loose surface dye and powdery finishing residue left by a weak wash-off; the damp pass catches dye soluble enough to migrate when a pack rests against a humid shirt on a long walk.

Coated constructions behave differently from woven ones. In a piece-dyed woven fabric the dye sits inside the fibre, so a proper reduction clear after dyeing lifts most of the loose fraction and the read holds steady for years. In a coated or laminated build the pigment sits in a surface film only a few tens of microns thick, and anything that softens that film can move the read down a full step months after the laboratory passed it: plasticiser drifting to the surface, solvent from a cleaning wipe, or simply heat inside a container during a 25–35 day sea leg.

Three controls follow cheaply. Ask for the wet read and the dry read as separate lines rather than one averaged figure. Ask for the panel to be cut from the finished laminate, never from the base cloth before coating. And ask for the whole sequence to be repeated after a heat-ageing step of at least 7 days at a temperature agreed with the laboratory in advance, because that step is what separates a stable finish from a migrating one.

Verdict: Judge rubbing on the finished laminate with the wet and dry passes reported separately and re-read after 7 days of heat ageing, rather than accepting a single dry figure taken on the base cloth.

Light, Perspiration and the Combined Read That Most Specs Miss

Light and perspiration attack different chemistry and are usually bought as one line. Light fastness exposes a specimen to a filtered xenon source under controlled humidity until a stated end point is reached, with the well-known procedure AATCC 16 and the xenon-arc reference ISO 105-B02 both in wide use; the read is shade change against the grey scale, and it is the route that governs a pack left on a dashboard or hung on a worksite fence for a summer. Perspiration instead wets the specimen with an acidic and an alkaline solution, holds it at body temperature for several hours against an adjacent cloth, and reads both change and staining, with AATCC 15 the common reference.

The gap most specifications leave open is the combination. A shoulder strap in July is wet with sweat and in full sun at the same time, and the two acting together degrade some dyestuff classes faster than either alone. Laboratories publish combined routes inside the ISO 105 family for exactly this case, and a programme selling into hot climates should ask for it by name instead of assuming that passing light and perspiration separately covers the pair.

Back panels and hip-belt linings deserve their own rows in the grid, because they carry sweat, sunscreen and body oil for hours at a time and they sit against clothing the customer cares about. A dark lining that bleeds onto a pale shirt is the single most expensive colour complaint in the category, and it is caught by one extra row on a grid that costs almost nothing to add.

Bottom line: Request light, perspiration and the combined light-and-perspiration route as three separate rows for every panel that touches skin or sun, and never let one result stand in for the other two.

Laundering, Chlorinated Water and Field Cleaning

Machine washing is rare for a loaded pack, but the claim still matters because care labels, healthcare wipe-down routines and poolside use all introduce chemistry that plain water does not. The domestic procedure reference ISO 6330 sets out how a specimen is washed, rinsed and dried, and the accompanying read is normally taken against a multi-fibre adjacent strip carrying several fibre types so that staining can be reported per fibre rather than as one average. That per-fibre breakdown is what tells you whether the dye moved onto acetate, cotton or nylon, which in turn points at the dyestuff class.

Chlorinated water deserves a separate mention for resort, pool and municipal programmes. Chlorine attacks some dye classes directly and degrades elastane and certain coatings at the same time, so a pack that survives 5 domestic cycles can still chalk or shift shade after a season of poolside service. Seawater brings salt plus ultraviolet plus abrasion from sand, a combination no single laboratory route reproduces, which is why the specification should list the chemistry the programme expects rather than borrowing a generic apparel clause.

Where a bag will be wiped with disinfectant rather than washed, ask the laboratory to add a wipe solvent to the sequence. Alcohol-based wipes and quaternary disinfectants extract plasticiser and surface dye far faster than water does, and a healthcare or municipal buyer will reasonably expect the finish to survive a routine they perform several times a shift.

Takeaway: Name the actual chemistry the pack will meet — detergent, chlorine, seawater or disinfectant wipe — on the specification, and judge staining per fibre rather than against one averaged strip.

Reading Grades Without Over-Specifying a Backpack

The commonest error at specification stage is demanding the highest grade everywhere. Fastness routes trade against each other: a dyestuff selected for outstanding light performance on a polyamide shell can be mediocre at wet rubbing, and pushing every line to the top of the scale narrows the dyestuff field so far that shade matching across seven components becomes impossible and cost rises without any improvement the customer can see. The right grade is the one that matches the consequence of failure, and consequence differs by panel.

A lining against pale clothing carries a staining risk that a customer notices immediately, so that row justifies a demanding read. The underside of a top lid, seen by nobody, does not. Printed logos sit in a third category again: they are a film sitting on the fabric rather than a dye inside it, so they are judged by adhesion and by the read after rubbing, not by the same clause as the shell.

Judgement: Set each grade from the consequence of failure on that panel — demanding for a lining resting against pale clothing, moderate for a lid underside nobody sees — and never push every row to the top of the scale, since doing so shrinks the dyestuff field until matching seven components becomes unachievable.

Why Coated and Laminated Shells Fail Differently From Woven Cloth

A laminate puts pigment and polymer in a surface film, and every failure mode of that film becomes a colour failure. Plasticiser migration brings dye to the surface where a rubbing pass can pick it up. Hydrolysis, driven by humidity and time, breaks down ester-based polyurethane films so the surface goes tacky and then chalky, and the chalk reads as a shade change even though no dye has moved. Abrasion removes the film locally and exposes a paler base coat or a white scrim, which customers describe as fading when it is actually wear.

Thermoplastic polyurethane films resist hydrolysis better than ester-based polyurethane coatings and stay flexible at low temperature, which matters for programmes shipping into cold regions; plasticised polyvinyl chloride stays cheapest and softest but carries the plasticiser migration problem described above. Film thickness moves the result as well: a heavier film hides the weave and holds more pigment, and a thin film over a dark base cloth shows every scratch as a pale line.

Laser-cut attachment panels add one more mechanism, because the cut edge is bare polymer with no fibre to hold anything, and it is the first place a rubbed read drops. Any pack using a cut grid should have the edge condition photographed at inspection and the same edge re-read after conditioning.

Spec rule: For a coated or laminated shell, specify the film chemistry and thickness alongside the fastness grades, and re-read the cut edge and the folded edge separately from the flat panel.

Return Causes That Trace Back to a Colour Fastness Gap

Returns desks rarely report "poor colour fastness"; they report a shirt with a mark on it, a panel that no longer matches the one next to it, or a print that has gone. Each of those maps to a clause that was either missing or written too loosely to be tested, and the mapping is what turns a complaint into a specification change rather than a debate.

Notice how many of these share a root cause: the component was specified by colour name rather than by route and grade. A webbing tape ordered as "black" has no fastness obligation at all, and the cheapest tape that looks black will be supplied.

Writing the Requirement, Retaining Evidence and Programme Gates

Programme work is coordinated through our SGS-verified production base, where 137 people operate 7 production lines and 149 machines across a 4,950 m² floor, with nominal capacity of 200,000 units per month. The founder has worked in bag production since 2004 and the company was established in 2014. Each colour decision is evidenced in sequence: laboratory dips, a prototype build, a pre-production sample signed off against the grid, then bulk, where attribute sampling follows AQL 2.5 under ISO 2859-1 level II, with Critical defects tolerated at zero, Major at 2.5 and Minor at 4.0. Reports are retained against the dye lot number so a complaint two seasons later can be traced to a batch.

Commercial gates are predictable and should be written into the sourcing calendar. The order floor is 500 units per colour, prototyping occupies 6–10 working days for a conventional build and 12–15 where a new laminate or a new print is involved, and bulk takes 35–50 days after sample approval. Sampling carries a fee of USD 50–150 per style, refundable against the order, and new tooling or screens run USD 300–2,500. Budget figures come back in 24–48 hours and remain indicative only; terms are quoted FOB Xiamen with T/T 30/70.

Freight planning changes when colour is critical, because a long hot transit is itself a conditioning step. Sea freight runs 25–35 days, air 5–8 days and courier 3–5 days; a 20GP holds roughly 28 CBM and a 40HQ roughly 68 CBM. Where a programme ships a pale colourway into a hot market, air freight shortens the heat exposure even though it costs more per unit, and that trade belongs in the sourcing decision rather than in the complaint file.

Colour control sits alongside the rest of the build rather than apart from it. Attachment grid geometry is treated in the MOLLE system reference, panel layout for tool-heavy loads in the work pack section, and sun-exposed carry in the hiking pack section; bespoke colourways route through the custom modular programme. Test scope and quotation detail are listed under our services, and related reading sits in the blog index.