A buyer’s real question about colour is short. When the customer washes this, will it run onto her white towel? Will it fade? And what do I write into the specification so it does not happen?
The answer is set long before the garment is sewn. It is set by the fibre, by the dye class chosen for that fibre, and by how thoroughly the surplus dye was washed out afterwards. Everything else is detail.
Fibre decides which dye can be used
A dye has to have something to hold on to. Different fibres offer completely different chemistry, which is why one dye cannot serve them all.
- Cellulosic fibres — paxta, zig'ir, viskoza. The fibre carries hydroxyl groups. These can be made to react chemically with a dye, which is the basis of the best wash fastness available on cotton.
- Protein fibres — silk and wool. These carry amino and carboxyl groups, so they behave like a mild acid-base system. They take acid dyes, which are held mainly by ionic attraction.
- Polyester — has almost no dye sites at all and repels water. It is coloured with disperse dyes, which are pushed into the polymer at high temperature and then physically trapped there as it cools.
This is why a cotton dye will not colour polyester, and a silk dye will not colour cotton properly. It is also the root of most blend problems, further down.
Dye class decides how well the colour holds
Within a fibre, the choice of dye class is the single biggest lever on fastness.
On cotton, linen and viscose
Reactive dyes form a covalent bond with the fibre. The dye becomes part of the fibre, not a passenger on it. Properly applied and properly washed off, this gives very good wash fastness, and it is the normal choice for a garment expected to survive repeated home laundering.
Direct dyes are simpler and cheaper to apply, but they are only held by weak physical forces. Water-soluble dye sitting on the fibre surface is removed by repeated washing, so colour loss is expected rather than accidental. Direct dyeing is not the right choice for a shade you need to hold.
Vat dyes are insoluble. They are chemically reduced into a soluble form, absorbed, then oxidised back to the insoluble form inside the fibre, where they are effectively stuck. Wash and light fastness are generally strong.
Indigo is the well-known exception in that family. The molecule is large and stays near the yarn surface — the core of the yarn is left white. That surface layer is why indigo rubs off, and it is a property of the colouring method, not a fault in a particular batch.
On silk and wool
Acid dyes cover an enormous range. Some are excellent, some are poor, and solubility is a fair rough guide: a very water-soluble acid dye tends to keep leaving with the water. Silk in particular can look superb on the hanger and disappoint after washing, because the bond is an attraction rather than a chemical reaction. Wet fastness on silk deserves specific attention, taxmin emas.
Pigments, which are not dyes
A pigment has no affinity for any fibre. It is glued to the surface by a binder film. That is a real and useful technique, but it has one predictable consequence: what sits on the surface can be rubbed off the surface. Pigment colour crocks more than dyed colour, and the deeper the shade the thicker the pigment layer.
Unfixed dye is why the first wash bleeds
No dyeing fixes completely. In reactive dyeing, some of the dye reacts with water instead of with the cotton. That hydrolysed dye is coloured, it is stuck in the fabric, and it is not bonded to anything. It will come out — the only question is whether it comes out at the dyehouse or in the customer’s machine.
Removing it is the job of the rinsing and soaping steps after dyeing. It takes several rinses, some of them hot, because the rate of removal rises with temperature. Cutting that stage short is invisible on the shade card and obvious on the first wash.
So when a garment bleeds heavily once and then behaves, that is almost always surplus unfixed dye, not a wrong dye class. When it keeps bleeding wash after wash, the dye class or the fibre match is wrong.
Where blends and multi-colour pieces go wrong
A cotton and silk blend needs two dye chemistries in one fabric — one for the cellulose, one for the protein. Each is applied under conditions the other does not like. The usual approach is sequential: dye one component, then the other.
The risk is cross-staining. The cotton dye deposits on the silk, or the silk dye on the cotton, where it has no proper bond. It looks like colour. It behaves like surplus dye. Union shades on blends should be judged on wet fastness, not only on whether the two fibres match in tone.
The same logic applies inside a single piece. A print with a white ground beside a deep navy, a hazil with a white body and a dark contrast band, a scarf with a pale border — every one of these puts loose dye next to a surface that shows it. The failure is not that the navy fades. It is that the white goes grey-blue.
Anything sewn from more than one colour deserves the same question: what happens when these two are wet together?
Rubbing is the failure your customer will actually complain about
Colour transferring by rubbing is called crocking. It is tested dry and wet, and wet is always the harder result.
This is the complaint that reaches a brand’s customer service desk. Dark trousers on a light sofa. A deep-dyed bag against a white shirt. A kaftan marking the wearer’s skin at the neckline in hot weather. None of these involves a washing machine at all.
Two things make crocking worse, both predictable:
- Depth of shade. A deep colour needs more colourant, and more of it ends up near the surface. Black, navy and deep maroon are the usual offenders.
- Colour that sits on the surface by design. Pigment prints and indigo both do this.
A deep pigment print is therefore the hardest case in the range, and it is worth agreeing a realistic wet rub expectation for it in advance rather than discovering the number after production.
The shades that are hardest to hold
Shade matters as much as fibre. Deep navy, black and deep red need heavy dye loading, so surplus dye and surface dye are both higher, and both wash and rub results tend to fall. Indigo rubs by nature. Turmeric is worth naming because it looks so convincing and lasts so poorly — curcumin sits on the fibre rather than bonding into it, and it is very sensitive to light. A turmeric yellow can visibly dull after a short period outdoors.
Pale and mid shades are easier on every count.
Mercerisation, and why it helps the colour
Mercerisation treats cotton with caustic soda. The fibre swells permanently, and its cross-section changes from a flat, twisted ribbon to something rounder and smoother. Two things follow.
More of the fibre becomes accessible to dye, so uptake improves markedly. A given depth of shade can then be reached with less dye — which is helpful for fastness, because less dye means less surplus to wash out. Deep shades also become easier to reach at all.
Second, if the fabric is held under tension during the treatment, the smoother surface reflects light more evenly and the fabric gains lustre. Mercerised cotton simply looks richer in a deep shade.
How colour is tested, and how results are graded
The main international methods sit in the ISO 105 seriya. Name the part, not just “colour fastness”.
Yuvish
ISO 105-C06 covers colour fastness to domestic and commercial laundering, using a reference detergent. The specimen is laundered with specified adjacent fabrics under set conditions of temperature, alkalinity and abrasive action. It offers single and multiple test variants, so the conditions must be named — a result is meaningless without them. ISO 105-C10 is the older washing method using soap, or soap and soda. In the American system, AATCC TM61 is the accelerated laundering method.
Rubbing
ISO 105-X12 is colour fastness to rubbing. A standard white cotton cloth is rubbed against the specimen on a crockmeter, dry in one test and wet in another, and the staining on the white cloth is graded. AATCC TM8 is the equivalent crocking method; AATCC TM116 uses a rotary vertical crockmeter, which is designed for testing areas too small for the standard instrument — useful on a small print motif.
Light and perspiration
ISO 105-B02 assesses fastness to artificial light using a xenon arc lamp. ISO 105-E04 covers perspiration, in both acid and alkaline form, which matters for anything worn against the skin in heat.
Reading the grades
Results are read against grey scales, and this is the part worth understanding properly, chunki two different things are graded separately.
- Change in colour — has the specimen itself shifted? Graded on the grey scale of ISO 105-A02, dan 5 for no change down to 1 for severe change, with half steps between.
- Staining — has colour transferred onto the white fabric beside it? Graded on the grey scale of ISO 105-A03, again from 5 for no staining down to 1, with half steps.
A single number on a report is therefore incomplete. Ask which one it is.
Staining is usually reported against a multifibre adjacent fabric, specified in ISO 105-F10. This is a woven strip containing several different fibres in bands — paxta, poliester, polyamide, akril, wool or viscose, and an acetate — so one test shows which fibres the dye stains. That detail is directly useful: a dye that stains the polyamide band tells you what will happen to a nylon lining or a swim garment packed next to it.
Light fastness is graded on a different scale entirely. It uses blue wool references numbered one to eight, where each step is roughly a doubling of resistance. Do not compare a light fastness number with a wash fastness grade; they are not the same scale.
What the end consumer does to the garment
Laboratory conditions are controlled. Households are not, and the difference explains a share of complaints.
- Wash temperature. Hotter water removes more colour and moves it around more freely. The same garment that is stable in cool water can release dye in a hot wash.
- Hard water. Calcium and magnesium interfere with detergents and with the agents meant to protect colour, and can leave deposits that dull a shade. Buyers selling into hard-water regions see more colour complaints for the same goods.
- Detergent choice. Detergents formulated for whites commonly contain optical brighteners. They are intended to make white look whiter and are not made for coloured garments; over many washes they work against the appearance of a deep shade.
- Drying in sunlight. Direct sun is a fading exposure. A light-sensitive dye can lose noticeable brightness quickly this way, and consumers in hot countries dry outdoors as a matter of course.
None of this changes the chemistry of the dye. It changes how much of that chemistry the customer gets to see.
What to write into your specification
Vague requirements produce vague results. These are the points buyers commonly agree with a supplier before bulk, and each one closes a specific gap.
- Name the test method and its part. “Good colour fastness” spetsifikatsiya emas. “ISO 105-C06” hisoblanadi, and so is naming the conditions — temperature, and single or multiple test.
- Ask for shade change and staining as separate grades. A report giving only one figure is telling you half the story.
- Ask for the staining result across the multifibre bands, not as a single averaged number.
- Ask for dry and wet rubbing separately. The wet result is the one that predicts a complaint.
- Set expectations shade by shade, not one figure for the whole range. A pale print and a deep navy will not deliver the same grade, and a blanket requirement written for the pale shade will be missed by the navy. What is realistic depends on the shade, the dye class and how the garment is used — a scarf worn against a coat is a different case from a lined jacket.
- Specify the tested shade explicitly. A result on a standard shade is not a result on your colour. Deep shades in particular need testing on the actual production shade.
- For any piece with a white or pale ground next to a deep colour, call it out. Ask specifically for staining onto the light ground.
- For blends, ask how the two fibres were dyed, and treat wet fastness as the acceptance point rather than shade matching alone.
- For skin-contact garments and anything for warm markets, add perspiration to the list.
- For prints and deep bag or trim colours, treat rub fastness as the primary criterion, not a secondary check.
The useful habit is to think about the failure before the fabric exists. Ask what the customer will put this garment next to, wet, and specify the test that answers that question.
