Short answer
Cotton and linen are cellulose fibres, dyed mainly with reactive dyes that bond chemically to the fibre, direct dyes that cling to it, and vat dyes — indigo is the best known — that are made soluble, absorbed and then locked in by oxidation. How a cotton or linen colour ages depends on which class was used: reactive and vat colours resist washing, while indigo is designed to rub off and fade. Light fades most dyes over time, and linen's own natural colour, from ivory to grey-tan, shows through pale shades unless it is bleached first.
Relative to other materials in this section, not a measurement of a particular product.
| Process | What you see | Driven by | Slowing it |
|---|---|---|---|
| Light fading | Paler, duller colour on exposed areas | Light (visible as well as UV) breaking down dye molecules | Lightfast dye classes; curtains lined; UV-filtering glass |
| Wash-down and abrasion | Fading at seams and edges; indigo wearing to pale blue | Removal of surface dye and fibre | Reactive or vat dyes; wash inside out |
Colours that work with cotton and linen (cellulose fibres) in a room
Cellulose has no electrically charged sites for dyes to cling to in the way protein fibres do, so cotton and linen use their own dye families. Direct dyes are water-soluble and are held by weaker attractions; they are easy to apply but bleed in washing unless after-treated. Reactive dyes, introduced in the 1950s, form covalent bonds with the cellulose and give bright colours with good wash fastness, and are now the workhorse for cotton. Vat dyes, including indigo, are insoluble pigments that are chemically reduced to a soluble form, absorbed, then oxidised back inside the fibre; they are very fast to washing and light. Sulphur dyes give economical blacks, navies and browns. Pigment printing sits on the surface in a binder rather than in the fibre.
Denim is the exception that proves the rule. Indigo is applied to the warp yarns in repeated dips, oxidising to blue each time, so the colour builds up on the outside of the yarn while the core stays pale — ring dyeing. Rubbing and washing strip the outer layers and expose white core, which is why denim fades to paler blue at seams, knees and pockets, and why stone-washing, enzyme washing and abrasion are used to age it deliberately. Indigo's wash and rub fastness on cotton is therefore poor by design, while its lightfastness is fairly good. Garment-dyed and pigment-dyed casual cottons are also made to fade quickly for a worn-in look.
Flax fibre is not white. Depending on the plant, retting (the controlled rotting that frees the fibres from the stem) and processing, undyed linen ranges from ivory and ecru to oatmeal, tan and silvery grey. Bleaching whitens it but takes several stages and weakens the fibre somewhat, so 'natural' linen is sold in its own colour and pale dyed linens often carry a warm undertone from the flax. Linen's smooth, long fibres give a slightly higher lustre than cotton and a crisp handle; it takes dye less evenly than cotton, which gives some linens a characteristic slightly irregular, heathered depth. Mercerisation of cotton — treatment with caustic soda under tension — swells and rounds the fibres, raising lustre and increasing dye uptake.
In light, both the dye and the fibre change. Conservation guidance puts many dyes in textiles among the most light-sensitive colourants, and notes that visible light, not only ultraviolet, does much of the fading — UV often contributes less than half. Cotton and linen fibres themselves weaken with long exposure. Curtains fade on the window side and along folds; sofa arms fade where the sun falls. Washing removes unfixed dye (poorly fixed reds and navies are the usual culprits for colour run), detergents with optical brighteners add a bluish fluorescence to pale cottons, and abrasion lightens colour by raising fibre ends that scatter white light. Chlorine bleach attacks many reactive dyes, and hard water and residues can dull colours over repeated washes.
| Class | How it is held | Typical use | Wash fastness |
|---|---|---|---|
| Reactive | Covalent bond to cellulose | Most bright and pale cotton colours | Good to excellent |
| Direct | Adsorbed; weaker attraction | Economical shades, linings | Moderate unless after-treated |
| Vat (incl. indigo) | Insoluble pigment regenerated in the fibre | Workwear, denim, high-fastness colours | Excellent (indigo rubs off by design) |
| Sulphur | Insoluble dye oxidised in the fibre | Blacks, navies, browns | Good; may fade in light and bleach |
| Pigment print or dye | Surface binder | Prints, garment 'washed' colours | Varies; rubs and fades readily |
Why: Unfixed or direct dye bleeding in warm water.
Fix: Wash deep colours separately and cool for the first washes; use a colour-catcher sheet.
Why: Folds received different light doses; visible light fades dyes, not only UV.
Fix: Line curtains; rotate or draw them evenly; UV-filtering glass reduces but does not stop fading.
Why: Undyed flax varies by harvest and retting.
Fix: Approve a length from the actual bolt; order everything from one dye lot.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactModerate evidence
Cellulose fibres such as cotton are dyed with a range of dye types including vat dyes and synthetic reactive and direct dyes; vat and reactive dyes on cotton give excellent wash fastness, while indigo has poor wash and rub fastness on denim.
Source: Dyeing
FactModerate evidence
Textile dyes are classed by application as acid, basic, reactive, vat, disperse and direct, chosen for their affinity and bond stability with the fibre; roughly a fifth of dye used in textile dyeing is not fixed and leaves in wastewater.
Caveat: The unfixed share varies widely by dye class and process; it is an overall estimate.
FactStrong evidence
For light-sensitive colourants, ultraviolet usually contributes less than half of the fading and often only about a tenth; visible light causes much of the damage, and long exposure also weakens cotton, wool, silk and paper fibres.
Source: Agent of deterioration: light, ultraviolet and infrared
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.