Colour

Where colour goes in

Dye classes and fibres

Each dye class bonds to particular fibres, so the fibre decides the dye, and the dye largely decides the fastness.

• Reactive (cotton, viscose, linen, lyocell): bonds chemically with the fibre; bright shades, good wash fastness; the standard for cotton knits.
• Vat (cellulose fibres): made soluble by reduction, then oxidised back inside the fibre; very high fastness to washing and light; workwear, uniforms. Indigo for denim is applied the same way but is meant to fade.
• Sulphur (cellulose fibres): low-cost deep blacks, navies and browns; moderate fastness, poor resistance to chlorine.
• Disperse (polyester, acetate): applied at about 130 °C under pressure; good fastness on polyester.
• Acid (wool, silk, nylon): applied from an acid bath, bonding to the fibre’s amino groups.
• Pigment (any fibre): insoluble colour fixed to the surface with a binder; simple and universal, but it stiffens the hand and dark shades can rub off.

A blend needs a dye for each fibre: cotton-polyester takes disperse dye for the polyester and reactive dye for the cotton, in one bath or two.

Printing

• Flat screen: paste is pushed through a mesh stencil, one screen per colour; garment panels and short fabric runs.
• Rotary screen: cylindrical screens print continuously; economical for long fabric runs.
• Digital inkjet: no screens, unlimited colours, photographic detail; low set-up cost suits short runs and sampling, though cost per metre is higher.
• By chemistry: pigment prints sit on the surface and suit any fibre; reactive prints on cotton or viscose are steamed and washed off for a soft hand; discharge prints remove the ground colour of dyed fabric, or replace it, for soft prints on dark grounds.

On garments, plastisol ink (PVC particles in a plasticiser, cured by heat) sits on top: opaque, bright on dark fabric and durable, but heavier to the touch; specify phthalate-free plastisol. Water-based ink soaks into the fibre: soft and breathable, best on light cotton; on dark garments it needs a discharge or high-opacity base.

Colour approval

1. StandardThe buyer sets the target: a physical swatch, a Pantone textile (TCX) reference or spectral data.
2. Lab dipThe dyer colours the actual fabric or yarn to the standard and submits two or three options; the buyer approves one or asks for a correction.
3. Strike-offFor prints, a sample printed on the production fabric is approved for colour, registration and hand.
4. BulkEvery dye lot is measured against the approved lab dip and released, corrected or rejected.

• D65Average daylight, 6,500 K; usually the primary source
• TL84Store fluorescent, 4,100 K
• AIncandescent, 2,856 K

Colour is judged by eye in a light booth and measured with a spectrophotometer. The difference is reported as ΔE, most often by the CMC (2:1) formula of ISO 105-J03; a tolerance of 1.0 is common, tighter for critical shades. Metamerism means a pair matches under one light but not under another, because different dye recipes were used; checking under two or more sources catches it.

Every dye lot differs slightly. Large orders are sorted into shade bands, groups of lots close enough to sit side by side; all panels of one garment must come from one band, or a sleeve can differ from the body.