Dyeing and Printing
What this domain tests
This domain tests how colour is applied to textile materials and how fastness and pattern methods differ. Expect questions on dye classes, stage of dyeing, print methods and colourfastness.
Core rules
- Dyeing can occur at fibre, yarn, piece or garment stage. Fibre dyeing gives deep penetration; garment dyeing is flexible but can give uneven shade.
- Dye choice follows fibre: reactive, direct and vat dyes for cotton; acid dyes for wool and silk; disperse dyes for polyester and other synthetics. A mordant helps some natural dyes fix.
- Printing places colour in a pattern on the surface: block, screen (flat or rotary), roller, transfer and digital. Resist printing (batik with wax, tie-dye with binding) prevents dye reaching selected areas.
- Colourfastness is tested against washing, light, rubbing and perspiration. A good dye–fibre bond and correct after-treatment improve fastness.
Worked example
A cotton T-shirt must be bright, wash-fast and suitable for school. Choose a dye class and explain. Reactive dye is suitable: it forms a chemical bond with cellulose in alkaline conditions, so it gives strong colour and good wash fastness. Direct dye is simpler but often less wash-fast; vat dye is fast but more complex. The reasoning must link fibre (cotton = cellulose), dye chemistry and end use (frequent washing).
Traps
Do not use disperse dye on cotton as a first choice; do not confuse printing with dyeing the whole fabric; batik is resist printing, not a dye class. “Colourfast” is not absolute-it is fastness to a specified test. Do not ignore after-treatment, which removes unfixed dye.