Colour, dyeing, printing and finishing

Colour

Colour theory (hue, value, saturation), colour harmonies and psychology; colour fastness to washing, light and rubbing.

Dyes

• Direct and reactive dyes for cellulose (reactive dyes form covalent bonds – excellent wash fastness).
• Acid dyes for wool, silk and nylon.
• Disperse dyes for polyester (applied at high temperature).
• Vat dyes (e.g. indigo for denim).
• Natural dyes (plant and mineral sources) with mordants.

Dyeing stages

Fibre, yarn, piece or garment dyeing.

Printing

Block, screen (flat and rotary), digital and transfer printing; resist methods (batik, tie-dye).

Finishing

• Mechanical: calendering, raising (brushing), sanforising (compressive shrinkage).
• Chemical: mercerisation (cotton treated with sodium hydroxide for lustre and dye uptake), crease resistance, water repellency, flame retardancy, antimicrobial and stain-resistant finishes.

Environmental impact

Water use and pollution from dyeing; effluent treatment; eco-friendly dyes and processes.

Check yourself

1. Which dye class is used for polyester?
2. What does mercerisation do to cotton?
3. Name two resist dyeing methods.