Fabrics, Preparation, and Pre-treatment
What the exam tests
This domain covers fibre identification, fabric selection, and the wet preparation that makes cloth ready to print. Questions often ask what each stage removes and what happens if a stage is skipped.
Core rules
- Cotton is the commonest block-printing fabric; silk, rayon, wool, and blends are also used but need fibre-specific preparation.
- Desizing removes sizing (starch, PVA, or gum) applied during weaving; if left, paste sits on the size and crocks or washes out.
- Scouring removes waxes, pectins, oils, and dirt with alkali and detergent; it improves absorbency.
- Bleaching removes natural colour so dyes show cleanly; over-bleaching can damage cellulose.
- Mercerising cotton with caustic soda improves lustre, strength, and dye uptake; it is not a substitute for scouring.
- Silk degumming removes sericin; wool is scoured gently to avoid felting.
- Fabric should be neutral, dry, and flat before printing; residual alkali can shift reactive dye shades.
Worked example
A cotton sheeting prints pale and patchy. The printer used loom-state cloth without desizing. Reasoning: the starch size blocks dye penetration and the paste sits on the surface; the correct response is to desize, scour, rinse, and dry, then re-proof.
Traps
Do not assume ready-for-dyeing means fully prepared. Do not over-bleach to get whiteness. Do not print on damp cloth: it dilutes paste and causes bleeding.