What is mercerization? Explain the process and its effects on cotton.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Open in two lines. Mercerization is a permanent chemical finish in which cotton is treated with cold, concentrated caustic soda under tension. It gives lustre, strength and better dyeing.
2 · History. John Mercer found the effect in 1844; Horace Lowe later showed that tension gives a silky lustre.
3 · Draw the fibre before and after. [Sketch: twisted ribbon with kidney-shaped cross-section → smooth round rod with round cross-section and almost no lumen]
4 · Process.
Scoured cotton held under tension.
Cold caustic soda (about 18-25%) for a short time.
Washed under tension, neutralised with dilute acid, rinsed, dried.
5 · Effects.
Lustre: round fibre reflects light evenly.
Strength up by about a fifth.
Absorbency and dye uptake rise.
Smoother hand; permanent.
6 · Uses. Sewing and embroidery thread, poplin and sateen shirting, premium knitwear, table linen.
7 · Daily-life link. Mercerized thread and table linen stay bright through hot washes in hotels, hospitals and canteens.
8 · Close in one line. Mercerization permanently upgrades ordinary cotton in look, strength and colour.
Scoring tip: The before-and-after fibre sketch explains every effect; draw it first and refer to it.
