Chemical Treatment
Chemical immersion involves saturating cotton yarns or fabrics in a concentrated solution of sodium hydroxide to change the crystalline structure of the cellulose. During mercerization steeping, the flat, twisted cotton fibres swell into a cylindrical shape and lose their natural convolutions. This structural shift increases the surface area of the fibre, which leads to a higher affinity for dyes and a more lustrous appearance.
Solution Concentration
Caustic baths are typically maintained at a strength between twenty percent and thirty percent to ensure full penetration of the textile. Successful mercerization steeping requires precise temperature control because the exothermic reaction can damage the fabric if the heat is not dissipated. The duration of the soak determines the depth of the lustre and the eventual strength of the finished product.
Dimensional Stability
Tenter frames or rollers hold the fabric under high tension while the chemical reaction takes place. Without this mechanical restraint, the swelling caused by mercerization steeping would lead to significant shrinkage and a loss of fabric width. Rinsing the caustic solution away while the material is still under tension sets the new, smoother surface of the yarns.
Chemical Recovery
Modern mills use evaporation plants to reclaim the sodium hydroxide for reuse in subsequent batches.
