Calculating Loom Reed Width and Warp End Density for Plain Weaves
Derive loom reed width by compounding greige take-up and wet finishing contraction percentages onto target cuttable width while balancing dent air space ratios.
Caustic Desizing
Preparation Stage
Chemical preparation steps involve the removal of starch-based sizing agents from woven fabrics using alkaline solutions. Caustic desizing utilizes sodium hydroxide to swell the starch granules and break the adhesive bonds between the size and the yarn. This method prepares the material for subsequent scouring and bleaching.
Size Removal
Removal of the size is more aggressive than enzymatic techniques. During caustic desizing, the fabric passes through a hot alkaline bath where the starch undergoes degradation and becomes soluble in water. This process is particularly effective for heavy fabrics or those sized with modified starches that resist enzymes.
Fabric Preparation
Preparation of the fabric requires thorough rinsing after the alkaline treatment. If the caustic desizing remains on the fibers, it interferes with the pH balance of the dyeing phase. Quality controllers verify the removal of starch using an iodine test to ensure no blue or purple reaction occurs on the cloth surface.
The presence of residual alkali can also cause yellowing during drying or subsequent heat setting.
Process Control
Control of the process focuses on temperature and concentration to avoid damaging the cellulose. High heat speeds the swelling of the starch. Correct dwell times in the saturator or steamer prevent the degradation of the underlying cotton fibers.