Coating Retention
Yarn reinforcement processes apply protective starch or synthetic coatings to warp yarns to prevent abrasion during the high-tension yarn processing cycle. The sizing pickup ratio represents the weight of the dry size chemicals remaining on the yarn after sizing, expressed as a percentage of the unsized dry yarn weight.
Application Control
Maintaining the correct pickup level requires close control of the squeeze roller pressure and the temperature of the size bath. Linen yarn is composed of highly crystalline cellulose fibres which absorb sizing liquids less readily than cotton does. If the pickup is too low, the linen yarn remains hairy and breaks frequently under the action of the rapier loom.
Excessive coating makes the yarn too stiff, which reduces the flexibility required to run smoothly.
Fabric Finish
Weft insertion efficiency and the subsequent desizing process are directly affected by the consistency of this chemical coating. When the warp yarn carries an even amount of sizing, it glides through the loom harness with minimal friction. This uniform coating prevents yarn shedding, which would otherwise build up on the loom parts and cause fabric defects.
After the linen fabric is manufactured, the sizing must be completely washed out in the finishing mill before dyeing can occur. Importers often test finished fabric for residual starch to confirm that the desizing stage was successful. Poorly controlled sizing pickup leads to uneven dye absorption and blotchy fabric colors.
