Good Pretreatment

A good pretreatment is a prerequisite for producing high class fabrics in subsequent process stages. Pretreatment has several objectives. It must remove size, greases and waxes, so that subsequent processes can be carried out without danger. There should be high absorbency and no fiber tendering. The degree of whiteness should be uniform. It should remove busks from the fabric and render a low ash content. The effect should be uniform over the length, width an cross-section of the fabric with on marks or creases and it should produce a soft handle.

In the pretreatment process the following factors need to be emphasized.

1) Desizing means that the size is to be removed to the extent that subsequent processes can be carried out in the best possible manner and without difficulty. Desizing removes sizes such as starch, PVA, CMC and also greases and waxes.

2) Impregnation is important to achieve optimum liquor application .That means chemicals in the correct place .i.e, evenly distributed over the length, width and cross-section, only that amount of chemicals is necessary.and the highest possible liquor pick up- as much liquor as the fabric can carry without loss.

3) In the steam process chemicals that have been applied to the fabric are caused to react. For a successful steaming process and adequate dwell time in saturated steam conditions and stabilizing of the bleaching liquor in accordance with steam conditions are decisive.

4) Washing means removal of the separated size and the accompanying substances made soluble in the steaming process.