Pretreatment of Dyeing and Finishing

Before a cloth can be dyed, printed, or conditioned with special finished, it must go through a series of preliminary treatments, the reason why such treatments are necessary is to ensure that the dyeing, printing and/or finishing are acceptable, predictable and reproducible. The impurities present, either natural or man-introduced, must be removed. And then the materials are rendered absorbent and receptive in a uniform way. The preparatory treatments needed depend on the type of fibers in the material and particular dyeing and finishing treatments that are to be done. Preparatory treatments can be done on materials from fibers to yarns, fabrics, or garments. Most often the preparatory treatments are done on the material in fabric form.  Fabrics which have been prepared for dyeing and finishing must have sufficient absorbency and whiteness.

Fabrics which will be dyed or finished using padding techniques must be very absorbent because they must be completely wetted and saturated with chemical formulations which they may be in contact with for only a few seconds or less.

Fabrics being dyed using batch processes will be in contact with the chemical formulations for a greater length of time, and absorbency may not be as critical as in continuous processes.

Fabrics which will go into white products require a very high degree of whiteness.

Fabrics which will be dyed pastel or very bright shades also require a good level of whiteness since the base colour of the fabric will contribute to the final shade after the fabric is dyed.

Fabrics which will be dyed dark or dull shades require less whiteness than fabrics for white products or pastel shades.

The different type of fibers in the material will influence the preparatory processing. For example, the preparation requirements for cotton-containing fabrics are different from those for wool. Polyester, nylon and other fabrics. preparation of woven fabrics must include treatments to remove size materials. This is not required for knitted fabrics and carpets since no size is present in these materials. Knitted fabrics may contain large amount of lubricants which were added to make the fabric manufacturing process run efficiently.