Fabric pH not adjusted: with today's stricter requirements for energy saving and emission reduction and the rising cost of water, semi-finished cellulose fiber fabrics such as cotton more easily carry alkali before dyeing and before final finishing. Even finished dyed goods with a fabric pH above 8 occur from time to time, sometimes above 9; continuous pad-dyeing lines are more affected than batch dyeing.

Alkali carried by the semi-finished fabric after dyeing and before finishing has a strong adverse effect on many finishing auxiliaries, sometimes long-term (for example, finished goods dyed with reactive dyes sensitive to alkaline hydrolysis may develop chalking or shade change months later because of the alkaline fabric).

Because the defects usually appear only in finishing, finding the real cause is difficult, and attention can be misdirected to the finishing auxiliaries.

1. Effect on some finishing auxiliaries: alkaline residue consumes softener, changes the effect of resin finishing, and affects the shade and fastness of subsequent processing.

2. Effect on dyes: for reactive dyes that hydrolyze under alkaline conditions, residual alkali can cause fading and shade change after storage.

Prevention: check the pH value of the semi-finished fabric before dyeing and before finishing; neutralize with dilute acid or a pH regulator when necessary; keep the washing process complete and stable; control the pH of the final finished goods within the required range (usually 5.5-7.5 for most fabrics).