Notes on reactive dyeing operations. According to market surveys, reactive dyes are among the most widely used dyes today. This article summarizes 10 common operational mistakes and their solutions.

1. Why should the dye be pasted with a little cold water first, and why must the dissolving temperature not be too high?

(1) Pasting with a little cold water first wets the dye granules thoroughly. If the dye is poured directly into water, the outer layer forms a gel that wraps the granules, so the inside is hard to wet and dissolve. So paste with cold water first, then dissolve with hot water.

(2) If the dissolving temperature is too high, the dye hydrolyzes, lowering the fixation rate.

2. Why add dye slowly and evenly? To prevent the dye from exhausting too fast. If all the dye is added at once, the exhaustion rate is too high, making the outer layer of the fiber deeper and the inside lighter, causing color patches or streaks.

3. Why hold for a certain time (about 10 min) after adding the dye before adding salt? Salt is an exhausting agent. Giving the dye time to level on the fiber before exhaustion reduces uneven uptake.

4. Why control the temperature of the dye bath strictly? Reactive dye fixation is sensitive to temperature; too high a temperature accelerates hydrolysis, too low reduces fixation.

5. Why wash thoroughly after dyeing? To remove hydrolyzed dye and alkali, improving fastness and preventing chalking.

6-10. Other common mistakes: using hard water without softening; not controlling the liquor ratio; ignoring the pH value; treating samples and production differently; and not keeping machines clean between batches. The solutions are to control water quality, follow the process curve, and standardize operations.