During dyeing, common defects include shade difference, color streaks and patches, reproducibility of shade, selection of dyes and auxiliaries, white spots, rotten cotton spots in scouring and bleaching, creases, alkali spots, yellow spots, alkali residue, wax streaks, singeing creases and conveyor marks. How should these defects be handled at the technical level, prevented and solved in production, so as to improve product quality and the one-pass dyeing success rate and achieve energy saving and consumption reduction?

For frequently reordered colors: the pretreatment process must be stable and consistent to ensure the same absorbency, whiteness and pH value of the semi-finished goods in every production. Before each dyeing, the laboratory must confirm the sample; dyes from different batches must be compared with small samples. If all checks pass, the one-pass trial success rate will be high, and production can even run without trial dyeing (note: production process and machine must be consistent).

For new colors: the laboratory must make small samples for confirmation and compare samples before dyeing. It is best for two different samplers to confirm the sample separately; if the two prescriptions agree, the first prescription is close to the target.

Key control points: pretreatment consistency, accurate weighing and dosing of dyes and auxiliaries, strict control of the dyeing curve (temperature, time, liquor ratio, pH), and stable machine condition. Regular calibration of instruments and recording of every batch build a data basis for continuous improvement.