Light color: insurance powder extraction under alkaline conditions, such as: caustic soda 2g/L+ insurance powder 4g/L 95℃ 30min→ hot washing → water washing
Dark color: reduction extraction + oxygen bleaching, such as: caustic soda 4g/L+ insurance powder 8g/L 95℃ 40min→ heat washing → oxygen bleaching → heat washing → water washing
Modification of dyed fabrics with vulcanized dyes is usually done by placing them in a reductant blank solution (6g/L full strength sodium sulfide) at the highest possible temperature so that the dyed fabrics are partially discolored and then redyed. In severe cases, sodium hypochlorite or insurance powder should be used.
Color drawing process for light fabric:
Color stain cloth → dip and roll more (sodium hypochlorite 5 ~ 6g/L,50℃) →703 steam box (2min) → wash fully → dry
Dark fabric color drawing process:
Color defect cloth → rolled oxalic acid (15g/L, 40℃) → drying → rolled sodium hypochlorite (6g/L,30℃×15s) → fully washed → drying
Intermittent color extraction process:
55% sodium sulfide crystal 5 ~ 10g/L; Soda ash 2 ~ 5g/L (or 36°Be NaOH 2 ~ 5ml/L); Temperature 80 ~ 100℃; Time: 15 ~ 30min; Bath ratio 1:30 ~ 40.