Question

In the pad-steam process of vat dye, intermediate drying is carried out for \(\underline{\hspace{2cm}}\)

• A. Better fixation
• B. Prevention of pigment migration
• C. Increase in color depth
• D. Avoiding color change

Hint:

Whenever you see "intermediate drying" in a multi-stage padding process, the primary reason is almost always to prevent the migration of dyes or chemicals. Drying "locks" the substances in place before the next wet step.

Answer 1

The Correct Option is B

Step 1: Pad-Steam Process Overview: Fabric is padded with insoluble vat dye pigment, then undergoes chemical padding (reducing agent and alkali) and steaming for fixation.

Step 2: Intermediate Drying: A drying step can be added between dye pigment padding and chemical padding.

Step 3: Drying Step Purpose: Wet fabric with dye particles can experience uneven pigment distribution (migration) during the chemical padding. Intermediate drying fixes the pigment on fibers, preventing migration and ensuring even dyeing.

Step 4: Alternative Outcomes: While better fixation (A), increased color depth (C), and avoiding color change (D) are benefits of the complete process, intermediate drying specifically prevents pigment migration before fixation.