Question

Colour bleeding can be treated by soaking the fabric in water mixed with

• A. Salt + vinegar
• B. Vinegar + lemon
• C. Salt + baking soda
• D. Baking soda + vinegar

Hint:

Always soak new, bright garments (such as deep red or indigo handloom cottons) in a cold bath of water mixed with salt and white vinegar before their first wash to lock in the dyes.

Answer 1

The Correct Option is A

Step 1: Chemical Mechanisms of Color Bleeding:
Color bleeding occurs when loose dye molecules wash out of the fabric due to incomplete dye fixation or poor chemical bonding between the dye and fiber.

Step 2: Action of Salt:
Sodium chloride (salt) acts as an ionic electrolyte. In a wash bath, the sodium and chloride ions reduce the solubility of direct and reactive dyes in water, preventing the dyes from dissolving out of the fiber matrix.

Step 3: Action of Vinegar:
Acetic acid (vinegar) creates an acidic environment (lowering the pH). This is highly effective for protein fibers (such as silk and wool) that are dyed using acid dyes. The acid protonates the fiber's amino groups, forming a strong chemical bond with the anionic dye molecules, which locks the dye in.

Step 4: Evaluating the Combinations:
Therefore, a mixture of Salt + Vinegar is the standard home and industrial method for setting fabric dyes and treating bleeding.