Saturday, 4 July 2009

Defects in Sulphur Dyeing

Defects in Sulphur Dyeing

1. Tendering

Tendering in the fabric takes place because sulphur is converted into sulphuric acid after oxidation which is harmful for the cellulosic fibers. This defect can occur on account of not proper washing of the fabric after dyeing which results in retaining of sulphuric acid on the cloth.

2. Uneven Dyeing and Oxidation Marks

This may occur due to:

a. Lower strength of sodium sulphide

b. Using improper amount of sodium sulphide.

c. Sodium sulphide does not wash off fully after washing.

d. Variation in temperature.

e. If colors are not dissolved properly, or colors are not of good quality

f. If the chemical used for oxidation is not of good quality

g. Fabrics are not worked upon properly at the time of dyeing.

3. Bronziness

This defect normally occurs in heavy shades. Given below are the reasons:

1. More time gap between dyeing and washing

2. Using more of less strength sodium sulphide

3. Using more salt.

4. Oxidiser doesn't get washed off properly during washing

5. Sodium sulphide doesn't get washed off properly during washing.

6. More presence of iron and copper ions in water.

4. Poor colorfastness to rubbing

It depends upon:

a. type of color
b. Lower strength of sodium sulphide
c. Poor absorbency of the fabric
d. Fabric is not washed properly
e. The quality of soap used for washing is not proper
f. Dyeing bath made of iron instead of steel
g. Frequent addition of colors and chemicals
h. Using Cationic finishing agent in finishing also lowers the colorfastness to rubbing
i. Improper color solution, Improper material to liquor ratio etc.

5. Roughness in Fabric

1. Using more amount of sodium sulphide that doesn't get washed off during washing.
2. Heavier shade
3. Improper washing
4. Not using anionic softening agent in finishing
5. Not using wetting agent.

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