Stripping Process of Sulpher Dyes | Topping Process of Sulpher Dyes

Stripping of Sulpher Dyes:
Unevenly Dyed shades on cellulosic materials with Sulpher dyes may be corrected by a treatment with a worm solution of Na2S in the presence of Albigen A (polyvinyl pyrolodine)

If this method is found to be in effective then the uneven dyed material may be treated with a solution of a NaOCl or bleaching powder (2-3 gm/Litre of available chlorine).

In some cases bleaching with KMnO4 solution may be effectively carried out. In other cases the dyed material may be treated with worm NaOCl solution in the presence of NaOH.

The uneven dyeing of material causes due to the following reasons:-

1. The oxidation of dye during dyeing when the material comes in contact with air.
2. Presence of gummy material on the fabric.
3. Defective Dye.

Topping of Sulpher Dyes:
Sulpher dyes act as mordents for the basic dyes. The cotton textile materials dyed with Sulpher dyes can be topped with basic dyes for brightening the shades. So, topping of Sulpher dyes is one kind of re dyeing by which required brighter shades are obtained.

For topping of Sulpher dyes, at first dyed materials (dyed with Sulpher dyes) is washed thoroughly to remove the alkali from the fabric. Then the fabric is treated with basic dye in a second dye bath containing acetic acid of alum. In this bath temperature is raised about 600C to control the exhaustion of basic dye. 


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