Defects of Sulpher Dyeing | Bronziness of Shades | Sulpher Black Tendering

Defects of Sulpher Dyeing:
They are mainly two defects which are common in Sulpher dyed textile materials:-
  1. Bronziness or Dullness of shades
  2. Sulpher Black tendering
Now they are Described below:-

A. Bronziness of Shades:
This is a common defect found in Sulpher dyed textile materials.

The causes are as below:-
  1. Excessive delay between lifting of the material from the dye bath and washing off.
  2. Exposure of goods to air while dyeing.
  3. Too much use of common salts as exhausting agents.
  4. Insufficient Na2S (i.e. reducing agent) in dye bath. As a result of which dye is incompletely reduced.
  5. Strong dye liquor in the dye bath.
The remedies are as below:-
  1. Good washing and dilute solution of Na2S (0.1%) at 300C or,
  2. A treatment with boiling soap solution or a strong Na2S solution or,
  3. A treatment with a solution containing 10% salponified palm oil at 600C or,
  4. Ammonia : 125-200 gm/100 litre or, 1.25-2 gm/litre
          T.R Oil : 200-300gm/100litre or, 2-3 gm/litre.
          Time : 15 minutes
          Temperature : Water Bath

B. Sulpher Black Tendering:
If Sulpher dyed textile materials are stored (weakening) tentering effect is seen on the cellulose. Due to storage a part of the Sulpher colour converts in to H2SO4 by oxidizing which in turn causes degradation of cotton by hydrolysis. It is a serious problem of Sulpher dyed goods.

The causes are as below:-
  1. Gradual oxidation of Sulpher to H2SO4 on storage.
  2. After treatment with copper salts causes rapid tendering.
  3. Presence of iron as an impurity causes rapid tendering.
  4. The method of oxidation for the recon version to insoluble form influence tendering.
The remedies are as below:-
  1. Treatment of dyed material with 1-3% K2Cr2O7 and 1-3% CH3COOH at 600C temperature for 30 minutes followed by through rinsing.
  2. Treatment with a little CH3COOH so that H2SO4 may be converted in to harmless acetic acid.
  3. Using 5 gm/litre soda ash after dyeing followed by drying without rinsing. 


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