12 September 2012

Weighting of Silk

Weighting of Silk:
The process of increasing the weight of the silk material is known as weighting of silk.

Object of Silk Weighting:
  1. After the processing of silk material, it loses about 25% of its weight particularly after degumming.
  2. This loss in weight leads to a great loss of money since they are very expensive.
  3. To compensate the loss, some weight is artificially added to the material by chemical means.
  4. During degumming of silk, a weight loss of 25% is normally observed in case of silk fabrics.
  5. Owing to the expensive nature of silk, it is necessary to compensate the weight loss. 
Silk Weighting
Other Objects:
  1. Weighting is also done to reduce limpness.
  2. To impart a bulky effect.
  3. To control the scroopy effect.
  4. To give body to the fabric.
  5. To give a greater filling capacity.
Silk Weighting Process:
Tin salts are widely used for silk weighting.

There are three methods which are followed:

1st method:
The silk is soaked with stannic chloride solution followed by fixation with sodium carbonate followed by soaping.

Marginal weight increase is observed but the strength is also adversely affected in this method.

2nd method:
  • The silk is soaked in stannic chloride and the fixed with sodium phosphate.
  • It is then washed and treated with little amount of sulphuric acid.
  • It is then soured, washed and taken out.
Even though increase in weight is considerable, the strength loss is still high in this method.

3rd method:
  • In this method the fixation is done with sodium silicate.
  • This brings out the required increase in weight without affecting the strength much.
Normal Method:
  • In the normal practice silk is soaked in stannic chloride solution called Picking.
  • Later it is treated with sodium phosphate called Phosphating.
  • The picking and Phosphating is carried out alternatively till the sufficient weight is achieved and the sequence is:
  • Picking washing - Phosphating - acidifying
  • Finally after sufficient loading it is treated with Sodium Silicate.
Chemistry:
Stannic chloride + sodium phosphate Tin phosphate

Tin phosphate + sodium silicate Tri silicate of tin 

http://textilelearner.blogspot.com/2013/01/weighting-of-silk-object-of-silk.html 

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