Silk Scouring

Silk is degummed (removal of sericin) and subsequently, the natural color is removed. A degumming treatment can be either partial or complete which gives a typical silk luster and soft hand. Degumming of silk can be carried out as follows.
Assessment of scouring:
  1. Determination of weight loss %.
  2. Absorbency test.
Determination of weight loss %: The weight of unscoured and scoured sample is taken at the same MR% and from these data total weight loss % can be calculated. The weight of the scoured sample is less than the unscoured sample.
Standard weight loss % is 4-8% (Acceptable).
If it is 8% than we may say that the sample is well scoured but if it is >8% than it is not acceptable as it indicates that the fiber damage ahs taken place. If it is <4% it indicates that the sample is not well scoured and there are impurities still present in the sample.
Absorbency test:
  1. Immersion test: A sample is more absorbent when it is scoured. 1cm×1cm sample is placed on the water surface and time taken by it to be immersed is noted. The standard time is 5sec. If it is up to 10sec, we say than the sample is well scoured. It is >10sec then the scouring has not taken place properly.
  2. Drop test/spot test: Colored solution of 0.1% direct dye (red) is used. The solution is dropped on the sample by pippet and its absorbency is examined visually. The drop may be the following shape when scoured. If the drop is circularly then we may say that the sample is well scoured. If the drop is circular but small area, then we say that the sample is uniformly scoured but not well scoured. If the drop is almost circular then the sample is uniformly scoured too. If it is not circular, we say that the sample is not uniformly scoured.
  1. Wicking test: A sample of 18cm×5cm is taken and a mark is made at 1cm from bottom. The 1cm portion is immersed into 1% direct dye solution for 5min and then the distance travelled by the colored solution above 1cm is noted. The acceptable range is 30-50mm.

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