The fibroin present in the silk fibre is covered by a thin layer of sericin. This sericin present in the silk fibres greatly affects the handle, sheen and texture of the finished goods,. It gets necessary to remove the sericin from the silk fibres. The silk gets more soft, lustrous after the removal of sericin. The improved texture also results after sericin removal. This serricin is also known as silk gum.
Thus, we can say that the main objective of the degumming process is to get improved lustre, softness, and texture. “The process of removing the sericin or silk gum from silk fibre is called degumming”.
As mentioned above, the silk gum( sericin) in the silk fibres acts as a protecting cover in it. This layer of sericin is kept unremoved till fabric manufacturing ( weaving) if the fabric is woven with undyed silk. This silk gum is removed during fabric dyeing. If we weave the fabric with yarn-dyed silk, it gets necessary to remove the gum in yarn form.
During the degumming process, the yarn or fabric is treated with an alkaline ( sodium carbonate) and surfacing agent( sodium lauryl sulphate) . The required chemicals are dissolved in normal water. Some amount of hot water is added to it for proper dissolution of chemicals. This solution is boiled initially, the temperature is reduced. It remains still hot. Now the yarn or fabric is treated with this solution for 30 minutes. The silk is washed with hot water. Then it is neutralized with citric acid or any other suitable neutralizing agent ( acid).
There almost 15℅ to 25 % weight loss occurs after complete removal of sericin during degumming of silk.
WEIGHTING OF SILK FIBRE:
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