Degumming
Boiling silk in a soapy or mildly alkaline bath to remove its gum, which makes the thread soft and shiny.
Also: boiling off, souring silk
Raw silk thread is covered with sericin, a stiff gum. In degumming, the yarn or the cloth is boiled in a bath with soap or a mild alkali, which dissolves the gum. The silk loses a good share of its weight, and what remains is soft, smooth and glossy. Most silk is degummed before dyeing, so that the dye can enter the fibre evenly. Some silk is left partly or fully gummed until after weaving, to give the stiff, crisp hand that organza and some kora sarees have. Careful degumming matters, as harsh boiling can harm the fibre.