Important: Safety Warning
This page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes.
This information has been left in for historical purposes but should not be acted upon.
Home › Recipes › To bleach silk
To bleach silk
Take a solution of caustic soda, so weak as to make only a fourth of a degree, at most, of the areometer for salts, and fill with it the boiler of the apparatus for bleaching with steam. Charge the frames with skeins of raw silk, and place them in the apparatus until it is full; then close the door and make the solution boil. Having continued the ebulution for twelve hours, slacken the fire, and open the door of the apparatus. The heat of the steam, which is always above 250 degrees, will have been sufficient to free the silk from the gum, and to scour it. Wash the skeins in warm water; and having wrong them, place them again on the frames in the apparatus to undergo a second boiling. Then wash them several times in water, and immerse them in water somewhat soapy, to give them a little softness. Notwithstanding the whiteness which silk acquires by these different alterations, it must be carried to a higher degree of splendour by exposing it to the action of sulpheric acid gas, in a close chamber, or by immersing it in sulphurous acid, as before recommended for wool.