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.
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Deep Black
To obtain a very deep black, add 1 pound of bark to the logwood, and proceed as in last receipt. 293. Drabs on Cotton, Silk and Wool, by one Process. Work for half an hour in 8 ounces copperas and 4 ounces tartar; lift and drain; then work for half an hour in 4 ounces logwood and 1 ounce bichromate of potassa; wash out and dry. By varying the quantity of logwood, and by introducing a little fustic or peachwood in combination with the logwood, a great variety of drabs, slates or fawns can be produced.
These few receipts for mixed fabrics will show the care required in such operations, although, by practice, they become comparatively simple. 294. To Detect Animal or Vegetable Fibres. Treat the fabric with bichloride of tin heated to from 130° to 150° Fahr., when the cotton and linen become black, and the wool and silk remain unchanged. 295. To Detect Mixed Fabrics of Cotton and Wool. Dip a piece of the cloth in bleaching liquor; after a little while the woolen turns yellow, and the cotton white, and may easily be distinguished.