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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To make Blue Stone
Sulphate of copper is known in commerce as Blue stone, Roman vitriol, and Blue vitriol, and may be prepared by exposing pure copper in thin sheets to the joint action of dilute sulphuric acid and air; or by treating freshly precipitated oxide of copper with diluted pure oil of vitriol; or by boiling the metal with oil of vitriol, either in the concentrated state or diluted with an equal bulk of water. These and removes the oil, grease and dressing which it has obtained in weaving; it is then thoroughly rinsed in clean water. Where there is a dash-wheel, it should be used for this washing. In consequence of the liquor often fermenting with the paste in the cloth, this process has been technically termed the rot steep.
If the cloth is to be dyed a dark color, no further preparation is needed; but if light, the cloth has to be bleached as follows: