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.
Electrotype
A cast of metal upon a mould by galvanic action. A wax impression of the type or engraving is coated with black lead, washed with solution of sulphate of copper, and dusted with iron-filings, which leaves a film of copper on the surface, after which it is suspended in a bath of: sulphate of copper 2, sulphuric acid 1, water to stand it at 140 deg. Beaume, and connected with the negative electrode of a battery. The sulphate of copper is decomposed when the circuit is closed, the metallic copper going to the negative plate, which is the plumbago-mould.
The deposit or shell is afterwards backed with molten type-metal. See STEREOTYPE; TYPE.