A Grayish-Black Coloring on Copper.

Manufacturer and builder 4, 1887

A grayish-black coloring on copper, according to the Illustrierte Zeitung für Blechindustrie, may be obtained by placing the object for treatment, after being well cleansed, in a weak solution of liver of sulphur. When a caustic effect has, after a short time, been produced, the object is rinsed, slightly heated, and brushed with a stiff brush. This coating is said to be very durable.

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