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.
Blackening Brass
Dissolve pure copper in a mixture of nitric acid and water in the proportion of one part acid to four of water. Heat the article to be blackened over a Bunsen burner, dip it into the solution and again heat it over the flame. Upon the first application of heat the article will turn green, but this gives place in a few minutes to a dead black. On account of the heating this method cannot be employed for articles which have been soldered, although it is the very best for fine work of every description. Should a polished surface be preferable to a dead black, a coat of lacquer may be applied. For rough work, mix lampblack with gold size and apply with a soft brush. This mixture may be thinned with turpentine. If a gloss is desired add gold size, if a dull black add more lamp-black.
BREGUET, ABRAHAM LOUIS. Born in Switzerland in 1747 and died in Paris in 1823. An eminent watchmaker of French parentage, and the inventor of the form of hairspring of that name. He was endowed with great ingenuity and a taste for complicated and remarkable mechanisms.