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.
Brass Mirrors
These mirrors are of classical antiquity, and were made from an alloy known as speculum metal, which produces a very hard metal with great reflecting power; but it is now very seldom met with. A good speculum metal, very white and hard as steel, is composed of equal parts of copper and tin. Copper 7, tin 4, zinc 3, form an alloy of a light yellow color, possessing much lustre. This alloy is sometimes made from copper 2, tin 1, with the addition of 1/16 arsenic. Lord Rosse's composition was: copper 252.8, tin 117.8. See SPECULUM METALS; ROSSE'S TELESCOPE; BRASS.