Copper oxide, glass colorant

The addition of oxides to ceramic bodies and to glasses to produce color has been known since antiquity (2). The use of iron and copper oxides predates recorded history. Cobalt was introduced into Chinese porcelain about 700 AD. Chromium compounds have been used since 1800 AD. 

Of the important properties of glass, color is one of the most interesting. Color is usually achieved by the addition of various metal oxides. The strongest of these are titanium, vanadium, chromium, manganese, selenium, iron, cobalt, nickel and copper. Silver and uranium will give weak colors. Some of the rare earths are also used as colorants with sharp absorption bands in contrast to the broad bands given by most colorants. (4)... 

The precise nature of the colorant materials is unknown. The idea that oxidized or corroded bronze was used as a means of introducing copper as a colorant to ancient glasses was initially proposed by Geilmann... 

Copper oxide is used to make copper ruby glass. The red color is produced by... 

It is difficult to make copper ruby glass which will be transparent in thicknesses as great as 1/8 in. It is therefore generally flashed as a thin layer on a much thicker layer of colorless or opaque glass. The color ordinarily develops more rapidly and is more intense in lead glasses, and increased sihca tends to reduce the rate of color development. Tin oxide and additional reducing agents such as cream of tartar are always necessary. 

Cobalt ores are often found in association with copper(II) sulfide. Cobalt is a silver-gray metal and is used mainly for alloying with iron. Alnico steel, an alloy of iron, nickel, cobalt, and aluminum, is used to make permanent magnets such as those in loudspeakers. Cobalt steels are hard enough to be used as surgical steels, drill bits, and lathe tools. The color of cobalt glass is due to a blue pigment that forms when cobalt(II) oxide is heated with silica and alumina. 

Colored glazes are made with the addition of nearly pure oxides of manganese, copper, iron, chromium, cobalt, et cetera ) opaque glasses, ot enamels, by the addition of oxide of tin, or phosphate of lime for which see Porcelain True and Earthenware, Some of the ordinary lead glazes for soft porcelain are given below —... 

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