Composition of Colored Glass

• Copper compunds in glass give it a light blue color. Kevin Jordan/Digital Vision/Getty Images

  The glass in the windows, containers and artwork of the modern world is primarily soda-lime glass--a compound formed using sodium carbonate, lime, silica, dolomite and aluminum oxide. Traditionally, much colored glass would be produced serendipitously, such as the black bottle glass made in 17th century England using sand with iron impurities. Nowadays, people specifically color glass using a variety of minerals or metal salts.

Green

• Ferrous and ferric iron oxides combined with chromium produce the green glass common in wine bottles. Chromium is a powerful colorant; excessive use results in black-colored glass. A yellowy green glass results from using uranium oxide. Uranium glass was invented in the 1830s and has the added attraction of glowing in the dark.

Blue

• The addition of cobalt oxide produces glass that is deep blue. There is evidence of cobalt being used in stained glass windows dated from the 12th century. Light blue results from using copper compounds. An example is the Egyptian blue glass that was popular during the Roman Empire.

Red

• The addition of gold chloride produces glass with a distinctive ruby red color. In English glasshouses this is referred to as Ruby Gold. Andreas Cassius first described the process in 1685 and the technique still remains in use. A cheaper alternative to the addition of gold is compounds made from copper or selenium.

Amber

• Glass makers can achieve amber color by combining iron sulfides with iron in the presence of a reducing agent such as carbon. The exact shade of amber depends on the amount of carbon added to the glass batch in the form of charcoal, coal or wood chips. Cadmium sulfides can produce a deep yellow color. Many countries now prohibit the use of cadmium due to its high toxicity.