The History of Dichroic Glass

Dichroic glass contains many micro-layers of metal oxides which give the glass color changing or dichroic optical properties. The invention of this glass is often erroneously credited to NASA, which developed it for use in filters. Dichroic glass dates back to early times and since then has been presented in different forms.

What Is?

"Dichroic" is derived from Greek roots, and means "two-colored." Dichroic glass is created by vaporizing metallic oxides and then allowing the molecules to be deposited on the surface of sheet glass. Time and temperature are of major importance and determine the thickness of the deposits on the glass. Anywhere from 15 to 50 different layers of deposited, alternating, metallic oxides may be required. The total thickness of the oxide layers are kept at, or under, 70 nanometers---1,000 times the thickness of a human hair. Dichroic glass' most distinctive feature is its ability to appear to have more than one color when viewed from different angles. Its colorful properties are the product of light manipulation, like a prism. "Thin film physics", or complex light interactions, result in the multiple color effect of not just dichroic glass but soapy bubbles, oil slicks and dragonfly wings.

Early Times

The first two forms of dichroic glass (fulgurite and obsidian) were naturally manufactured. Fulgurite; the byproduct of lightning striking sand, is commonly referred to as petrified lightning. Obsidian, which the byproduct of heat of a volcanic eruption fusing rock and sand, was fashioned into knives, arrowheads and jewelry during early times. The exact date of when, where or how humans first manufactured dichroic glass is extremely difficult to pinpoint. Around 3000 B.C. dichroic glass in the form of fused glaze was introduced. Next, glass vessels were produced in Egypt and Mesopotamia around 1500 B.C. Around 500 B.C. countries lining the eastern shore of the Mediterranean Sea formed a dichroic glass-making epicenter. Around 30 B.C., production became easier, faster, and cheaper resulting in dichroic glass availability to the common man and not just priests and the ruling classes. In the first four centuries of the Christian Era glass makers manufactured transparent dichroic glass, dichroic glass jewelry, paintings, and dichroic gilding.

Middle Ages

Following the time of the Crusades (A.D. 1096-1270), the 1290's developed an elaborate dichroic guild system of fused glassworkers in Venice. Here, Cristallo fused glass---a near colorless and transparent glass blown to extreme thinness in a myriad of shapes---was perfected. The offspring of Cristallo was intricate lacework patterns on goblets, jars, bowls, cups and jewelry. By the 1400's and 1500's, Germany and other European countries entered the industry. Also around this time many Venetians migrated to northern Europe. Here, they established glass factories that produced glass jewelry in the Venetian style. Bohemia in the 1600's perfected a new type of dichroic glass that was good for engraving. In 1674, George Ravenscroft an Englishman patented a type of dichroic glass with a different set of ingredients that included lead oxide.

20th Century

A vacuum deposition process emerged in the 20th century for creating dichroic glass. This process of adding layers of metallic oxides on top of glass goes back to the 1950's and 1960's. The National Aeronautics and Space Administration (NASA), defense contractors and the Department of Defense began developing optical filters, cosmic radiation shields and many other items using this process.

Myths

Dichroic glass does not use paints, dyes, gels or any coloring agents. NASA did not invent dichroic glass.

References

• Trezora Glass: Dichroic Glass :: Definition, History, Properties and Use in Fused Dichroic Jewelry & Art Glass
• Five Elements Gallery + Studio: Dichroic Glass History