What’s Dichroic Glass?
Dichroic glass is glass containing multiple micro-layers of metal oxides which give the glass dichroic properties. The invention of dichroic glass is often erroneously attributed to NASA and its contractors, who developed it for use in dichroic filters. Dichroic glass dates back to at least the 4th century AD as seen in the Lycurgus cup. Multiple ultra-thin layers of different metals gold, silver, metal oxides, titanium, chromium, aluminium, zirconium, magnesium and silica are vaporised by an electron beam in a vacuum chamber. The vapour then condenses on the surface of the glass in the form of a crystal structure. This is sometimes followed by a protective layer of quartz crystal. The finished glass can have as many as 30 to 50 layers of these materials yet the thickness of the total coating is approximately 30 to 35 millionths of an inch (about 760 to 890 nm). The coating that is created is very similar to a gemstone and, by careful control of thickness, different colors are obtained. Dichroic glass is now available to artists through dichroic coating manufacturers. Glass artists often refer to dichroic glass as “dichro”. The main characteristic of dichroic glass is that it has a transmitted color and a completely different reflected color, as certain wavelengths of light either pass through or are reflected. This causes an array of color to be displayed. The colors shift depending on the angle of view. The total light that hits the dicro layer = wavelengths reflected + wavelengths passing through the dichro layer. A plate of dichroic glass can be fused with other glass in multiple firings. Due to variations in the firing process, individual results can never be exactly predicted, so each piece of fused dichroic glass is unique. Over 45 colors of dichroic coatings are available to be placed on any glass substrate. Images can be formed by removing the dichroic coating from parts of the glass, creating everything from abstract patterns to letters, animals, or faces. The standard method for precision removal of the coating involves a laser. Dichroic glass is specifically designed to be hotworked but can also be used in its raw form. Sculpted glass elements that have been shaped by extreme heat and then fused together may also be coated with dichroic afterwards to make them reflect an array of colors.