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Dichroic Glass

Posted by splashofice on September 9, 2010 at 4:51 PM

Dichroic glass

is glass containing multiple micro-layers of metal oxides which give the glass dichroic optical properties. The invention of dichroic glass is often erroneously attributed to NASA and its contractors, who developed it for use in dichroic filter. 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 colours are obtained.

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