Dichroic Glass

Dichroic glass is glass containing multiple micro-layers of metals or oxides which give the glass dichroic optical properties. The main characteristic of dichroic glass is that it has a particular transmitted colour and a completely different reflected colour, as certain wavelengths of light either pass through or are reflected. This causes an array of colour to be displayed. The colours shift depending on the angle of view. Dichroic glass is an example of thin-film optics.

Manufacture

Multiple ultra-thin layers of different metals (such as gold or silver); oxides of such metals as titanium, chromium, aluminium, zirconium, or magnesium; or 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. A protective layer of quartz crystal is sometimes added. Other variants of such physical vapour deposition (PVD) coatings are also possible. 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 may be obtained.

The total light that hits the dichroic layer equals the wavelengths reflected plus the wavelengths passing through the dichroic 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 colours of dichroic coatings are available to be placed on any glass substrate.

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