Dichroic Glass

Dichroic glass is glass which displays two different colours by undergoing a colour change in certain lighting conditions.

One dichroic material is a modern composite non-translucent glass that is produced by stacking layers of glass and micro-layers of metals or oxides which give the glass shifting colours depending on the angle of view, causing an array of colours to be displayed as an example of thin-film optics. The resulting glass is used for decorative purposes such as stained glass, jewellery and other forms of glass art. The commercial title of "dichroic" can also display three or more colours (trichroic or pleochroic) and even iridescence in some cases.

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 - 50 layers of these materials, yet the thickness of the total coating is approximately 30 - 35 millionths of an inch (about 760 - 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.

Dichroic glass is now available to artists through dichroic coating manufacturers. Glass artists often refer to dichroic glass as "dichro".

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 hot-worked 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 colours.

Information courtesy of https://en.wikipedia.org/wiki/Dichroic_glass