Today's Jewelry Boutique

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 attributed to NASA and its contractors, who developed it for use in dichroic fibers, however, dichroic glass dates back to at least the 4th century AD as seen in the Lycurgus cup (a glass beaker in the British Museum). See below.

Multiple ultra thin layers of different metals (gold, silver, metal oxides, titanium, chromium, aluminum, zirconium, magnesium and silica) are vaporized by an electron beam in a vacuum chamber. The vapor 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.  The finished glass can have as many as 30-50 layers of these matirials yet the thickness of the total coating is approximately 30-50 millionths of an inch. 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.

Interesting tidbit: Dichroic glass does not have its own color; the colors that you see in a piece of dichroic jewelry come from the reflection and refraction of light, creating  an iridescent spectrum of color that is slightly different in every piece. As a result of its reflective and refractive nature, no two pieces will ever be the same.

Lycurgus Cup:  Late Roman, 4th century AD probably made in Rome

This extraordinary cup is the only complete example of a very special type of glass, known as dichroic, which changes colour when held up to the light. The opaque green cup turns to a glowing translucent red when light is shone through it. The glass contains tiny amounts of colloidal gold and silver, which give it these unusual optical properties. Photo from Bristish Museum.