What is dichroic glass? The term dichroic, meaning two colors, refers to any optical device which can split a beam of light into two beams with differing wavelengths resulting in the appearance of two colors. When talking about dichroic glass it refers to a thin coating that has been permanently adhered to the surface of glass, that gives the glass color changing properties. Examples of adding metals to alter the color of glass date back to the 4^th century and the ancient Romans. Reflective gold and silver particles were added to glass to give it color changing properties. Today we have NASA to thank for our modern dichroic glass. Their research and development of dichroic filters in the 1950s and 60s gave us the process used to create dichroic art glass. This coating process takes place in a vacuum chamber where quartz and metal oxides are vaporized with an electron beam. Resulting in micro thin layers of vaporized metals condensing on the surface of the glass and forming a crystal structure. This coating gives the glass its changing color appearance.