Dichroic (pronounced dye-crow-ick) glass, dichro for short, means ”two colored.” The word comes from the Greek words ”di” for two, and ”chroma” for color. It was named that because, when you look at this glass, it appears to have more than one color at the same time.
What’s the difference between dichro and fusion glass?
There is a bit of confusion in glass circles about the difference between fused glass and dichroic glass. All fused glass is glass which has been submitted to the process of using a kiln to melt assorted pieces into a single unified piece of glass. Fusion glass is a single layer of glass, created to melt perfectly with other glass that has the same coefficient of expansion.
Dichroic glass is fusion glass, but a very specific type. Dichroic Glass is specially created using a multi-layer coating placed on glass by a highly technical vacuum deposit process. Usually, the background of this coated glass is black or clear. It’s main characteristic is that it has both a transmitted color and a completely different reflected color.
The transmitted color is the color you see when you actually look through the glass, while the reflected color is the color you see when you hold the glass at an angle. (It will be the opposite color of the transmission.) In dichroic glass, these two colors shift back and forth depending on the angle from which you view it.
Where did dichroic glass come from?
In the 1990’s, NASA began experimenting with treated glass for use in the space industry. Some say the experiments were conducted to find the “perfect” materials for space helmet face plates, and others say they were making satellite mirrors. Everyone agrees it was created for the space industry.
NASA placed various materials in a vacuum chamber and injected a fine mist of metal oxides inside. This deposited very thin layers of the metal onto the objects, producing the first dichroic glass. This glass was then applied to a variety of objects like face plates, satellite mirrors, re-entry tiles on space shuttles and specialized instruments.
Why it’s so special The various colors have as many as 45 layers of metals, yet the thickness of the total coating is less than a human hair! The surface has a reflective property known as thin-film physics, which is the same process that produces swirling rainbow patterns in a soap bubble, or a puddle of oil on water. It’s even the reason for the shimmer of dragonfly wings.
After fusing dichroic glass, it’s color generally shifts towards the left on the color wheel. Many other factors influence this color shift: the thickness of the dichroic coating, the time and temperature used for firing, the specific kiln used and the number of firings.
Other determining factors include the specific oxides sprayed on in the creation of dichro, and the type of base glass used. Some of the metals used in this process include: titanium, chromium, gold, zirconium, and aluminum.
Now it’s an artist’s dream
Of course, when glass manufacturers saw the beauty of this new glass, they immediately recognized how popular it would be with glass artists. However, due to the expensive equipment used in creating it, and the ultra-clean environment needed to create it, only a handful of companies actually began to produce dichro for commercial use. As a result, dichroic glass remains more expensive than other fusion glasses.
Dichroic Glass is specifically designed to be hot-worked, but it can also be used in its raw form for traditional stained glass projects. However, the thin film coating can be easily scratched or destroyed by the corrosive effects of flux or patina, so the dichroic layer must be protected. Contact paper works well to temporarily protect the dichro. A more permanent protection would be to fuse clear glass on top of it before incorporating it into a piece.
Try it – you’ll like it!
If you are a glass or jewelry artist, I highly recommend you try using dichroic glass in your work. Dichro has a beautiful shimmering effect similar to an opal, but it is much more durable than those soft stones. It makes a wonderful accent for stained glass work (we often use it to make eyes) and is perfect for fusion pieces as well.
Your local glass dealer should have samples to show you, and many studios sell “scrap packs,” which include a variety of different dichro glasses perfect for jewelry work.