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What is dichroic glass and why is it so special?
The definition of dichroic glass: 

The word "dichroic", pronounced Dye-Cro-Ick, is derived from two Greek roots, "di" for two and "chroma" for color. So "dichroic" literally means "two-colored."

You may hear dichroic glass referred to as "dichro" for short or even as "chameleon glass". You may also hear it incorrectly referred to as dichronic, dichrotic, dicroic, dicromic, diachronic, dichromatic and dichryllic just to name a few. Another misconception is that dichroic glass is the same as fused glass or refers to the entire fused glass movement. Though fused glass or warm glass may incorporate dichroic glass elements; doing so is not a requirement. Dichroic glass can be used as an element in glass blowing, bead making and of course glass fusing. 

The most distinctive feature of dichroic glass is that it seems to have more than one color, especially when viewed from different angles. For example, a particular formulation will appear blue, but shift the dichroic glass slightly and the color will transition to green. 

Dichroic glass viewed from two different angles and different lighting conditions
Dichroic glass viewed from two different angles and different lighting conditions

Here are some examples (not all) from Trezora's own collection of dichroic pendants and dichroic earrings.

A Brief History of Dichroic Glass
Where did dichroic glass come from:

The first and oldest man-made type of dichroic glass uses metals, such as gold and silver, that are evenly mixed throughout the glass to form a type of colloidal dispersion called a "solid sol". The metal particles are so small (5 - 200 nanometers) and so well dispersed throughout the glass, that on inspection, the glass appears completely homogeneous and monochromatic. A truly amazing example of this type of dichroic glass is the Lycurgus Cup. The Lycurgus Cup was created in the 4th century AD in Italy. In reflected light the glass appears green. In transmitted light the glass appears red.

Lycurgus Cup - example of dichroism
Dichroic effect in Lycurgus Cup (images courtesy of British Museum)

The second and more recent type of dichroic glass uses a vacuum deposition process to add layers of various metallic oxides on top of the glass. This is what most people think of as dichroic glass and the focus of our explanation since it is precisely this type of dichro used in Trezora's jewelry and art glass.

The history of this second type of dichroic glass goes back to the 1950's and 1960's when NASA, defense contractors and the Department of Defense developed this high-tech material for use as optical filters, as a shield against cosmic radiation and many other uses. For example, the golden sheen on an astronaut's face shield is a dichroic coating meant to protect against the harsh glare of natural and obviously unfiltered sunlight. 

Thin Film Physics and Manufacture of Dichroic Glass
Technical aspects and exploration of the physics of dichroic glass:

Dichroic glass does not use paints, dyes, gels or any standard coloring agents to create color anymore than a prism does. The fantastic colors are created through the manipulation of light. The multi-colored effect is the result of complex light interactions called "thin film physics". Thin-film physics are also responsible for rainbow patterns in a soap bubble, the swirling colors of an oil slick floating on a puddle and the dramatic reflections in dragonfly wings. 

Thin film physics in an oil slick rainbow
Thin film physics in an oil slick rainbow
Examples of thin film physics in an oil slick rainbow

Dichroic glass requires complex processes which have been mastered by a handful of manufacturers. The limited supply is partially due to the requirement for very high-tech equipment. Dichroic glass is created by vaporizing various metallic oxides in a vacuum chamber, using a high-voltage electron beam, and allowing the molecules to be deposited onto the surface of a blank sheet of usually clear or black glass. Careful control (using computers) of time and temperature determines the thickness of the oxide deposited on the glass. The complete process may require from 15 to 50 distinct layers (steps) of alternating metallic and silicon oxides. The total thickness of the oxide layers may total no more than 70 nanometers (700 angstroms). To put things in perspective, a human hair is 70 microns, or 1000 times thicker than the total oxide layer in dichroic glass. For further perspective, the wavelength of visible light ranges from 400 nanometers (the color violet), to 700 nanometers (the color red). The dichroic coating creates an optical filter that transmits (passes) certain wavelengths of light and reflects (blocks) others. 

The deposited oxides have no intrinsic color themselves, instead it is the physical properties of the metallic oxides in the dichroic glass that cause different wavelengths of light to either reflect or transmit more than others. These properties cause certain light waves to be reflected while others travel through the glass along slightly different paths thus causing the color shift we observe. Most dichroic glass uses both transmission and reflection of light to achieve the desired effect so that as you rotate a piece of dichroic glass, even slightly, you'll see shifting rainbow of colors. The physical properties that determine the final effect include the type of oxide (like silicon, titanium or magnesium), the number of oxides used, the order, number and thickness of layers, and the pattern (like hearts, dots, squares, etc.). With so many variables, dichroic glass presents an incredibly rich and varied palette of colors and patterns for glass artists to work with.

Adding to its complex optical properties, dichroic glass when fused as part of a glass object or piece of jewelry will change characteristics yet again with the new colors shifting towards the blue end of the spectrum.

The manufacture of dichroic glass is not a DIY project. The equipment and effort required to make dichroic glass is expensive meaning that a sheet of dichroic glass is itself expensive costing up to hundreds of dollars wholesale.

How to use dichroic glass in art glass and glass jewelry
How to make dichroic glass jewelry - The dichroic glass style guide: 

Dichroic glass adds flash and pizazz, it adds sparkle and intrigue, but too much can be overwhelming and gaudy. For example, subtle gold highlights throughout your house can create a sense of luxury and class. Now imagine every lighting fixture, plumbing fixture, wall and switch plate in gold and you get the idea. Stacking dichro on top of black glass is easy and can look good, but one can quickly transform a unique design into something you can find almost anywhere else. It is easy to fall into the trap of depending almost entirely on dichroic glass especially in glass jewelry. However; dichroic glass can never make up for a lack of design, quality, technique and artistic effort. Artists who explore the interplay of color between the broad color palette of art glass and dichroic glass will be richly rewarded with an incredible spectrum of possibilities. Making dichroic glass is rocket science, exploring its endless possibilities, that's art! 

Black and silver dichroic glass pendant Sculpted red dragon dichroic glass pendant

So, if you've never seen dichroic glass before, shop Trezora's collection of fine dichroic jewelry and discover an interplay of shimmering colors to suit your every desire. 

Science is beautiful! 

Additional Information on Dichroic Glass

1) Dichromagic - Austin Thin Films

2) CBS - Coatings By Sandberg

3) Navitar Coating Labs