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  Borosilicate (hard glass) is a boron based glass and is called hard because it has a higher melting temperature, does not hold heat very long, has a short working time when removed from the flame and is stiffer than soft glass. Glass Alchemy, Northstar, Colormax, Momka, Duran and Pyrex are all hard glasses.What is Borosilicate Glass? 
Borosilicate glass is a very unique and specialized variety of glass. Its composition is different from the "soft" glass that is normally used for beads, paperweights, art glass bowls, ornaments, etc. Borosilicate glass is far stronger than "soft" glass and has been used for everything from stovetop cookware to nuclear waste containment. One of its most frequent uses is to make scientific glassware such as beakers and test tubes.  
 
Chemical Composition  
Chemically speaking, borosilicate glass substitutes boron oxide particles in place of the soda and lime particles found in soft glass. The boron oxide serves as a flux or glue to hold the silicate particles together with aluminum oxide and sodium oxide. Because the boron oxide particles are so small, the silicate is held together more closely resulting in a much stronger glass. Borosilicate glass is also highly resistant to the strongest of chemicals and acid compounds. 
 
Unusual Durability!  
One big reason we prefer to work with borosilicate glass is because it results in a much stronger finished piece. It will stand up to a lot of wear and tear without having to treat it as carefully as soft glass jewelry. It often amazes people how many "accidents" this glass can survive without breaking or cracking. Unlike soft glass, Borosilicate glass is also immune to the corrosive (etching) effects of natural fatty acids found on human skin and the Alphahydroxy acids found in many skin care lotions and treatments currently on the market. 
 
Unique Color Palette  
Another major reason for using borosilicate glass is the amazing color palette available. There are actually fewer colors available to work with but each one is an organic, living color that can be manipulated and shaded with careful torch work and annealing. The finished piece appears much more dynamic and vibrant. Also, because of the chemical composition of borosilicate glass, different precious metals such as silver and gold may be used to color the glass in some very unique and amazing ways. 

"Dichroic Glass" is somewhat of a misnomer, since the dielectric coating that produces all the interesting colors is not glass at all, but a group of very thin layers of metal oxides. This stack of thin layers has a total thickness of three to five millionths of an inch. The layers produce an "interference filter", creating the varied and unique color characteristics we see. Since the filter is so thin, it has very little mechanical integrity of its own, and must be supported on a mechanically stable substrate. Glass is the ideal candidate for this substrate. Transparent, rigid and stable, it withstands high temperatures, and is not affected by moisture, solvents or most acids. The filter materials are actually more chemically stable than most glasses used as the substrate. Thus, what we commonly call "Dichroic Glass", is actually a piece of dielectric interference filter attached to the surface of a piece of glass. 
 
Dichroic is defined as the property of having more than one color, especially when viewed from different angles. Dichroic glass is a high-tech spin-off of the space industry. Thin layers of metallic oxides, such as titanium, silicon, and magnesium are deposited upon the surface of the glass in a high temperature, vacuum furnace.

The glass to be coated is carefully cleaned, and fastened to a planetary arm in the top of the furnace chamber. The oxides are placed in a crucible on the bottom of the chamber. Air inside of the chamber is removed with a high vacuum-producing cyropump, and the chamber is heated to 300oF. The metallic oxides are vaporized by an electron beam, and the rotating glass target is evenly coated with many thin layers. The resulting color is determined by the individual oxide compositions.

Dichroic coatings transmit certain wavelengths of light, while reflecting others, thus creating an interference-effect similar to the iridescence observed in Nature's fire opal, dragonfly wings and hummingbird feathers. The transmitted color is different than the reflected color, and a third color is produced by viewing the dichroic piece at a 45o angle. The resulting colors are pure, saturated, single wavelengths of light, that appear to originate from within the dichroic piece.

 
   
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