What makes “boro” difference from other glass? The key is it’s very low 33 coe (coefficient of thermal expansion). Boro’s coe is low to make it resistant to thermal shock, more so than any other common glass. It is less subject to thermal stress and is often used in bottles. You would know it best as Pyrex but other names are Simax, Borcam, borosil, suprax, Kimax, Heatex, Endural, Schott, Refmex or Kimble. When you think about why some glass can go from freezer to oven and back again and some can’t it is all about the coe.
Borosilicate is make with silica and boron trioxide as the main constituents. It is created by adding the boric oxide to the traditional glassmaker’s frit of silica sand, soda, and ground lime. Since boro melts at a higher temperature than ordinary silicate glass , new techniques were required for production. Borrowing from the welding trade, burners combining oxygen with natural gas are required. Softening point is 1510 F.
Borosilicate has many uses such as aquarium heaters, tobacco pipes, guitar slides, thermal insulation tiles (space shuttle) and much more.
However, for the purposes of this blog we will take about lampworking and beadmaking. In lampworking the glassworker uses a burner torch to melt and form glass using a variety of metal and graphite tools to shape it. It is referred to as “hard glass” and has a higher melting point of 3000 F, which is higher than “soft glass”, which is more preferred by beadmakers. The glass used in lampworking comes in glass rods for solid work and glass tubes for hollow work. Lampworking is used to make complex and custom scientific apparatus. Some labs have lampworking shops to manufacture and repair glassware. Lampworking is also done as art and common items made include goblets, paper weights, pipes, pendants and figurines.
Recently there has been an increase in the popularity of beadmaking. Borosilicate make by Northstar, Momka, Trautman and Glass Alchemy are the top manufacturers. The metals used to color boro glass, particularly silver, often create strikingly beautiful and unpredictable results when melted in an oxygen-gas torch flame. Because it is stronger and more shock-resistant than soft glass, boro is particularly suited for sculpting and creating large beads.
Some info from Wikipedia.