Glass Magazine - July/August 2010

Technology
Figure 2: A graphical representation of the differences between
the traditional rolling process and the microfloat process.

are released, and the glass is cooled even more at a slow, controlled rate. The glass is then cut into sheet sizes and is ready for ceramization, where it is transformed from a glass into a glass-ceramic.

Traditionally, the forming step of glass-ceramics manufacturing is accomplished by a continuous flow of molten glass out of the melt tank through a nozzle between rollers (see Figure 2). The distance between the rollers determines the thickness of the glass ribbon. This traditional rolling process results in surface imperfections in the finished glass-ceramic glazing product. Contact with the rollers leaves slight to moderate imprints in the finished glass surface, similar to the imprints in an orange peel. These slight surface imperfections cause distortion when looking through a finished window. The distorted glass-ceramic surface can be smoothed to remove the roller imprints, but only by an energy-intensive polishing process.

Traditional glass-ceramic manufacturing also requires that hazardous heavy metals — such as antimony, arsenic and barium — be added as refining agents in order to remove bubbles. Schott has developed alternative refining processes for Pyran Platinum glass-ceramic that do not require hazardous heavy metals. That means fewer heavy metals are ending up in landfills at the end

Resources

Pyran Platinum fire-rated glass-ceramic is available through distributors such as General Glass International, Secaucus, N.J.; Glassopolis, Toronto; Interedge Technologies, Sausalito, Calif.; and Safti First, San Francisco.

of a product’s life. And it means a
healthier environment for the people
who work around the microfloat tank
and the products that it creates.

The resulting Pyran Platinum glass-ceramic is fire-rated up to 90 minutes in windows and up to 180 minutes in doors, passes all required fire endurance and hose stream tests and is more environmentally friendly than traditional fire-rated glass-ceramics. It was recently granted “cradle-to-cradle” certification by MBDC, or McDonough Braun-gart Design Chemistry LLC, because of its material content, recyclability, and manufacturing characteristics. This certification qualifies products for a special credit in the Leadership in Energy and Environmental Design Green Building Rating System.