FSG is produced in a complex and oustanding process using a unique gravity bending method. Cut-to-size, drilled and edge-worked flat glass sheets are heated in a special tempering furnace to about 700°C and shaped after exiting the heating zone. They are then cooled rapidly by cold air blown onto the bent glass. This results in the two outer surfaces contracting and solidifying before the interior, which induces permanent compressive stresses into the surfaces of the glass, effectively increasing the strength of the glass and keeping it in the new shape. The interior of the glass naturally balances the compressive stress surface layers by being under tensile stress. These properties result in the increased strength and safe breakage characteristics of thermally toughened glass. When the central tensile section of the glass is ruptured, the stress is explosively released, producing the fracture characteristics of small, relatively harmless fragments.