Depending on the nature of its additives, special glass is used to produce crystal, video screens or optical fibers. Fluorine and its derivatives Hydrofluoric acid and ammonium bifluoride serve to mat surfaces such as frosted light bulbs. With sulfuric acid, they are also used for the chemical polishing of cut crystal glass and some hollow glasses. Synthetic calcium fluoride is an opacifying agent for the milky or iridescent glass vials used in the perfume industry or as lamp stands. Sulfur hexafluoride, injected between two sheets of glass, reinforces the sound insulation of triple-glazed units.
Fluorine also plays a role in the composition of glass for optical fibers.
As network stabilizers, barium and strontium carbonates are used in the composition of high-quality technical glassware. Barium increases the refractive index, chemical resistance and hardness of the glass. It is also used to make glass for breakable phials and serves as a substitute for lead in crystal. Strontium is more widely used for color screens since it affords a better barrier to X-rays than barium and prevents glass from browning under the effects of ionizing rays. Updated August 10, 2001.