What applications require the various lens materials, and to what maximum temperature can each be subjected?
Lens materials include Instrument Glass, Laminated Safety Glass, Tempered Glass, and plastic. Glass lenses are used for abrasion, chemical and wear resistant properties. Laminated safety glass reduces the possibility of shattering if the bourdon tube ruptures. Tempered glass is 2 to 5 times stronger the plain glass. Plastic lenses are used for impact, corrosion and chemical resistance. Special attention should be paid to the temperature and corrosive environments. Polycarbonate is selected for its superior impact resistance, Plexiglass for its clarity and scratch resistance and Homalite for is superior chemical resistance. In general, gauges with plastic lenses should remain below 140° F.
