Custom Tempered Optics

Tempered or toughened glass has been processed by controlled thermal or chemical treatments to increase its strength, both physically and thermally when compared to normal glass. Tempered glass is made by processes which creates balanced internal stresses. The greater contraction of the inner layer during tempering induces compressive stresses in the surface of the glass balanced by tensile stressed in the body of the glass. A strain pattern can be viewed from tempering when observed with polarized light or by using a pair of polarizing sun glasses. Sterling has perfected the “Maltese Cross Strain Pattern” which indicates a very hard temper with compressive stress exceeding 100MPa. This tempering formula is used for heat absorbing filters that experience extreme heating and cooling fluctuations.
Sterling is unique in that we have an in-house Tempering Department. Since the 1950’s Sterling has gained national and international recognition for tempering both large and small optical components. Sterling has been successful in tempering Optical Filters as thin as 1mm. We have six tempering and sagging ovens in our Tempering Department. By far the most common optical component that requires tempering is a Heat Absorbing Filter.