Here at Forge we only use the very best materials to produce our sunglasses. Many of our sunglasses are fitted with premium-quality Zeiss® CR-39 lenses.
CR-39, or 'Allyl Diglycol Carbonate' (ADC), is a polymer commonly used in the manufacture of sunglass and eyeglass lenses. The abbreviation stands for "Columbia Resin #39", which was the 39th formula of a thermosetting plastic developed by the Colombia Resins project in 1940.
The first commercial use of CR-39 monomer was to help create glass-reinforced plastic fuel tanks for the B-17 bomber aircraft in World War II, reducing weight and increasing range of the bomber. After the War, the Armorlite Lens Company in California is credited with manufacturing the first CR-39 eyeglass lenses in 1947.
Although CR-39 is a type of polycarbonate, it should not be confused with the general term "polycarbonate".
CR-39 is transparent in the visible spectrum and is almost completely opaque in the ultraviolet range. It has high abrasion resistance, in fact the highest abrasion/scratch resistance of any uncoated optical plastic. This makes it absolutely ideal in its application as eyewear lenses.
CR-39 is also about half the weight of glass with an index of refraction only slightly lower than that of crown-glass, and its high Abbe number yields low chromatic aberration, altogether making it an advantageous material for eyeglasses and sunglasses.
A wide range of colours can be achieved by dying of the surface or the bulk of the material.
CR-39 is also resistant to most solvents and other chemicals, withstands ageing, and material fatigue. In some applications it can be made to withstand the small hot sparks from welding, something glass cannot do, and can be used continuously in temperatures up to 100 °C and up to one hour at 130 °C.
Please note: our Sunglasses and lenses, although built to be robust, are not designed or rated to be PPE, and we do not recommend using them for such purposes.