During the war raw materials became scarce, and research began to focus on alternatives. Polystyrene resins and nylon had already been used since the 1930s, and industry began to explore the possibilities of other forms man-made materials. A company called PPG industries created a new compound in 1940, which they called 39 – the 39^th attempt at this particular clear resin! During the War it was used in the Aviation industry for fuel tanks and clear fuel lines, but when peace arrived the company were left with about 38,000 pounds of excess product in liquid resin form. They began to experiment with uses for the material, and various companies took an interest due to its useful properties of high impact resistance and clarity. Lens manufacturers Essilor, Armorlite and Sola started making CR39 plastic lenses, and from the 1960s onwards  popularity has grown.

CR39 plastic is cast in a mould and then cured. The entire range of lens powers can be worked on CR39, and to make it completely user-friendly it’s mostly treated with a scratch resistant coating. Treat your plastic lenses with care and they’ll give you many years of service. Don’t lay them curve side down on any flat surfaces, wash them with warm soapy water before you polish them. Don’t put anything abrasive in the case with them! Next time you put your specs on and they give you crystal clear vision, take a moment to appreciate the history of a remarkable product that makes our lives so much better and safer today.