Did you know that there are multiple types of lens materials used on glasses of all types? Most people would give you a blank stare if asked about some of the names below. It's true; glass is not the only stuff in town.
In this article I will go over the most common materials used to make lenses, as well as the advantages each one offers. Who knows, you may just drop your current pair of shades in favor of something else.
Glass – Optical quality glass is free of distortion causing objects such as bubbles and / or seeds that plague other types of glass. Because of this, optical glass makes the clearest lenses available anywhere. While optical quality glass lenses may be heavier than plastic lenses, they are much more prone to survive heat damage. Also of interest is the fact that glass is much more scratch resistant than either of the two lens materials listed below.
CR-39 – Probably the best optical quality plastic, CR-39 is made from hard resin and is highly impact resistant – Much more than glass. If you need something extra light, CR-39 saves the day too; it weighs half as much as glass.
Polycarbonate – Polycarbonate is the strongest of all optical quality lens materials. Most ofen, you will see safety glasses, ballistics glasses, and high impact glasses being made from polycarbonate. Lenses made from polycarbonate are also the lightest – three times lighter than glass. Not everything is rosy though; polycarbonate lenses scratch easily, and must be hard coated to meet the scratch resistance that CR-39 plastic offers.
So which material is right for you? Most of the time, the type of lens you choose is a matter of comfort. If you need something light and strong, the obvious choice is either CR-39 or polycarbonate. If the ultimate in scratch resistance is what you are after, then get glass.
Either way, by properly educating yourself about the various advantages and disadvantages each material has, you can make an informed decision as to what you really need.