The grinder that is used to grind the lenses to the specifications of the prescription is called an edger. There is a constant source of water running over the lens while it is being ground in order to reduce the heat caused by friction on the glass. The friction heat can cause glass to crack or break. Water also makes the grinding easier and smoother on the edge and prevents scratching of the surface from dry glass grit.When the grinding is completed and the lenses are cleaned, tint is added to the lens by dipping the lens in a tint solution which is absorbed into the lens. The longer it is dipped, the darker the tint. The lenses are thoroughly rinsed and dried then are fit into the sunglasses frame and the frame is secured tightly around the lens by tightening the screws on the frame. Sunglasses frames are mass-produced from products like plastic, nylon, carbon fiber and metal.The process of making sunglasses has come a long way from when Roman Emperor Nero held polished light emerald glass gems up to his eyes and Chinese attached ceramic weights to the ends of ribbons draped over the ears in order to keep on their cool sunglasses.Looking for some new designer sunglasses? Check out Cheap Designer Sunglasses at http://sunglasses.supashops.com and grab yourself a bargain.