Re: How are the lens of glasses made?

This is not really my field, but I wear glasses: high density plastics are moulded into large blanks, or lens shaped disks. These are computer lathed and polished with ultra fine rubbing compounds that give the final desired curvatures and smoothness. Lenses for glasses are smaller than large blanks, and can allow several sets of lenses to be cut out from them. Also, the eyeglass industry is big and busy enough that smaller blanks are made just for the size of a single eye glass lense. These too can be reshaped and polished on computer controlled equipement that is often right at the outlet where you purchase your glasses. An excellent source of information is to go into such a store in a shopping mall near you, if available, and ask them to show you how it is done. Often lenses are lathed, polished and coated using special equipment right there before your eyes. Polishing a lens simply uses ultrafine particles in a watery paste to gradually and finely polish the surface to a nice smooth shine. If you ever have an old watch face that is plastic and has a lot of fine scratches that make it unusable, just mix up some chalk dust and some water and swirl it on the face with a small cotton rag. Keep it wet. Be patient. You will see many of the scratches can be removed this way. That is basically how lenses and mirrors are shaped and polished for telescopes too.