This helps minimize some of the thermal disturbances caused by people in the room. A couple of the more active and generous graduates have even refigured mirrors sent to us by other amateurs in the area. Grinding proceeds on the familiar barrel top arrangement. Cleats spaced for different diameter blanks fit on any barrel. A photo-negative table and eye loupe are very useful when looking for pits during grinding.
Abrasives are to some extent a matter of preference.
Lab users supply their own while the class members use Willmann-Bell kits. The kits are used as a matter of convenience, although their price has grown since our first class. Experiments with different abrasives have ended in some debate, but some ideas are generally agreed upon. For example, many of us feel that 320 and 500 grit silicon carbide sometimes produce excess fracturing and pitting problems. Most prefer to use Aluminum Oxide if possible.