A close up of the more traditional setup for making telescope mirrors. Here a plywood top is afixed to a 55 gallon steel drum filled 3/4 of the way with water. The Pyrex mirror can now be ground on top of a disk made of plaster and cermaic tiles called "the tool". # 60 grit and a bottle of water shown is the grinding medium. The mirror and tool sit upon a cloth that is dampened, and will stay put while the he two disks are rubbed together by hand.