ABSTRACT
Polished Plate Glass, after “casting” or “forming,” has its surfaces mechanically ground and polished. It is melted and refined in the same type of tank furnace as Sheet Glass, and the chemical composition is similar, except that for Polished Plate the materials are selected and refined. When it emerges from the lehr, the glass has rough, unattractive surfaces which must be removed by grinding and polishing to obtain the highly polished surfaces associated with Plate Glass. So from the lehr the ribbon of glass travels forward to the machine which grinds and polishes the surfaces simultaneously. This process of grinding and polishing both surfaces of a moving ribbon is the latest development in Plate Glass manufacture. Each grinding head above and below the ribbon has a vertical motor-driven spindle carrying a cast iron disc in which there are grooves to ensure even distribution of the sand and water.
