Plate glass is cast by pouring it from a large pot on to a flat iron
table with a ridge all round it, and on which an iron roller is so
placed that when the molten glass flows on the table it passes over
and flattens it out to the required thinness, which is regulated by
elevating or depressing the ridges at the sides of the table, made
moveable for that purpose (the process is illustrated by the cut at
the head of this article). When cold, the surface of the plate is
ground perfectly flat and even by means of emery-powder (fig. 6), and
then polished with a cloth rubber charged with a fine red oxide of
iron called “crocus” (fig. 7). The grinding and polishing are both
performed by steam machinery.