Glass Blowing and Stretching
In making sheet glass, a very large lump of molten glass is gathered on the rod as is shown at (a). This mass is rolled on an iron slab, expanded (b) by blowing down the pipe, and further manipulated by rolling on the slab, reheating at the mouth of the furnace, re-blowing, and allowing the soft mass to hang downward. if the glass is to be used for windows, the blower has a cave in the floor about 8 ft deep, and in this hole he works the glass until he has a cylinder (c), which he swings backward and forward, holding onto the pipe. The cylinder is then blown to a length from 4 to 8 ft, according to the size of the window desired. It becomes very thin and chills rapidly. The blower then takes a second lump of hot glass, pulls it out to a string, winds it around each end of the cylinder (d), and cracks both ends off. A piece of wet iron is next drawn along the cylinder in the direction of the its length, as indicated by the dotted lines in (d). A crack follows the wet iron, and the detached cylinder opens a little at the long crack (e). A slight reheating, and opening out in a flattening kiln, serves to convert the split cylinder into a sheet.