The Story of Glass

by Sara Ware Bassett

"No. Its diameter was fixed at the beginning by the wooden block. That settles its size once and for all; it is the length and thickness of the cylinder which are governed by the blower. Do you realize how strong a man has to be to wield such a weight as that lump of metal? It is no easy matter. Luckily he can suspend it against that wooden rest if he gets too tired. In England they use a sort of iron frame called an Iron Man to relieve the blower of the weight of the glass and the device was also used at one time in Belgium; but the Belgian workmen gradually did away with it."

For a long time the two children stood there fascinated by the skill of the blowers.

"Suppose we go on now and see the rest of the process," suggested Giusippe, a little unwillingly. "I could watch these men all day, but we have much to do, and if we do not hurry we shall not get through."

The next step in the work was opening out the cylinders, and this was done in two ways. The end of those made of thinner glass was put into the furnace while at the same time air was forced inside through the blow-pipe. As a result the air expanded by the heat of the fire, and burst open the cylinder at its hottest or weakest end. By placing this opening downward it was widened to the diameter necessary. The cylinders of thicker glass were opened by fastening to one end a lump of hot metal, thereby weakening them at this point. When the air was forced in by the blower it burst open the mass and the break thus made was enlarged by cutting it round with the scissors.

"Now come on, Jean, and see them flatten it out," said Giusippe.

Upon a wooden rest or chevalet the cylinder was now laid and detached from the pipe by placing a bit of cold steel against the part of the glass that still clung to the blow-pipe. At once the neck of the glass, which was hot, contracted at the touch of the cold metal and broke away from the pipe. The small end was then taken off by winding round it a thread of hot glass, and afterward applying cold iron or steel at any point the thread had covered.

"The cylinder is now finished at top and bottom and is ready to be split up the side," said Giusippe. "This they do with a rule and a diamond point mounted in a long handle. The diamond point is drawn along the inside of the cylinder and opens it out flat. If there are any imperfections in the glass the cutter plans to have them come as near the edge of this opening as possible so there will be little waste."

Jean nodded.

"Now, as you will see, the glass is ready for the flattener. First he warms it in the flue of his furnace and then, using his croppie or iron, he puts it on the flattening-stone; if you look carefully you will see that the top of this stone is covered with a large sheet of glass. In the heat of the furnace the cylinder with the split uppermost soon opens out and falls back in a wavy mass. See?"

Jean watched intently as the great roll of glass unfolded and spread into billows. The moment it was fairly open the flattener took his polissoir, a rod of iron with a block of wood at one end, and began smoothing out the uneven sheet of glass into a flat surface. At times he had to rub it with all his strength to straighten it. This done the flattening-stone was moved on wheels to a cooler part of the furnace and the sheet of glass upon it was transferred to a cooling-stone. When stiff enough it was taken off and placed either flat or on edge in a rack with other sheets.