CHAPTER X.

SHEET AND CROWN GLASS.

Comparison of sheet with polished plate--Raw materials for sheet--Furnaces: various forms of tank furnaces-- Blowing process--Gathering, forming the gathering on blocks, forming the shoulder of the cylinder, blowing the cylinder, opening the end of the cylinder, detaching cylinder from pipe--Cutting off the “cap”--Splitting the cylinder--Flattening and annealing--Cutting and sorting sheet-glass--Defects of sheet-glass--Variations of the process--Attempts to produce “sheet” glass by rolling--Sievert’s process--Direct drawing processes-- The American process for drawing cylinders--Fourcault’s processes--Difficulties and limitations--Crown glass-- The blowing process--Limitations _p._ 149