The Heat Expansion of Soda-lime Glasses

JSGT_1919_V03_T238_T242 (5 pages)

The amount by which a piece of glass undergoes expansion when subjected to heat is a matter of first-rate importance in practically all branches of the glass industry. In the case of lampblown apparatus, junctions are not easy to make if the two glasses concerned have very different rates of expansion when heated. When, as is the case in the electric lamp-making industry, the sealing, not only of glass to glass, but also of metallic wire into glass, comes into consideration, the difficulty may be still greater. In the manufacture of sheet glass strengthened by encased wire mesh, fracture may arise during its preparation, due to difference of expansion between the metal and the glass. Further, in the artistic branch of the glass industry, the flashing or casing of one glass by another ruby or blue on flint, or opal on flint, for example, depends for its success on obtaining two glasses with rates of expansion not far removed from one another. Otherwise the finished article will be split when subjected to the slightest action of a cutting tool.

S. English & W. E. S. Turner