The Preparation of the British Model of Standard Strain Discs

JSGT 1945 V29 T148-T169

The apparatus employed in the preparation of discs of glass strained to a precisely-controlled degree, and the equipment necessary for their calibration are described in detail. The general principles used as basis were those adopted earlier by the Glass Container Association of America. The discs were 3½ inches in diameter. The standard of strain adopted was a retardation of 22·8 µm measured at points one-quarter of an inch from the edge. Discs of sub-standard strain were also prepared.

A. J. Holland