The Determination of the Transformation Point of the Same Optical Glasses in Three Different Laboratories

JSGT 1934 V18 T079-T087

The transformation temperature of seven different optical glasses of very different composition and physical properties have been determined at Jena, at Berlin and at Sheffield, using in the first-named laboratory the thermal expansion method, and in the two others an electrical resistance method in different forms. The results are all in such good agreement as to indicate, in general, that the transformation point, when the glass is heated at a rate of approximately 4° per minute, can be determined with an error not exceeding ±5°.

E. Berger, M. Thomas & W. E. S. Turner