Recent Developments in Optical Glass Manufacture

JSGT 1931 V15 T306-T320

 The paper traces the advances which have been made, principally in the post-War period, in the production of the various new types of optical glass used in the modern photographic lens. An account is given of the contribution of modern research to improved methods of manufacture as regards excellence of homogeneity of the glass, and also as regards its transparency to light. The latter property is largely dependent on obtaining the glass as free as possible from contamination with iron oxide, and the fact that modern British optical glasses are now made of a higher transparency to visible light than any material of foreign origin is due, not only to careful selection of raw materials, but also to the modern development of suitable clays for making the pot in which the melting process takes place.

Figures are given showing the improvements which have been effected in the transparency of borosilicate crowns and the usual flint glasses and also of the dense barium crowns. Reference is made to the present state of our knowledge on annealing, the improvements in the methods of testing the resistance of polished glass surfaces to atmospheric attack, and to the modern production of certain standard types of optical glass in the form of blown sheets.

W. M. Hampton & W. N. Wheat