Evening Republican, Volume 21, Number 39, Rensselaer, Jasper County, 16 February 1917 — Welded Glass. [ARTICLE]

Welded Glass.

Welded glass suitable for certain optical instruments and other apparatus is a novel material, that is stated to be of great practical value as well as much interest.' As the welding procesft is described by Parker and Halladay to the Faraday society of London, the glass surfaces to be Joined are placed in good optical, contact under pressure, and are heated to a carefully predetermined temperature, which, to avoid distortion of optically worked surfaces, must not approach too near what is defined as the “annealing point.” This point of appreciable softening Is determined for any kind of glass by notlng the temperature at which the internal heat stresses-seen in (lie glass with polarized light quite suddenly disappears. Similar glasses unite perfectly well below this point; but with very unlike kinds, the softer becomes distorted before the harder is hot enough to make a good weld. _