ERAhUCS. in some applications competitive with plastics. possess properties not equalled now nor in the probable future by plastics. Ceramics. as inorganic materials, arc fundamentally more temperature resistant than plastics, which arc organic. Surface hardness and low water absorption arc other great advantages of most ceramics which at least up to now have not been approached by the chemist's synthetic plastics. One of the oldest of the industrial arts, the ceramics industry nevertheless maintains a youthful attitude toward the need for continual alertness and adaptability. Dr. G. H. McIntyre, research director of the Ferro-Enamel Corporation, in a recent talk before the American Ceramic Society, reviewed some of the industry's future requirements and present accomplishments, including corrosion-resistant porcelain enamel as a replacement for special high-cost alloys and semidull porcelain enamel finishes for which a great architectural demand is foreseen. In the glass industry, largest of ceramic industries, recent developments include glass lighter than cork, prepared by heating to softness glass containing gas-evolving substances; microscopically thin glass fibers, useful as textiles or as insulating "wool"; nonreftecting glasses, made by coating the glass surface with an extremely thin film; and glass plumbing which, using special burners, can be as easily joined as common iron tubing. All of these developments have important war applications, either as replacements or as fundamentally new materials, for one virtue of the ceramics industry is that its products are in general available even during wartime. One of the ceramic industry's adaptations to present demand is the Multiform process, developed to supply glass electric insulators in shapes which could not hitherto be manufactured eco-
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llomically Oil a largl' ~alc. The process. developed by Corning Glass \Vorks, involves a combination of cold-molding glass batch material and subsequent fusing. Products already availabit' cover a broad line of electrical parts, such as tube socket bases, switch cups, condenser spacers, crystal holders, and so on. Many other applications can be foreseen; however, present wartime need for insulating parts will emphasize this application. The characteristics of parts made by the Multiform process compare well wit.h parts made by conventional glassmanufacturing means, although not quite so good. Many kinds of special glasses mOlded by the Mult.iform process are available for electric parts and in many respects have unique properties as compared with other ceramic products. A relatively new type of glass which is almost pure silica has extremely low thennal expansion, while glasses of the borosilicate type compare favorably with electrical porcelains in this respect. Electrical glasses are particularly outstanding with respect to the voltage which they will withstand and t.heir low dielectric loss at extremely high frequencies. The main limitation of glass as COIUpared with other ceramic insulators is that even the best temperature-resistant glasses cannot be used at temperatures above lSOOoF. The cost of parts made by the Multiform process is said to be compelitive with that of other high-grade ceramic insulators. For the manufaCLUre of thin-walled articles and hollow cylindrical shapes traditional Ca'itillg techniques will probably be preferred, but for plates, rods, discs, beads, bushings, and articles of more intricate shapes requiring close tolerances the Multiform pressing method seems particularly applicable.-Industrial
Bulletin. of Arthur D, Little,
!tIC.
