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XTRUDED plastic threads are being used to make window screens which never need painting. They are said to cost about the same as copper screens. The following are on the list of strategic materials--for other reasons than their strange names: tragacanth, dragon's blood, abaca, kapok, karaya, sisal, henequen, damur, kauri, vetivert, ylangylang. Sugar-coated steel! Absolutely dry, pure corn sugar is blown on the inner surface of the ingot molds. When molten steel is poured in the molds splashed metal is prevented from solidifying on the sides of the mold, thereby producing a better surface on the steel. The sugar coating on the steel disappears in later processing, of course. Alloys obtained by addition of cadmium to copper are used in making trolley wire. They are said to have better electrical conductivity than the older, standard copper-tin alloys used for the same purpose. As an example of the work of microchemistry it was discovered in the Westinghouse Research Laboratories that tarnish film spots interfered with the operation of vacuum tube filaments. Analysis showed that bits of silica, or glass, from the tubes' bulbs had deposited on the filaments. This analysis called for the distillation of extra pure water, because the ordinary distilled water used in the laboratory had been kept in glass bottles and had dissolved enough silica to confuse the measurements of the silica in the film sample. This special water had to be stored in platinum bottles. From the same laboratories comes the report of a new material, "Prestite," which has released badly needed defense materials and provided a substitute which in a number of instances out performs the materials it displaces. Although Prestite is properly termed a new plastic because it is formed accurately to intricate shapes, it is actually a porcelain because it is made from
CHEMICAL EDUCATION
exactly the same ingredients as that product and is fired in the same kiln with it. Mechanically, the plastic is as strong in compressions as wet process porcelain. It retains its mechanical strength without deformation or warpage at temperatures that would completely destroy phenolic plastics. Electrically, the material is the equivalent of wet process porcelain. It has the same dielectric strength, is completely impervious to moisture, may be subjected to repetitive flashover without surface charring, and otherwise behaves like the highest grade of electrical porcelain. It has also replaced aluminum for use in water-cooler reservoirs. In recent months Americans have had the opportunity to see many of the finished weapons produced for national defense. The drab paints used in World War I appear bright and shiny alongside the lusterless enamels being used today. These enamels dry without gloss and have very poor photographic property. A lusterless blue enamel which is used over the olive drab for lettering tanks, trucks, and other equipment, shows less contrast than did the black enamel formerly used for lettering. Green cotton, said to yield 30 times as much wax as the ordinary white varieties, gives promise of becoming an important source of wax for polishes. Manufacturers of furniture polishes, floor polishes, auto polishes, and simiiar protective finishes requiring a wax with a high melting point would benefit chiefly from the use of the new material, especially in case of an acute shortage o f wax from the usual sources. Southern cotton fanners would find an always welcome new market. Because of metal shortages substitute materials are being earnestly sought by manufacturers of many metal articles. As an example of successful substitutions, experiments with glass kick plates for doors have been carried on. Kick plates made of ¼-inch Herculite polished plate glass have been found satisfactory.
