JULY, 1935
313
INTERESTING"SHORTS' ABOUTELECTRICAL INSULATION MATERIAL
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Images Were Kissed . . Mica Became "Insulation." Mica was used for many peculiar purposes before it became an electrical insulator. One of its mast interesting early applications as an "insulating material" was the glazing of Holy images. Images of the Holy Virgin were much kissed by devout Christians in the 17th and 18th Centuries. Wear and tear on the images were finally checked by glazing them with mica. Linseed-It's Food in Abyssinia It's hard to believe-what we use principally as a base od for paint and varnish. Abyssinian~use for food. But linseed and Linseed oil were used for foo many centuries before they found their way into the paint and varnish business. Boiled linseed oil in paints and varnishes acts as a vehicle to form the film. The oil itself is pressed from the seed of common flax, and heat is applied to increase the yield of oil. Bug Harvests . . . Twice a Year Plant lice and shellac-- they are part of the electrical industry. Shellac is used in some kinds of electrical insulating varnishes and it comes from bugs which feed an the sap of trees in India! These bugs or plant lice exude a resin that finally entombs them. Before the lice die their
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young are transplanted to other trees. The older generation and the resin it has produced is scraped from the trees. After much refining to separate resin and insect, the product is shellac of several grades. About six months are required for one crop of shellac. Yellow Gum from"Blue Earth." King Tut's sarcophagus was varnished withmelted amber. That was the hardest resin known then, and it still is. The ancient Phoenicians valued amber highly and braved the storms of the Atlantic in their triremes to gather it from the shores of the Baltic. The Baltic is still the greatest amber region of the world. On the shores of East Prussia it occurs in colored sand called "blue earth." Amber was one of the first resins used for insulating varnish, but because of its high cast it has been replaced by other materials. Copal -- Aged for a Million Years Vast tracts an the mainland coast of Zanzibar, once covered by primeval forests, now yield fossil copal or resin. Today not a single tree is visible along this coast, but a t a depth of about four feet are valuable deposits of copal. formed from trees that lived a million years ago. Masses weighing as much as five tons are sometimes unearthed in one piece. Copal resin is used extensively in varnishes and electrical insulating compounds.-- (From Westinghouse)
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