24 янв 1884 г. - Carborundum is a very hard mixture consisting primarily of silicon carbide; it is used as an abrasive and, in powdered form, in a method of engraving invented by Henri Goetz. He used it to get a dotted effect by sprinkling it over a metal plate which was then pulled through a press, which got the grains to push into the metal.
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24 янв 1884 г.
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~ 141 г назад