Granite as Insulator Material; granite chips used in manufacture of electrical insulators

Granite as Insulator Material.

The report of a committtee to the Franklin Institute on the use of granite as an insulator for electrical purposes has been published. Granite chips are calcined and powdered feldspar and kaolin added with water to make a plastic mixtured [sic] mixture and the molded objects heated to 3000 deg. F. and glazed. The product absorbed 0.76 per cent of water in a year. It crushed at 7000 pounds per square inch; and a sample of the size not stated had an insulation resistance of 8 megohms.