To endure the punishing heat and high compression of aviation engines and withstand the effects of lead in the gasoline, a new spark plug has been developed for the U. S. Air Forces. Its insulator is chemically akin to sapphires, rubies and oriental amethysts, and is harder than any substance save the diamond. The entire output of the new plug is going to the U. S. government for airplanes and tanks and to commercial airlines for use in transport planes. The basic material of the insulator is aluminum oxide, which is mixed with a binder, molded to shape and then baked in a high-heat kiln.