Radiant electric heater

A radiant electric heater comprising a metal dish containing a base layer of thermal and electrical insulation material, a metal heat shield interposed between said insulation material and said metal dish and a resistance heating element physically supported by said insulation material, said insulation material comprising a deposited porous solid mass formed with a non-gaseous surfactant type foaming agent wherein said porous solid mass has non-porous fused silica particulates having an average particle size up to about 100 mesh United States screen size and with the porous characteristic being formed by void spaces between the deposited fused silica particulates, and with said solid porous mass of fused silica particulates having been formed by first depositing a foamed liquid suspension of the fused silica particulates and foaming agent in the metal dish then converting the deposited liquid suspension in situ to a gel condition and thereafter removing liquid from the converted gel mass of fused silica particulates.

A radiant electric heater comprising a metal dish containing a base layer of thermal and electrical insulation material having an integral upward extending rim, a metal heat shield interposed between said insulation material and said metal dish, and a resistance heating element physically supported by said insulation base layer, said insulation material comprising a deposited porous solid foam mass formed with a non-gaseous organic surfactant foaming agent, wherein said porous mass has non-porous fused silica particulates having an average particle size up to about 100 mesh United States screen size and with the porous characteristic being formed by void spaces between the deposited fused silica particulates, and with said solid porous mass of fused silica particulates having been formed by first depositing a foamed aqueous suspension of the fused silica particulates and organic surfactant foaming agent in the metal dish then freezing the deposited liquid suspension in situ to produce a gel condition therein and thereafter heat drying the frozen liquid mass at an elevated temperature until water has been removed therefrom.