Abstract: This invention is directed to a glass frit composition essentially free from lead and cadmium exhibiting a linear coefficient of thermal expansion (25.degree. C.-300.degree. C.) between about 75-85.times.10.sup.-7 /.degree.C., good flow at temperatures between about 950.degree.-1000.degree. C., a softening point between about 650.degree.-725.degree. C., and excellent resistance to attack by alkaline detergent and hydrochloric acid, said frit consisting essentially, expressed in terms of weight percent on the oxide basis (except for the fluorine content), of______________________________________ SiO.sub.2 49-55 MgO 0-2 B.sub.2 O.sub.3 13-20 CaO 1-7 Al.sub.2 O.sub.3 4.5-7 SrO 0-8 Na.sub.2 O 5-8.5 BaO 0-11 K.sub.2 O 5-8.5 ZnO 0-2 Na.sub.2 O + K.sub.2 O 11-16 F 0.25-3.

Abstract: An electrical heating unit of the integral element type, comprising an electrical heating element indirectly bonded to a supporting beta quartz-zinc petalite glass-ceramic plate is described. A semicrystalline zinc aluminosilicate coating is provided between the glass-ceramic plate and the heating element, to improve the adherence and stabilize the resistance of the element and to protect the plate from deterioration during and subsequent to the bonding of the integral heating element to the unit.

Abstract: An electrical heating unit of the integral element type, comprising an electrical heating element indirectly bonded to a supporting lithium aluminosilicate glass-ceramic plate, is described. The glass-ceramic plate is provided with a semicrystalline zinc aluminosilicate coating which protects it from the harmful effects of interaction with subsequently applied ceramic and metallic compositions making up the heating element and associated components.