Abstract: A coil has one or more layers of primary and secondary windings about a bore liner, with the primary and secondary windings separated by a winding of glass threads. The coil is heated in an oven to first drive off the volatiles of the binder forming part of the ceramic insulation for the primary and secondary coils and which volatiles pass through the winding of glass thread. The coil is further heated so that portions of the glass fibers forming the threads vitrify with the non-vitrified remaining portions retaining their well-defined, discrete fiber characteristics, whereby they extend through the vitrified glass to seal the coil, reinforce the coil against vibration and shock, and enable a dimensionally compact coil.

Abstract: A method contemplated by the present invention for producing semi-finished prosthetic dental preforms essentially comprises the steps of repulverizing a dental porcelain mixture including a suitable binder by spray drying such dental porcelain molding the repulverized dental porcelain mixture in a die member having a cavity with a form generally complementary to that desired for the molded product, removing the molded product from the mold; and applying an outer coating of a suitable second dental porcelain to selected exterior surfaces of the molded product. The binder for the ceramic material comprises 10.5% to 8.5% ethylene vinyl acetate resin, 5.3% to 3.9% mineral seal oil and about 2.2% to 1.6% stearic acid.