Abstract: A vitreous ceramic composition for coating ceramic articles with a zinc and alumina base capable of separating rapidly up to 50% of crystalline phase consisting essentially of gahnite. The percentages by weight of the principal ingredients of the composition are the following. SiO.sub.2 30-50%; Al.sub.2 O.sub.3 10-25%; ZnO 8-25%; B.sub.2 O.sub.3 5-20%; TiO.sub.2 0-7%; other selected oxides can be added to change the fusability characteristics and heat expansion coefficients on the basis of specific applications of the composition.

Abstract: Vitreous ceramic composition belonging to the SiO.sub.2 -Al.sub.2 O.sub.3 -LiO.sub.2 -TiO.sub.2 system in which the components are selected in ranges of definite percentages with the addition of elements exercising a given nucleating effect of promotion of growth of polycrystalline phases and designed to be used as a coating composition to be deposited directly in dry granular form on incandescent supports for producing ceramic with high crystallization speed.

Abstract: The process provides for the firing in a furnace of ceramic bodies and their coating in an incandescent state on one face with dry granular or powdered glaze when all firing reactions of the ceramic bodies have substantially reached completion; a subsequent thermal treatment fires the glaze and gradually cools the tile.The apparatus for carrying out the process provides for a furnace for firing ceramic bodies, the furnace being divided into two section between which is a device for distributing glaze over the ceramic bodies conveyed to pass through the furnace.

Abstract: An apparatus for applying glaze, in the form of granules, to hot tiles, having a dispenser including at least an inclined surface with a pouring edge for cascade or curtain coating of the glaze onto the hot tiles brought below it, preferably conveyed on rollers. Provision is preferably made for successive pouring edges aligned transversally to the tile conveyor system, and respective inclined surfaces, in particular, in the form of rotating wheels, which are internally traversed by cooling liquid.