GB579295A - An improved process for the manufacture of artificial porphyry or artificial granite - Google Patents

Abstract

A process for the production of tiles or moulded blocks of artificial porphyry or granite consists in separately preparing mortarlike lumps of at least two different colours by mixing sifted coloured cementitious materials with at least 30-40 per cent by volume of water, exposing the lumps to the air on a clean surface to eliminate surplus water, forcing them through screens to form granules, mixing the differently-coloured granules without crushing, cold-moulding under pressure, and permitting the moulded mass to harden after removal from the mould. The cementitious mixture consists of Portland or white cement or a mixture thereof, and powdered white marble or a coloured powder or a mixture thereof, with or without fillers. The coloured material may be grey limestone, a yellow metal oxide, terra cotta, red iron oxide, or green chromium oxide, while as fillers, crushed clay brick, kaolin, ground porcelain, or quartz sand may be used. The materials are passed through a screen of at least 900 meshes per square centimetre. After mixing with water and eliminating the surplus, the lumps are passed through a screen having square meshes measuring 4-8 mm. between the axes of the wires. The products are mixed according to the colour required and moulded under a pressure of at least 250 kg. per square centimetre. After removal from the mould, the blocks are hardened, in a room shaded from bright light and draughts, by standing in pools of water at a temperature of at least 25 DEG C. The outer surface is then removed to a depth of from 0.4 to 1 mm., and the tiles &c. are finally polished.