8 oz. Black Furnace Cement. A pre-mixed, creamy smooth black silicate ceramic type cement that is durable as firebrick when heat cured. It withstands temperatures up to 1,093 °C (2,000 °F). This easy-to-use cement is ideal for sealing metal-to-metal and metal-to-masonry joints under 1/8 inch. It spreads easily and bonds securely, preventing air and gas leaks in flue and chimney joints. Suitable for use on cast iron, steel, or firebrick, it is a reliable choice for installing or resetting furnaces or oil burners.