Abstract: A used foundry sand, especially one which has been bonded using sodium silicate binder, is reclaimed by agitating the sand with water in a plenum chamber having a suspended floor comprising a porous membrane, stopping the agitation and allowing the solids to settle on the floor. The water passes through and the sand settles on the floor, and the finer particles may then be removed e.g. by air elutriation. Preferably the water mixed with the sand has a pH below 10 and contains a flocculant, and the water recovered from the vessel has suspended solids content below 500 mg/liter.

Abstract: A riser sleeve has at its end which is uppermost when the sleeve is located in the mould a holding member which can be engaged by a mechanical holding device so as to adapt the sleeve to automatic handling. The holding member may be for example a disc, ring or solid or hollow cylinder and may be formed integrally with the sleeve or formed separately and fixed to the sleeve. By adopting a standard shape and size for the holding member for a wide range of sleeve shapes and sizes the same holding device can be used to handle the whole range of sleeves.

Abstract: A thin shell ceramic mould for use in metal casting is formed by applying a thin coating of a suitable material and binder to an expandable pattern, e.g. expanded polystyrene, having a density of about 30 to 50 kg/cu.m. The coated pattern is subjected to heat at a temperature of about 1000.degree. C. for 10 minutes to burn out the pattern and cure the coating. The ceramic shell is made just thick enough to be handled.

Abstract: A method of casting a metal article in a mould box comprises locating an expendable pattern in the box, the pattern having a gas permeable refractory coating thereon, placing and compacting unbonded particulate material about the pattern and supplying molten metal into the box so as to vaporize or burn away the pattern and form the article of defined shaped while applying a vacuum during casting. According to this invention, the method is improved by compacting the particulate material to a maximum bulk density where it contacts the coated pattern and applying a vacuum to the compacted particulate material so as to create sufficient pressure gradient in the height of the compacted material to maintain the integrity of the gas permeable refractory coating. In this way, the risk of mould collapse, metal breakout, and pollution are reduced.