Abstract: A method of modifying a surface of a casting involves providing a casting mould; placing a perforated mask with the mould to define a masked area of the mould; spray-coating the masked area of the mould with a coating material selected for forming a surface layer on the casting; introducing a liquid casting material to the mould; and, solidifying the liquid casting material to form a surface modified casting. The present method reduces the tendency for the coating material to spall from the mould and permits the formation of thicker coating layers on the mould. Thicker and better quality surface layers may be formed on castings.

Abstract: A ceramic mould slurry is disclosed for forming moulds and metal castings of improved surface quality. The slurry comprises a binder, a gelling agent, a first refractory material having a density of &rgr;1 and a mean particle size of &agr;1, and a second refractory material having a density of &rgr;2 and a mean particle size of &agr;2, wherein &rgr;1>&rgr;2 and &agr;1<&agr;2. The denser refractory material migrates downward through the slurry toward the upward-facing mould surface, thereby allowing formation of a smooth and accurate surface.

Abstract: A ceramic mould slurry is disclosed for forming moulds and metal castings of improved surface quality. The slurry comprises a binder, a gelling agent, a first refractory material having a density of &rgr;1 and a mean particle size of &agr;1, and a second refractory material having a density of &rgr;2 and a mean particle size of &agr;2, wherein &rgr;1>&rgr;2 and &agr;1<&agr;2. The denser refractory material migrates downward through the slurry toward the upward-facing mould surface, thereby allowing formation of a smooth and accurate surface.

Abstract: A method of making a mold directly from the object to be molded is disclosed. The object is placed within a walled enclosure having a closed bottom and open top. A plurality of elongated metal rod elements is vertically introduced and packed into the enclosure in vertical contact with said object and side by side contact with one another. An infiltration agent, such as a liquid resin or metal, is introduced over the elongated metal rod elements and allow to permeate into the spaces between the rod elements. The mass consisting of the liquid infiltration agent and the elongated metal elements is allowed to solidify into a mold which is removed from the object.

Abstract: A method of making a mould directly from the object to be moulded is disclosed. The object is placed within a walled enclosure having a closed bottom and open top. A plurality of elongated metal rod elements is vertically introduced and packed into the enclosure in vertical contact with said object and side by side contact with one another. An infiltration agent, such as a liquid resin or metal, is introduced over the elongated metal rod elements and allow to permeate into the spaces between the rod elements. The mass consisting of the liquid infiltration agent and the elongated metal elements is allowed to solidify into a mould which is removed from the object.