Abstract: A filter for molten metal having a high melting point is in the form of a net woven of glass yarns formed by twisting a multiplicity of glass fibers together. The glass fibers contain at least 75 wt. % of SiO.sub.2 and are thermally cured at a thermal shrinkage of 2.5 to 15%. The thermal shrinkage is expressed by (l-l')/.times.100 % wherein l is the length of the fiber before the thermal cure, and l' is the length of the fiber as thermally cured.

Abstract: A method for making a disposable model for a precision investment casting, which comprises casting a naphthalene or para-dichlorobenzene-containing modeling material into a pattern mold at a temperature of 150.degree. C or less, preferably 80 to 150.degree. C and further preferably at a casting speed of 5 to 0.1 kg/second; the modeling material being optionally admixed with a resin selected from the group consisting of polystyrene, polyethylene, polyvinyl acetate and a mixture thereof as a reinforcing material or comprising a mixture of naphthalene or paradichlorobenzene (preferably 80 to 30% by weight), a wax (preferably 20 to 70% by weight) and the resin as mentioned above (preferably 0.5 to 15% by weight on the basis of the whole weight of the modeling material).

Abstract: An investment casting method for making a desired casting of a relatively large size by the use of a mold of one-piece construction within close dimensions, which comprises preparing a thermally fusible pattern which is a replica of the desired casting, forming a refractory investment enveloping the thermally fusible pattern, melting the thermally fusible pattern out of the investment leaving a cavity in the refractory investment, and heating the investment to provide a rigid ceramic mold of one-piece construction. Melting of the thermally fusible pattern out of the investment is carried out in contact with a vaporized organic solvent without causing the thermally fusible pattern to thermally expand which may otherwise result in formation of cracks in the refractory, investment, that is, mold.