Patent ID: 7594529

Claim:
A method for the production of a shell mould, comprising: (i) dipping a preformed expendable pattern into a slurry of refractory particles and colloidal liquid binder whereby to form a coating layer on said pattern, (ii) depositing particles of refractory material onto said coating, and (iii) drying, steps (i) to (iii) being repeated as often as required to produce a shell mould having a primary coating layer and at least one secondary coating layer, wherein during at least one performance of step (ii) a gel-forming material is also deposited onto the coating layer formed in step (i), such that after contact with the coating layer, moisture is absorbed by the gel-forming material thereby causing gelation of the colloidal binder so reducing the time required for drying in step (iii), and wherein the gel-forming material is a super absorbent polymer.