Latex liquid rubber is an emulsion which will air-dry on the surface of a master pattern to form a thin peelable mould. Moulds made of latex have a comparatively long life are easily made and will give good definition and accuracy of reproduction. Masters can be made from a variety of materials including plaster clay wood and some non-porous materials. Thickener can be added to increase the viscosity of the latex to help a mould form on non-porous surfaces and reduce running. Dries to form a thin peelable mould.