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WHAT IS A REPRODUCTION MOULD?
The first section of this website - MASTER PATTERNS described the two basic types of master pattern used in the art foundry – the LOST PATTERN, and the PERMANENT PATTERN. If a permanent pattern is going to be used for casting, it is first necessary to create a reproduction mould from which a wax copy (the WAX PATTERN), can be produced.
A reproduction mould is simply a negative impression of the sculptor’s artwork. Those parts of a design that are high points of form on the master pattern’s surface are later seen as low points in the reproduction mould; conversely, dips and depressions on the pattern’s surface are seen as raised high points when viewed in the reproduction mould. In some respects the reproduction mould is rather like a photographic negative, both the negative plate and rubber mould are intermediate vehicles, used to transpose an ‘image’ from one medium to another.
In an art foundry environment, most reproduction moulds are used to create wax versions of sculpures for lost wax casting. Of course, it is possible to produce copies moulded artwork in other materials, including plaster of Paris, resin, and even directly in low melting point metals. In most cases it is feasible to use the same reproduction mould to produce cast versions in different filler materials. Despite the versitility of most reproduction moulds, any artist intending to use a single mould for making versions of an artwork in different materials should inform the founder in advance. This information will enable a moulding technician to select the optimum moulding compound or adjust the mould’s design features.
TYPES OF REPRODUCTION MOULD
The simplest reproduction moulds are created by impressing a hard pattern image into a soft material such as clay. This leaves an imprint of the design in the clay, which can then be filled with wax or plaster. This is a crude, but effective moulding technique, best suited to forming low relief designs – though three dimensional images can be constructed by joining a several such impressions together. The impression technique can be traced at least to the cuniform seal makers of Mesopotamia, who were casting in lost wax some 5500 years ago [ref]. Of course the limitations of this impression technique are such, that is of little use in today’s founding environment where mouldmakers are expected to accurately reproduce extremely complex and detailed forms.
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