WHAT IS A REPRODUCTION MOULD FOR LOST WAX CASTING?
The previous MASTER PATTERNS section described the two types of master pattern used in lost wax foundry casting – the LOST PATTERN, and the PERMANENT PATTERN. Unlike the lost pattern, if a permanent pattern is going to be used as the 'blueprint' for a casting, the founder must first create a REPRODUCTION MOULD from which a wax copy (the WAX PATTERN), can be made.
A reproduction mould is (at it's most simple), a negative impression of the sculptor’s original art work. Those parts of a design that are viewed as high points on the master pattern’s surface (a nose for example), translate as low points or 'impressions' in the reproduction mould; conversely, dips and depressions on the pattern’s surface translate as raised high points as viewed in the reproduction mould. In some respects the reproduction mould is somewhat similar in it's function to a photographic negative, both the negative plate and rubber mould can be considered intermediate vehicles which are used to transpose an ‘image’ from one medium to another.
In the art foundry, most reproduction moulds are used to create wax versions of sculptural designs for lost wax casting, though it is often just as easy to produce copies in other materials including plaster of Paris, resin and even low melting point metals like LEAD. In most cases it is possible to use the same reproduction mould to produce casts formed in a variety of materials.
TYPES OF REPRODUCTION MOULD
The simplest reproduction moulds are created by impressing a hard pattern surface into a soft material such as clay. This forms an imprint of the design in the clay, which can then be filled with wax or plaster - a crude, but occasionally effective moulding technique. This impression technique can be traced 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 mould makers are expected to accurately reproduce extremely complex and detailed forms.
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