< RIGID REPRODUCTION MOULDS
REPRODUCTION MOULD CONSTRUCTION
As well as having a wide variety of moulding media to select from, foundry technicians can also choose to use a number of mould construction methods. The construction method and features seen in a given mould may depend upon it’s intended end use (ie for wax or resin casting), the moulding material used (rubber, plastic, other), and the personal preferences of the mouldmaker.
This next sections examine some of the basic mould types and construction techniques seen in art foundries and sculpture studios. When visiting foundries, do expect to see some variations to the descriptions given here, as each foundry tends to evolve it’s own particular methods to suit their individual work practices.
IMPRESSION MOULDS
Impression moulds are among the simplest of all moulds. Pressing a hard image into a soft material like clay leaves a negative impression which can be filled with a suitable casting medium, thus creating a positive copy. If the casting medium poured in is wax, this copy can later be used to produce a lost wax metal cast.
Clay is one suitable impression material, alginate and agar agar can also be used to good effect. There are a number of ‘wax like’ impression materials available from mouldmaking stockholders, these are usually plasticised by hand manipulation or warming in water baths prior to being impressed into the pattern and allowed to harden. As noted in the introductory page (ABOUT REPRODUCTION MOULDS), impression moulds are generally rather crude and somewhat limited for art foundry usage, although the technique is useful for demonstrating to students the basic principals of reproduction moulding and casting.
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