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PERMANENT PATTERNS
In contrast to LOST PATTERN casting, PERMANENT PATTERN casting (sometimes also called INDIRECT CASTING), offers sculptors and designers the freedom to use a wide range of modelling and construction materials for foundry PATTERNMAKING (including clay and plaster). This is possible due to the introduction of two intermediate stages into the casting process. The first of these stages is REPRODUCTION MOULDING, a general term that refers to rubber, plastic and plaster moulding materials, all of which can be used to create a [negative] image impression of the artist's origninal sculpture. The second additional stage is WAX PATTERNMAKING. Wax patternmaking is the process of forming and extracting a wax version of the artist’s original design from a reproduction mould. This reproducable wax pattern is then used for INVESTING instead of the artist’s original artwork, allowing the artist’s original artwork to be kept intact throughout the whole casting cycle, hence the name PERMANENT PATTERN (or 'plâtres de travail' [Fr]) .
These additional two stages have a number of implications. The sculptor can now use any stable material to create their lost wax process master pattern – clay, plaster, metal, ceramic and so on. Even if a soft material like wax is used for the pattern, this pattern will be kept intact because all the versions used for casting can be extracted from a reproduction mould – not the artist’s original model. The existance of a reproduction mould also allows the founder to accurately reproduce multiple copies of the artist’s design, this means that if the casting process fails at any point, the founder will be able to make a second or third wax pattern with relative ease and without the artist having to re-model their original work. An added advantage is that the founder will also be able to produce multiple casts of the same sculpture at the artist’s request, this is known as casting an EDITION.
Nowadays, nearly all artist’s patterns sent to professional art foundries for lost wax casting are treated as permanent patterns. Although casting errors are rare, very few sculptors are willing to risk the loss of their work for the relatively small cost of making a reproduction mould – in this respect most artists consider a rubber reprodcution mould of their original artwork to be a form of insurance. Founders also prefer permanent patterns – processing and casting the work is an altogether less nervous affair and waxes of a predictable wall thickness can be easily produced from rubber moulds. Equally important is the ability to retain the original sculpture as a quality control reference throughout the entire casting cycle, especially at the CHASING or finishing stages.
CLAY & CERAMIC PATTERNS > |
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