< MATERIALS FOR LOST PATTERNS
PERMANENT PATTERNS
In contrast to the LOST PATTERN technique, PERMANENT PATTERN casting (sometimes called INDIRECT CASTING), offers the sculptor the freedom to choose from a wide range of modelling and construction materials for patternmaking. This is made possible by introducing two additional stages into the foundry process. The first of these stages is REPRODUCTION MOULDING, a catch-all term that includes the use of 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 creating and extracting a wax version of the artist’s sculpture from the reproduction mould. The wax pattern is then used for INVESTING instead of the artist’s original artwork, this allows the artist’s original artwork to be kept intact throughout the whole casting cycle, hence the name PERMANENT PATTERN (or 'plâtres de travail' [Fr] - literally 'working plasters' [for casting]) .
These additional two stages have a number of important implications. Firstly, the sculptor can now use any stable material to create their sculpture master pattern – clay, plaster, metal, ceramic and so on. Even if a soft material such as wax is used to make the pattern, the pattern will still be kept intact, because all the copies used for making a casting will be extracted from a reproduction mould – not the artist’s original model. The reproduction mould also enables 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 restart the process without the artist having to re-model their sculpture. An added bonus 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 foundries for 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 many artists consider a rubber mould of their original artwork to be a form of insurance. Founders also prefer permanent patterns – processing and casting is an altogether less nervous affair, waxes of a predictable wall thickness can be more easily produced from rubber moulds. Equally important, the founder can retain a permanent pattern as a quality control reference throughout the entire casting cycle, especially during the CHASING stages.
Clearly, permanent pattern casting allows the artist much more freedom to experiment with sculpting materials and techniques for foundry patternmaking. This next section looks at some of the more common methods and materials used in patternmaking for art foundries.
MATERIALS FOR PATTERNMAKING INTRO > |
