< LOST PATTERNS
MATERIALS FOR CREATING LOST PATTERNS
When creating a LOST PATTERN wax casting, the artist's original model is incorporated into the investment mould, then burnt off to leave an air gap which can be filled with metal. This means that the artist must model their design in materials that can easily be evacuated from the investment mould during a kiln burnout.
Traditionally, artists working with the lost pattern technique have used wax as a modelling material of choice. As well as satisfying all the technical demands of the casting process, wax is also an excellent modelling material in it’s own right. Wax can easily be blended to create a variable working medium; BLENDS can be formulated to make either a very hard, or very pliable modelling medium - as well as a balance anywhere between these two extremes. Wax can also be COLOURED to suit personal preferences. Few wax blends deteriorate or dry out in the manner of clay and related modelling materials, so with care, good quality wax sculptures can be kept in excellent condition for many decades. Hardly surprising then, that many artists use wax a working material, even for sculptures not destined for art foundry casting.
Materials other than wax are also suitable for use in lost pattern casting, especially when a CERAMIC SHELL investment is being used to create a refractory mould. The thin, but thermally efficient ceramic shell enables kiln heat to penetrate more easily into the mould and purge enclosed pattern materials. In addition to wax, suitable lost pattern materials can include tallow and other fats, vegetable and organic matter including balsa wood, paper, card, straw, expanded polystyrene foams and fabrics to name but a few possibilities. Even certain plastics and low melting point metals and alloys (lead, tin, bismuth, pewter etc) can be use for making lost patterns.
LOST PATTERNS – A SUMMARY
Lost pattern casting is a relatively quick, easy and cost effective method of producing small scale casts of models formed in low melting point materials. The founder does not have to produce a rubber reproduction mould or a wax copy for casting, so costs can be significantly lower than those for a similar cast with a rubber reproduction mould.
The artist is restricted in the materials they can use to make a lost pattern – they must be easily combustible and there are also usually practical limits to the scale of work that can be made. If any part of the founding process goes wrong, the artist may be faced with having to re-create the design from scratch. Not every founder is willing to take on lost pattern work, and those that do may not refund payment in the event of a miscast. The founder may also surcharge the artist if the cast is excessively heavy, or if the cast requires a good deal of extra finishing due to faults arising from a poorly prepared wax.
Most lost pattern casts are intended as ‘one off’ or unique casts, though an edition can be produced by 'lifting' a rubber mould off the completed metal cast at some future point.
PERMANENT PATTERNS >
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