DIRECT PLASTER MODELLING
Plaster of Paris is a highly versatile sculpting material that is ideal for multiple tasks in the studio and foundry alike. When correctly prepared and applied, plaster is capable of creating exceptionally strong and lightweight master patterns with a lengthy storage life. The raw material itself is inexpensive and requires little in the way of equipment for use. In sculpture making, plaster of Paris can be used either to create waste moulded casts, or else be applied directly as a construction material with it's own unique working qualitites.
WHICH TYPE OF PLASTER?
There are numerous versions of the basic plaster product available, most of which are formulated for the construction industry. An sculptor might have some special reason for using a dedicated building product such as a wall plaster, but for normal studio and foundry purposes wall and other construction trade plasters are not considered ideal.
The group of plaster products that are of most interest to the sculptor are based on the 'fine casting' and 'dental casting' versions. The product names and fomulations may vary according to manufacturer, but a choice of one from this group of plasters should be adequate for most studio studio based tasks.
One of the most effective methods of creating a large scale foundry pattern is to work SCRIMMED plaster over an expanded polystyrene cut foam core (JUTE SCRIM is a coarse woven fabric). A well made foam/plaster/scrim construction should result in an easy to handle foundry master pattern which is strong enough for either lost wax casting or sand moulding (see SAND CASTING). A foam core can be roughed out into a volumetric form by hot wire cutting, then fine tuned with a cheese grater. The foam core is finished by skinning with scrim and plaster. If necessary, the foam core can be stiffened and reinforced by inserting steel bars into the polystyrene.
An assistant with Andrew Burton's
'Rudder' (Tyne & Wear Dev.Corp.)
Plaster constructed over a foam core.
(© A. Burton)
Founder's calculation worksheet
for the 'Rudder' element showing
pattern cut lines
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