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CREATING A MOULD
OPUS STUDIO
There are a great many different ways of creating moulds and the technique chosen when working with a given master will depend on the material, it’s shape and size, and the number of copies required. The photographs here show the basic steps in creating just two common types of mould.
Creating a Mould
Silicone rubber ‘butter-on’ mould supported in a GRP case. This type of mould is commonly used for the larger subjects, and where the original sculpture is of a generally regular shape.  It has the advantage that very large monumental forms can be achieved, enabling the creation of striking exterior public art work, often built from many moulds and subsequently assembled from sections.
Shim is fitted around the circumference of the original.  This enables the two parts of the mould to be separated later. The fist layer of silicone is carefully applied ensuring that no air is trapped. The shim is joined to create a continuous strip and fixed using silicone. First layer complete. Additional studs are added to provide correct location between the silicone and the GRP case. Stiffer layers of silicone rubber are then added to build up thickness. The thickened rubber is then made smooth and the studs are removed to be replaced by fibre-glass. Chopped strand fibre-glass mat is then cut to the size required. This side of the mould is then completed by constructing a full GRP case. After allowing the fibre-glass case to harden, the sculpture is then inverted so that the process can be repeated on the other side. Holes are drilled in between each locating stud to accomodate the bolts which will be used to re-assemble the mould. The excess fibre-glass is then trimmed and 'de-nibbed'. This shows the finished mould being disassembled. The plastic shim is removed. The last piece of silicone is then carefully cut and the two halves of the mould can be taken apart. A layer of white gel resin is applied to form a hard smooth surface insidethe GRP case.
Silicone rubber block mould Generally, a simple block mould would be used for fairly small items, where it is economical to encase the entire original in a solid block of silicone rubber.  Using various adaptations of this process it is possible to create extremely accurate and highly detailed copies of an artists work.
Removing the clay original. The original is mounted and fixed onto a board to support it. A cardboard frame is assembled and liquid rubber is poured into it. After curing, the rubber is carefully split down the side. The mould is sliced with a craft knife and eased apart. The artists original is created, in this case using unfired clay. The interior surfaces of the mould are cleaned to remove any clay residue. The mould is assembled and taped securely. After curing, the first cast is revealed. The raw casting, prepared for finishing. The finished reproduction. After polishing and waxing the lustre of the bronze is brought out.
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