From A to Z
Making an Ocean SunfishThe Giant Ocean Sunfish was a commission for the National Museum of Scotland to produce a life-size model (11 feet high) to be displayed in their new Natural World Galleries.
The model would need to be strong but light as it was to be suspended above the public and so could be viewed from various levels on their mezzanine floors. So for the first stage I decided to give a simple visualisation of the scale in relation to a human for the client so I sculpted a scale maquette in clay which was made 1 inch to 1 foot.This small model was then photographed and placed in scale with a figure in photoshop. However a maquette has the main purpose that it can be used to get general approval of the sculpture by the clients and any adjustments can be made simply and quickly.When the maquette had approval I then made a silicone rubber mould of it which, after the original model was removed, was then filled with a polyurethane liquid material. After setting hard I had a solid cast of the model which could be handled without damage.
Scaling upOnly half of the maquette was actually cast so that it could be fixed flat onto a board and vertical cuts sawn at even spacing like sliced bread. By placing card into these slots and then tracing the outlines meant that a series of contour lines of the overall shape were obtained. These outlines were then scaled up 12 X to full size. I then traced these large outlines onto sheets of polystyrene which were cut out and placed together in sequence and attached to a centreboard made of plywood. This result was then mirrored so that polystyrene could be added to both sides.The centre board is supported by a strong metal frame which is able to take the weight of the clay and the mould.
This polystyrene shape was made several inches undersize so that it formed the under shape for the sculpting stage.The polystyrene was then covered in plaster re-inforced with hessian cloth. Once set the hard plaster outer shell was sealed with shellac which could then receive the sculptors clay.
Moulding and castingOnce the sculpting was finished a mould was made in silicone rubber. This material is brushed on in several layers to build to the required thickness. Fibreglass is added to this surface to give the mould it’s supporting jacket. In the case of the Sunfish all the fins were made removable so that they could be moulded and cast separately. The mould of the body was only in three pieces, often more complex sculptures require numerous sections to be made, but the mould was very large and so quite labour intensive.
After the mould is taken apart and the original clay sculpture removed then polyester resin which can be tinted with pigments is brushed into the mould, capturing all the fine detail which when hardened is backed up with a few layers of fibreglass cloth which is saturated with more resin. The separate pieces of the mould are then bolted together with another fibreglass mix which joins the parts together. When cured the mould is unbolted and the cast is revealed. This hollow fibreglass shell is both strong and light.