There’s something awe-inspiring about knowing that the lost-wax casting process I use to make my sculptures has not changed in over 6,000 years. Also known as precision casting, investment casting or cire perdue, lost-wax casting is an ancient technique that replicates an original sculpture in metal. Bronze is my preferred material, although it can also be achieved with any alloy including gold or silver.
Early examples of cast objects have been found all over the world, in the Middle East, Asia, Egypt and the Mediterranean, Northern Europe, South America and West Africa. The earliest was found in Pakistan – an amulet cast into copper and at least 6,000 years old.
LOST-WAX CASTING PROCESS
The lost-wax casting process, which involves a series of stages, hasn’t changed over the intervening millenia. A mould is made of the original model. This comprises a rigid outer mould containing a soft inner mould which is an exact negative of the original sculpture. Molten wax is then poured into the mould and swished around so it forms a thin skin. This hollow wax positive is then covered in a liquid ceramic coating and baked upside down in a kiln. The coating hardens to form a ‘ceramic’ shell and the wax melts out. The negative space that was filled with wax can now be filled with molten bronze or another metal. When that has cooled, the shell is hammered off and you are left with a perfect replica of the original model.
Sounds fairly simple, doesn’t it? Of course, it isn’t. It is a highly skilled and complicated process. I am very lucky to work with Lockbund Foundry who have been casting my sculptures for over 25 years. Their considerable expertise has enabled me to really challenge the limits of what is possible with bronze casting. Simon Allison established Lockbund in 1993. He has always said to me, “Sculpt whatever inspires you. We’ll work out a way to cast it.”
WORKING WITH LOCKBUND FOUNDRY
The symbiotic relationship I enjoy with Lockbund is absolutely key to my work as a sculptor. We have a mutual respect and understanding. I will always be grateful for the support and encouragement Simon showed me at the start of my career. He took a gamble when he sponsored my first sculptures, but we have grown and developed together.
When I got my first big commission for the Goodman’s Horses, the foundry had to be rebuilt to handle the scale of the project. It was so much bigger than anything we had tackled together before. The new crucible was capable of producing 40-350 kg of molten bronze in one pour. Recently, Lockbund invested in a new induction tilt furnace to cast my Ammonite Cretaceous and Ammonite Jurassic in stainless steel.
Lockbund taught me to make moulds when I was just starting out, so I know each stage of the casting process first hand. The process of lost-wax casting might be ancient, but modern materials like silicone, fibreglass resin and jesmonite have streamlined it and made it more efficient. So too has progressive technology, enabling us to produce more innovative forms. For instance, my sculptures of boxing hares really tested the structural limits of bronze casting. I was able to arrange dynamic poses which utilised the strength of bronze. Bronze’s tensile strength allows compositions with minimal supports, unthinkable in materials such as marble, wax and plaster from which sculptures are initially created.
So even though sometimes my sculptures require complicated moulds, Lockbund Foundry always rises to the technical challenge. They have the technical expertise to cast even the most complex of my wildlife sculptures into bronze, preserving all of the detail of the original. It is one thing for me to push my finger into wet clay, but Lockbund can reproduce even my tiniest gestural detail in cold hard metal. Their ability to do this always amazes me. I love the fact that a finger print left in the clay original comes through into the bronze.
Once a sculpture has come out of the foundry, I apply the patina. Most sculptors leave the decision about patinas to the ‘patineur’ in the foundry, but I always undertake this part of the process myself. I’ve studied the different uses of chemicals and how to apply them to achieve the various effects I am after. I rarely, if ever, opt for a traditional finish. I generally prefer a dusty finish which suits my wildlife subjects, rather than a slick and shiny look. For me, it is like the final layer of paint on the canvas and as much a part of the creative process as the initial modelling.