Bronze Casting Process

Our current Programme Assistant Vivian Ross-Smith has been busy during her last few weeks here with us, by trying her hand at some bronze casting for the very first time. Vivian’s work is heavily influenced by process, she considers her relationship with the remote islands she knows well, by exploring traditional craft in contemporary ways. Find out more on her practice by visiting her website.

With the support of our two technicians Eden and Uist, Vivian was able to access the foundry and try out some bronze casting. It was a busy time in the workshops with a students group from Clermont-Ferrand School of Fine Arts also working with bronze. As part of her practice, Vivian makes intricate fishing nets, so chose to knot together two small nets from rope to use as a form for her casts. The most appropriate method of mould-making for this complex shape was to form a ceramic shell mould.

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Once the net was complete, a nice hot wax dip was used to seal the rope and start the wax process. Rods of wax were formed and cut down to size before being melted together forming a network of ‘runners’. To ensure an even distribution of bronze gets around the whole mould a runner was fed into the back of each knot of the net – a pretty fiddly process! All the runners linked up to a ‘cup’ where the bronze will be poured into.

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After lots of wax work it was time to start the dipping process, building up many thin layers of dip and powder coating, encasing the wax structure in a hard ceramic shell. The dipping process is quite time consuming as each layer needs to be left to dry in-between coats. When wet the dip is a fluorescent yellow but once dried turns to a warm orange colour – a handy visual reference for knowing when the piece is ready for its next coat!

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The moulds with their finished ceramic shell

The moulds with their finished ceramic shell

On the morning of the pour the wax and net from inside the thick ceramic shell has to be burnt out to be left with a hollow mould to pour the bronze into. This is done by putting the moulds inside the barrel kiln and blasting the pieces with fire to melt out the inside’s.

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With the ceramic shells hollow they were kept warm in the outdoor kiln to ensure no cracking when the bronze is poured in.

For a bronze pour at SSW an underground furnace is used….it takes just over an hour to heat up, with small chunks of bronze being added gradually to the pot. The metal gets heated to a phenomenal 700 degree’s centigrade and proves to be completely captivating for all spectators. An exciting time in the process! When the bronze was at optimum temperature the moulds were laid out and sand shovelled around them to keep them steady during the pour.

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When the pouring is complete the moulds are left plenty of time to cool before the cleaning and finishing of the casts can begin. All the carefully built up ceramic shell can be knocked off to reveal the cast beneath – a really exciting time, like unwrapping Christmas presents!

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The casts were neatened up by removing all the runner and using a dermal to shape the backs to replicate the rope texture. A good thorough sand blast removed the last of the stubborn ceramic shell, which was clinging on to all of the casts nooks and crannies! Followed by a good buff with a wire brush to give the piece’s a nice surface shine.

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The casts were a great success and Vivian was delighted with the results! There are lots of options for using patina or wax coating here at SSW, but Vivian has opted to take the nets back to her home of Shetland to immerse them in the sea in order to gain a natural patina and colouration on the casts.

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If you fancy having a go at bronze casting yourself why not join us for an upcoming bronze casting course? Our next course is in October, it’s filling up fast though with just one place left. Email arts@ssw.org.uk to reserve that last place, but don’t worry we usually hold a couple a year so there’s plenty of chances to get involved. Further information here – http://ssw.org.uk/?p=4516

At SSW we also hold an annual welding course, which we are also currently taking bookings for, follow this link for further information – http://ssw.org.uk/?p=4519

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