One of the skills I wanted to learn this year was how to make bronze and then cast with it. As with my interest in flint knapping, I wanted to see how prehistoric man made tools from scratch using metal they formed themselves. Part of my interest in this was ignited by the idea of casting into sand- one of the materials I gather at the tidal foreshore, and went to the Goodwins specifically to collect-but also I was fascinated to see that unlike most bronze casting courses, Will Lord offered a course where participants made their own bronze as well as learning how to cast with it. To me this was a compelling reason to work with him.
I absolutely LOVED doing the bronze casting -every element of it was fascinating and exciting to witness, a constant alchemy. It was also extremely physical, which appealed to me. I did the course with two other participants, John and Lesley over two days at Will’s studio near Bury St Edmonds. Day one was focussed on making a furnace and smelting copper (a component of bronze), and looking at lost wax casting techniques. We started by building a smelting furnace in Will’s garden, using natural materials: clay (in the form of bricks made from locally dug clay), grog (gritty clay), horse manure and deer hair. We had to mix the four up- crumbling the manure and hair, crushing the grog and then mixing the component materials together, in the ratio of two parts of grog, to one of clay, one of manure, and one of hair. We then used these mashed up materials to make “bricks”, which we then stacked on a paving slab to make a kiln shape, that was a bit like an igloo, with a hole/vent for bellows. All this was done outside in the garden. Meanwhile we took it in turns to crush a large lump of malachite placed between a leather hide, which we hammered with a stone to reduce it to small pieces. Historically in Britain this malachite would have come from somewhere like the Great Orme mine in Wales.
We lit the furnace by using flint and marcasite (iron ore, which had come from the Warren in Folkestone) to strike a light onto a bit of amadou (silver birch canker, I think). Once we had flames we blew these onto a nest of hay with bulrush fur. It soon caught and we placed it in our furnace, feeding turps rich pine (punk wood) and then charcoal on top. Then a pair of Will’s bellows, made from hide, came into their own. We took it in turns to squeeze these to bring the furnace up to temperature, and then to keep the flames and heat going. The furnace was ultimately capable of reaching temperatures of 1300 degrees. It was really physically hard work manning the bellows, to constantly keep the fire going, and made me realise how vital it would be to have help if I tried this at home.
We put the crushed malachite in a graphite urn and placed it in the furnace. Once the malachite melted we emptied the crucible into the charcoal so it that it could percolate down and transform into a copper ingot.
We spent the rest of the afternoon making models from wax to use to cast the following day – the lost wax casting technique.
Will had different types of wax and showed us how to manipulate them into a shape with a pouring cup. I made a version of a deer bone I had found mud larking on the Thames. Because I wasn’t happy with it, and I was quite fast at modelling-probably because I was in my comfort zone with it- I made two more models. We were supposed to make one, but Will suggested I try them all. We covered our models in a glaze of slip and built a thin wall of more of the clay mix from the furnace build over them. Once Will was happy that our wax models were well invested, we left them for Will to take home to dry out (apparently by leaving them in the oven at 50 degrees all night, with the door open), so that they were ready for burning out and firing on day 2.
Our day ended with a demonstration of how to pour bronze into a sand mould, using bronze Will had already made which he heated in the smelting furnace. He showed us how to pack a wooden double sectioned mould with modern casting sand and make a blade shape from a pre made wooden form. Seeing this process was really inspiring, and it was amazing to think how our days work translated into the beautiful emergent axe form he created at the end of the day.
Day 2 was about burn out and casting. First of all we had to burn the wax out of the lost wax models we had made the day before, and raise the temperature of the mould. Whilst that was happening we weighed out tin to mix with the copper we had made. This was done in a crucible in a modern gas furnace system. Whilst it could have been done in the smelting furnace, Will needed us to have molten metal at the exact time we needed it with our lost wax pieces, and with three participants this would have been more uncontrollable in the prehistoric method.
When Will could see that our wax had melted we took it in turns to pour the bronze we had made from its crucible into the moulds, which we stood in a bucket of sand. This was where we understood how key the pouring cup was. Once our mould, now full of bronze, had cooled a little, we cracked open the moulds with a pick axe. Mine had corrupted quite a lot from the original bone shapes I had made, and I abandoned one as having too many irregularities to spend time trying to clean up, but the other two I filed down and sanded (Will has a brilliantly equipped workshop).
In between doing this I sand cast a wooden form akin to a knife blade and a flint arrow head that Will had knapped. We prepared boxes as Will had demonstrated the day before: packing them tightly with sand and laying in our objects by the pouring vent in the box and making a vent in the sand between this and the object. The box was then clamped shut and we poured molten bronze in as before.
My two sand cast pieces both came out really well too: personally, I found the knife form too flat and prefer the subtle planes of the flint that have been picked up by the bronze. I am really delighted with the all my outcomes but to be honest it was more about the process for me than the result. Every element of the bronze casting was exhilarating for me. I am really desperate to try and repeat this process. I think I have found somewhere where I can do this safely so my intention is to recruit some helpers and try it myself soon! As an introduction to bronze casting, I really recommend Will’s course-it is very satisfying to think you have made both the metal and the mould that you cast from: and by building the furnace you really get a deeper understanding of the process.
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