Tuesday, 1 February 2011

Hot 'n' Heavy, Wet 'n' Wild

I spent all but a couple of months of my three years in Sculpture at Art School, learning nothing but techniques, ignoring 'art' almost completely. Cro will vouch for that - we both attended the same art school at the same time.

I did a little stone-carving, but what eventually attracted me more than anything else was bronze-casting. Being the first (in a small group of about 8) students to inhabit the newly fitted-out sculpture department, we had the best of everything, thanks to funding due to the fact that Anthony Caro had attended the same sculpture department before he became so inexplicably popular.

We had a state-of-the-art foundry in the department, and the gas-fired furnace attracted the envy of the local Morris Singer art foundry, who used to cast for all the big names in the art world, including Sir Henry Moore.

Bronze casting is an extremely dangerous activity for many reasons, but the prime reason is the simple fact that molten bronze and water do not mix. We were shown safety videos by Morris Singer, who had conducted a few experiments by mixing potfuls of molten bronze with water, with spectacular and catastrophic results. In the slow-motion film (taken from behind bullet-proof glass), the bronze sinks to the bottom of the water, then rises back up again. When it reaches the surface once more, a chemical reaction takes place with the hydrogen molecules in the water, and the bronze explodes with the force - weight for weight - of the same amount of modern high-explosive. That is A LOT of high explosive. When you remember that the bronze is already red hot and molten, then this means that the 'shrapnel' from the blast causes secondary injuries when it sticks to your skin and clothes, slowly burning it's way down to the bone. A small drop of water from the ceiling of the foundry - landing into an open pot of bronze - can have similar consequences.

For these (and other) reasons, the process of a 'pour' in bronze casting is carried out with a ritualism so strict, that it would make a Catholic High Mass seem slapdash. The ritual goes as follows:

The metal has been put into the huge crucible (which is thrown away after x amount of pours, just in case it breaks while you are carrying it half way through) and the furnace switched on with a deafening roaring sound (over which you have to shout, and which lasts for a couple of hours); the empty (and pre-warmed) mold has been buried in a DRIED sand pit at floor-level; silica sand is sprinkled liberally over the concrete floor to guard against splashes; bricks are strategically placed to put the crucible on before the pour; iron implements are pre-heated over the furnace-mouth, to avoid the shock of cold metal against hot; the four people who are going to conduct the pour go over their coordinated movements one last time in a final rehearsal; they then don leather jackets, leather aprons, leather boots with no laces to catch molten metal, leather gloves, leather hats, cloth masks and full-faced visors which immediately steam up with their sweat, making it extremely difficult to see where they are going and what they are doing.

The furnace is switched off, and the room is eerily silent, with only the clicking and tinkling of shifting metal, fire-brick and sand under footfall. The dross raker picks up his hot rake and assumes his position. One pourer slides the lid of the furnace to one side, and a blast of heat comes from the pale pink metal and crucible inside, where everything has assumed the same coloration. DRIED oak chips or de-gassing tablets are chucked into the pot and given a stir. The two pourers get either end of a massive set of steel scissor-tongs and reach down into the furnace, grabbing hold of the crucible and praying that it does not burst on the way up. The full crucible is about 25 inches high and weighs about 280 pounds (a lot bigger than the one shown above). The tongs weigh an extra 50 pounds on top.

The pourers slowly take the crucible to the steel 'shank' and place it into the central ring, being careful not to knock it - the carborundum pot is soft and sticky by this time, feeling as if it will burst any minute. They then walk away with the tongs, then return to the shank and pot, lifting it over a pile of dried sand and tilt it slightly so that the metal reaches the rim. Then the raker gently rakes off the dross skin from the molten metal and steps a few paces back when he has finished. The pourers slowly walk to the mold, and begin to pour the metal into it's funnel mouth. When the red-hot metal appears in the little 'riser' holes at the top, they know it is full so they stop pouring. They then slowly walk back to the bricks and place the pot down on them in a reverse process, taking the tongs and putting the crucible back into the furnace. They then gently close the lid... and run like fuck in case the mould explodes! This whole process takes about 2 minutes, but at the end of it, everyone is utterly exhausted and overheated.

I was doing a pour at college for one of the teachers once, and it was a big mold, but I didn't know how big, because I had not seen the wax positive being 'invested' in it, so I had to go on what the teacher told me. Everything was going fine, and I began to pour the metal into the mould, waiting for it to appear at the risers. And I poured... and poured... then I started to tremble with fatigue at the weight of the metal and the position I was holding to pour it. I shouted through my mask - "Surely it must be full by now - how big is the bloody thing?" Then, from behind us, we heard the first of a number of explosions as a stream of molten bronze snaked it's way across the floor, bursting the concrete as it went. We were encircled by the molten bronze which had escaped from the split mold and found it's way through the sand and over the floor.

We were well disciplined however, and all our emergency practice came into reality. We slowly returned to the furnace as the floor exploded around us, sending showers of molten metal and hot concrete over our heads. We picked up the crucible as the raker opened the lid of the furnace, then we gently replaced it inside as the raker gently but quickly closed the lid whilst trying to avoid the shower of red hot rain around us.

Then we ran like fuck!


  1. I acted as a 'pourer' for you once. Never again. Too bloody dangerous; too bloody HOT.

    The end result was a cast bronze baby's torso, which I believe someone stole!!

  2. That's funny, I don't remember that, Cro, though I vaguely remember the torso.

  3. P.S. - They're making a right mess of that pour above - bronze all over the place.

  4. I never knew how much work and trouble went into something like that. I can imagine all the rules they must now have in art schools.

    I would love to know how they make the molds.

  5. That's it, no more bronze objects for me; I don't want to inflict that on anyone. I'm going to stick with purchasing marzipan figurines.

  6. Maybe it was for Mitchell or Franklyn even.. Can't remember. But I was 'Shanghaied', as being a 'big strong boy'.

  7. I found this very interesting Tom. When I was young I worked for a year or two in the offices at Ruston and Hornsby in Lincoln - in the foundry offices. Outside my window they were casting huge engine housings HRR 45 was the largest they cast and it took days to set up and when they poured the molten metal in they did it from walkways over the top. Looking back it was a bit like hell. Thanks for the reminder.