Stone to Bowl. Copper smelting

Finally I am three weeks into my Stone to Bowl residency and I feel that I should share progress.

One element of Stone to Bowl is to develop a replicable way of smelting copper from malachite/copper ore in a traditional way that means that I can work in the landscape anywhere.

First task was to source some Scottish copper ore. The mine in Bridge of Allan is long closed, but I found some copper traces on the waste heap. These photos show the mine entrance and the pieces that I collected.

After initial smelting experiments I have been putting the ore in closed ceramic  balls with added charcoal to give a reducing atmosphere for the smelt. (While I was on my residency another artist was successfully smelting malachite using oxy-acetylene.)

The furnace is charcoal burning; and for these experiments I was using an electric air blower, although I will use bellows when I understand the process more. The dry ceramic balls are made of a local refractory clay mixed with fibre -horse dung, and sand. Inside is copper ore in pea size chunks  with 25% charcoal. The balls are placed on the furnace charcoal once it is burning well and the furnace is run until the ore is to a high enough temperature to smelt, hopefully. The balls are then plunged into water and broken open.

The first smelt was not a complete success. Some copper was formed, but a lot of this was pelletised rather than consolidated and some had to be panned from the ashes of the furnace.

cupan

However I reheated this copper to consolidate it and a reasonable amount of copper was retrieved. Again I used an electric furnace for this process while I am experimenting.

IMG_1370

I am not sure that a chimney furnace is needed, a horseshoe hearth might be as successful as one can see what is going on. The chimney furnace is made of a refractory clay mix similar to that used for the balls.

I tried another smelt later in the residency of which more anon.

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