Cupola Furnace


    This is my latest interpretation of the cupola furnace for melting large quantities of copper alloy. It is based on descriptions from Theophilous and Birringuccio, along with some modern help from Stewart Marshalls book Building Small Cupola Furnaces.

    I set as a goal to push about 90 CFPM into the cupola from a single set of bellows based on suggestions in Stewarts book, using the bellows volume calculator in this site, however by the time the bellows were built the output was significantly less because they operated slower that I expected (need larger in/out holes). They did however produce enough to do the job (probably around 60 CFPM). The calculations in Stewarts book are really for melting iron with coke, so by the time you scale things down for copper with charcoal, it problaby worked out about right.

    Cupola - small bellows


    I added a set of small (11 CFPM) bellows on one side just to give a little extra air. I believe 2 sets of matched bellows, one on each side, would work best because the large bellows moved so much air that it melted the refractory on the small-bellows side. With 2 sets moving the same amount of air, it would hopefully center the blast better.

    The cupola parts are lined inside with a home brew refractory, and lined outside with a cement/colored grout mix. They are built from small freon tanks and sheet metal, with wire mesh outside to hold the outer layer. Since it was experimental I didn't spend too much time making them look nice.

    Cupola Running


    After the charge settled, I put a lid on it to retain some heat. The block of tin used to alloy the bronze is preheating on top. After all the copper melts, the tin is thrown in to make the alloy. If the tin were put in first, it would vaporize during the melt.



    As you can see, the large bellows are a bear to run with one person. I think the melting zone was only about 5" or so high above the tuyeres, where it should have been about 10", however it did melt 10 lbs of copper with about 30 minutes of bellows pumping.