That's a lump of yellow brass, with a bit of copper wire dissolved in it. Things had to be beyond yellow hot to make it melt, and I had difficulty maintaining the heat around the little steel crucible - the charcoal needed nearly continuous tamping. I've figured out that dry bits of 20x20x80mm dry wood seem to be about right to maintain a stream of nice charcoal at the bottom of the furnace. The sweet spot isn't very big, so a crucible half the height of my current one is realistic.I'll have to work on channelling the air to a more precise point, and getting the fuel funnelling into a smaller hot zone. I'm going to need a lot of fuel when I try melting iron, just for weight to ensure the air blast doesn't blow it all out the chimney!
Experiments have revealed the amazing coincidence that a beer can is about the right size for the furnace core of a mini-cupola that I might be able to power with a cheap leaf-blower. Well, I've managed to melt the end of the hot air stripper anyway...
