With the help of Uli Thie, a Technical Demonstrator at Massey, I took the hairdryer apart and rewired it to a 12v transformer, with the aim of having a constant air supply without the heat sensitive switch cutting the power.
I also constructed a new crucible from a piece of steel tube with a steel plate welded to the bottom. I don't have a picture here, but it is much sturdier than a steel can!
My idea this time was to pig the aluminium (a smelting and purification process to reduce slag and burn away excess hydrogen) and make a series of ingots for a second foam casting test.
I constructed a couple of tools for removing dross - one using a teaspoon, some steel wire and gaffer tape, the other is just a length of wire.
Above are some images of the scrap I have been collecting, including beer cans, tube and bar and swarfe from some turning exercises from the workshop at the university and the leakage form the last firing - with lots of charcoal embedded.
The firing was a success. It's taking about half an hour to get to a molten state, twice as long as stated on many websites. I think this is a combination of the new crucible and a lack of power in the fan. I am now getting a lot more used to the process, how much fuel to add and when to add it. I have a leaf blower that I could link up to the furnace, but think this is too powerful and would result in the charcoal burning way too quickly.
The dross tool is great for skimming big lumps of slag (as long as I am quite quick the gaffer tape doesn't melt!) and the rod is great for taking the fine skin from the molten material, which were dumped into the sand. As you can see, I cast the ingots in an old muffin tin, which works beautifully, and readies my for some further foam casting tests.
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