The part wrapped in aluminium foil is also lightweight
concrete blocks. The inner walls are thin sheet steel,
I think 0,7 mm. This furnace heats up pretty quick.
The blocks are supposed to last longer if you keep
them dry, I guess especially during the winter. If you're
melting aluminium, make sure pieces that go in are
absolutely dry and preferrably preheated, hence the
small electric oven on the side. Introducing moisture
to molten aluminium is not a good idea
as this may cause explosions.
