My first furnace

Click on any image to see a full size picture.

First flare the gas from your chosen propane tank. Getting an empty one in the first place helps greatly.

Once its empty, unscrew the valve from the top & steam it out.

I did this by putting a pint of water into the tank & I heated the underside with my burner to boil the water off.

This removes any residual propane. It doesn't smell too nice though.

Now cut the top off with an angle grinder or hacksaw.

Cut a hole in the side for a burner & one in the top for an exhaust.

Burn a hole in the bottom.
This is to allow an escape route for molten aluminium if the crucible fails.

I welded up the crucible from scrap hydraulic pipe at my college welding course.

Now find something that when inserted into the tank will give you a clearance of 2 to 3 inches.

The coffee cans I chose were not broad enough so I wrapped cardboard around them to reach my desired diameter.

The finished 'form'.
I didn't trim off the excess cardboard as I wanted something to get a grip of later to pull the form out.