Equipment that we used:

Old BBQ bowl (steel)
Brass Elbow (plumbing)
Copper pipe
Compression Hoint (plumbing)
EverBuild Fire Cement
Impact Drill
Adjustable Spanner
Center punch
Varying sized drill heads (to drill and expand the size of hole)
Air bed pump

Safety stuff:

Leather apron or any other suitable fire retardation equipment
Face protection
Bucket of sand (much better than water)

Step 1: Step 1: Finding Your Base

Because of the use of fire cement the initial base doesn't have to withstand the same temperatures that the forge will produce. However a steel base is preferable as heat will still be transferred to the base.for this try to use a steel base with a bowl like shape (the one we created is our first and smaller to allow us to understand how the materials work on a smaller scale). This base will be holding the coals through a layer of fire cement.

After this prepare the base by cleaning the surfaces the cement will come in contact with to ensure that the cement will fix to the surface.

Step 2: Step 2: Create the Airflow

For this fix the base in place and use a center punch in the center to help guide the drill bit, after this drill the base to create a hole smaller than the internal diameter of your Elbow piece. Next force the elbow to be threaded to bring more strength to the joint.

This will be reinforced later by the fire cement, also note that we have used a brass elbow and copper pipes, while the melting points of both of these metals are below the created temperatures they are safe from melting. This is due to both the fact that the temperature of the coals will be mainly directed upwards and that we will be reinforcing these pieces with more fire cement.

Step 3: Step 3: Connecting the Elbow to the Pipe

This pipe will supplying the coals with high pressured air which creates the high temperatures which can soften metals. In this case the elbow is connected to the copper pipe via a compression fitting. the pipe then leads to a safe distance where is connected to a air pump via an adapter for blowing up air beds (however we have found that the airbed pumps don't produce the temperatures that we are looking for and i would advise to look for a stronger system such as a leaf blower)

Step 4: Step 4: Applying the Fire Cement

The fire cement we used EverBuild which can withstand temperatures up to 1250C which means that the forge is not equipped to work with steel as the melting temperature is too strong for the cement.

The cement was applied to the base of the bowl and sides, the sides being 1 inch thick and the base 0.5 inches thick. Note that the cement will have a window of time in which it is malleable, EverBuild being 4 hours.

Step 5: Step 5: Firing the Forge

Now that the cement has finished setting, fill with coals and allow them for burn for some time before increasing the pressure of the air, after you have had the coals burn with the blower on let the coals cool down for 1-2 hours and inspect the cement, elbow and pipe for signs of stress from the temperatures. We found this setup to both provide us with enough to melt aluminium cans within 5 seconds while maintaining the structure of the forge.

Step 6: Finished

Looking back at this project we would have loved to choose a base with higher sides or a deeper bowl to focus the temperature more efficiently, as well as this we would also mount the forge on top of something so that we could use it without having to hunch down.

Another improvement in which we would introduce in any future forges would be a cap over the top of the airflow to stop coals from breaking down and falling into it, this could be as simple as small clay pot with drilled holes to disperse the air.

This is our first/prototype forge to test the mechanics before committing to a bigger operation.

Remember that that the best way to put out a fire at these temperatures is a bucket of sand, water may cause the molten metals to spit which is never fun so make sure you have sand available as well as a leather apron and face protections!

We also realise that this is our first attempt at this, and accept that both our forge and this instructable is far from perfect. We would love to here constructive criticism and take it on board =)

Thank you for reading and we hope everything works out within your project!