Next I took that clay and made a 3-part mold using plaster. Before coating in plaster I covered the skull in vaseline to make sure the clay would part from the plaster (which ended up not working and later being ripped out of the plaster ruining the clay version :( )
Here is the 3 part mold:
After creating the mold I poured in some melted wax and sloshed it around the inside of the mold, and then poured out the extra wax. I would wait for it to cool and then pour some more wax, slosh, empty, repeat. I did this several times. I did this to create a hollow version of the skull so to not waste extra metal when casting.
The resulting wax version of the head was this:
I then took this wax version of the skull and covered it in several layers of slurry (a mixture of sand and a cement like mixture). Sadly I forgot to take a picture of this stage.
After creating the slurry mixture it was then time to pour the molten metal into the mold. After pouring and cooling I broke the mold to reveal the aluminium skull.
Here it is after breaking the mold:
The mass at the bottom is the spout where I poured the metal in. Using a saw and blow torch I removed that part and cleaned up the skull.
Here is the final aluminium skull after clean up: