I am often asked "How did you do that?" when it comes to bronze casting. It always makes it easier to explain if I happen to have some pictures handy. In the case of my sculpture "Chutes n' Balls", the original piece was made out of Victory Brown microcrystalline wax. I used red wax to create the gating system and pour cup that would eventually serve to allow the hot bronze to flow in through the mold that I would make of the piece and provide a channel for the air and gases to escape. The gated piece was attached to a base board and surrounded by a flask (sleeve) made of chicken wire covered with tarpaper to make a container for the mold. Investment (mold) material made up of sand, plaster and silica in a 2:2:1 ratio, was mixed with water and poured into the flask.
After the the invested mold hardened, it was fired in a kiln for approximately 30 hours to burn out all of the wax, leaving empty spaces where the piece and the gating once were, and drying the mold. The mold was then placed inside a wooden frame
and damp sand was packed tightly in around it to keep the heat in and to help hold the mold together during the pour. The hot bronze was poured into the piece through the pour cup at the top of the mold, filling all of the empty spaces in the mold. The next day the mold was broken open and the cast bronze, including the piece, the gating and the pour cup, were removed. The next step was to cut off all of the gating and the cup and then to chase the surface with files, chisels and Dremel tools to remove any imperfections. Finally the piece was cleaned with a brass wire brush drill attachment and sealed with Butcher's wax.
It's a lot of work, but so worth it in the end.
*Additional images of 'Chutes n' Balls' can be found in the Sculpture
& Slideshow sections of this website.