Earlier this week, I was one of 20 people on a tour sponsored by the Art Gallery of Ontario of the Artcast foundry in Georgetown, where Eric Knoespel (left) and his staff have been casting sculptures in clay and other impermanent materials into bronze and other metals for years.
We were walked through all stages of the process, from producing a rubber mold of the original (on the table in the picture at left), to making a wax duplicate which is then covered with a ceramic shell mold (which Eric is displaying, above and below).
(See the red wax inside the ceramic shell? Click on picture to see larger.)
The wax is then melted out of of the ceramic shell. The shell is fired for extra strength and then placed in a bucket of sand, at which time the molten metal is poured in the ceramic mold:
The mold and metal are left to cool, at which point the ceramic mold is chipped away, and voila! A bronze sculpture!
Okay, this is a very oversimplified explanation of how it's done — there are several additional steps throughout the process I've described, and afterward. For example, the Glenn Gould statue in front of the CBC Broadcasting Centre on Front Street was cast by Artcast, and a work that size has to be done in pieces, which means there are later steps in its reconstruction.
But essentially, that's how it's done. And Eric gave a great tour.