Lost Wax Investment Casting

Lost-wax investment casting is a millenia old metal-forming process. Jewelry (like brass rat MIT class rings!), superalloy turbine blades, and dental fillings are just a few things created by investment casting.

To cast, you do the following:
- make a wax or plastic model of what you eventually want in metal
- create an investment mold (from a sandy, plaster-like substance) around the wax model
- heat up the mold to melt/burn/vaporize the organic model out of the ceramic mold and to harden the mold
- pour molten metal into the resulting cavity (an inverse of the wax model)

The shell mold is then broken and a metal replica of the wax pattern is found. Casting picks up the details found in the model, every tiny one of them. Your casting will look just like your model, except maybe 5-10% smaller (due to shrinkage upon freezing).

During MIT's Independent Activities Period '99 and '00, Benjamin Linder and I taught a short course on lost-wax investment casting. I was a graduate student in metallurgy and Ben had just received his doctorate in mechanical engineering. (The two of us started doing this when Ben decided he wanted to make his own wedding bands.) We've taught about 30 people how to cast. They cast in aluminum and bronze, although gold and silver also were possibilities (if they had wanted to pay for it, of course).

It's all one big game of making models and inverses of models in which to pour something molten.

Here is an example of a casting that I've made.
(It's a sculpture of Don Quixote ... it was a gift to a friend's father, who collects Don Quixote figurines.)

Here is a link to the American Foundry Association whose Foundry Education Foundation Conference I attended twice, and here is a link to a very informative article in the Journal of Materials about ancient lost-wax casting in India.