Casting About, from Al to Zinc

by Jeff Sciortino The various stages of lost-wax casting Jeff Sciortino

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The great corn breeder John Laughnan used to say that the soil and climate of Champaign County, Illinois, were the best in the world for growing corn, but that they were not ideal. That is, given a chance, he could design a plot of land and a climate that would grow corn even better.


I feel the same way about elements. Iron is the best for building bridges, because it's very strong and very cheap, and it's easy to weld and machine. But it's not ideal: It rusts. The fact that iron is reactive and unstable in air is one of the great lousy breaks in chemistry. Given the chance, I would design a world in which aluminum was as cheap and easy to weld as iron.


When I was in my teens trying to find a metal for lost-wax casting, I felt this way about all the metals I tried. I wanted one that melted easily, was runny so it flowed into detailed molds, didn't oxidize when molten, and, most important, could be found cheap at Marco's Scrap Metal. This last requirement eliminated tin, the best casting metal for kids (hence tin soldiers).


Lead is a lot like tin and also comes as scrap (car batteries), but it's horribly toxic (which made me worry every time I used it). Aluminum was out because it didn't fill the finer details in the mold, although I now realize I should have used old pistons, not old storm windows, as my raw material: Pistons are made through casting and thus contain an alloy conducive to the process.


Finally I settled on zinc. I could just barely melt it (420