Casting About, from Al to Zinc

The best metal for the job isn't always the ideal one.

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

by Jeff Sciortino

2. Plaster of Paris is poured around the wax model to form the mold.

by Jeff Sciortino

1. Melted beeswax is poured into a plastic mold, fashioned from casting resin, to create a mini periodic table.

by Jeff Sciortino

6. The various stages of lost-wax casting.

by Jeff Sciortino

5. After the zinc has cooled, the mold is broken to reveal the metal casting.

by Jeff Sciortino

4. The molten zinc is poured into the now vacant mold.

by Jeff Sciortino

3. While the wax is baked out in a toaster oven, zinc is melted on an electric burner.