MIT FOUNDRY CASTS MEDALS OF SCHOOL SEAL

DMSE professor Krystyn Van Vliet came up with the idea of casting medallions for commencement when she was a graduate student in 2001. At first, grad students made all of them. Although I now lead and organize the process, it has evolved into a joint—and, I’d like to think, community-building—effort involving teaching staff and undergraduates as well.

During IAP, I start gathering students willing to donate their time and begin training them in the steps of what’s known as investment (or lost-wax) casting. First we produce and assemble wax copies of the MIT seal, made from a silicone rubber mold of an original medallion. Then we coat these assemblies with ceramic mold material, burn out the wax, and pour molten metal into the cavity left behind. Finally, the students finish the castings—cutting, grinding, polishing, and applying chemical patinas. The allure of molten metal is hard to resist, so the pouring is always the big draw.

We cast the medallions in silicon bronze (4 percent silicon, 1 percent manganese, and 95 percent copper by weight) and pour at about 1,100 °C. But while any metal pour is a spectacle, that’s the easy part. It’s the finishing work that really differentiates a great foundry from a good one. People new to metal casting are always surprised that there’s more work to be done after the metal has been poured than before. I estimate that each medallion requires more than one hour of work, all told.

To keep the free labor flowing, I try to make the medallion-making sessions fun—students come and go as they wish, we listen to the radio, and we try to keep things lighthearted. Sometimes I have more help than I know what to do with, and sometimes it’s just a student or two. That’s fine with me, because I am happy to be exposing students to the foundry and getting them some hands-on experience. Although each handmade medallion winds up having its own quirks and merits, teaching students the process is more important than the end product.

I believe all graduates of a materials science program should get to try metal casting. It is one of the foundational elements of our field and a critical technology in the history of human civilization. It makes so many fundamental principles of science and engineering clear, immediate, and tangible. And with materials science curricula and American industry evolving away from metallurgy, our medallion-making project might be many students’ only chance to see molten metal in person.

To read the complete article, see: A Labor of Love (www.technologyreview.com/article/526246/a-labor-of-love/)

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