Steel yard identification via spark testing (1900s-1960s)

Historical PMI technique used in steel yards 50–70 years ago; demonstrated live on the grinder with chrome-moly, carbon steel, 440C, and 304 stainless samples.

Positive materials identification is a big deal. In that case they were blaming the welder. "He should have known when he was grinding it that it wasn't carbon steel." I said, how would he know when he was grinding it? Now, if he was working in a steel mill or in a shipyard in the 1930s or '40s or even '50s and '60s, he might have known. Or his father or grandfather might have known. Because there's something we used to use for PMI in a steel yard fifty, sixty, seventy years ago, called a spark test.

Tom's first-hand recollection from steel-company work forty years earlier; demonstration with grinder on 1018, 1045, 440C, and alloy steel samples. Used as the "ridiculous" (in the sense of low-tech, embodied-knowledge) extreme paired against LIGO.

That's what we do for big science. Now let's talk about the ridiculous. Does anybody know what I'm going to do with my grinder and my steel rods? We're going to do spark testing. Chemical analysis à la 1900s steel.