Random additional data points:
Courtesy of clueless renters, I’ve learned that stovetop elements are wrapped in ceramic. If you first heat it up to glowing red and then put a cold pot on it, it will eventually crack and fail. Inside you find a coiled heating wire. They were destroying half a dozen coils a year (!) before I figured this out. After cracking, they’re electrically conductive, so you may want secondary protection against shorting out against a metal container.
Thermocouples and PID controllers on ebay are stupidly cheap. No idea how rugged they actually are, I’m using it to heat my elderly cat’s bed sitting on top of an insulated wood box containing a (old, used) 40W incandescent bulb. That said, the SSRs are generally questionable, but for me, the bulb being on continuously isn’t a safety issue. OTOH, getting a thermocouple meter doesn’t seem terribly expensive either. If you want to build your own controller (i.e. computer / microcontroller driven wrt time/temp), adafruit has boards as low as $15.
Calibration is easiest done with ice and boiling water (as I do with kitchen tools) but I don’t know how well that extrapolates up to 1000C.
I hadn’t thought about unusual uses for excess power before, but you’ve given me some ideas (aside from running more servers for “free”)
Heating regular steel to glowing means you’re oxidizing the top layer of steel into rust. That black layer will flake off and means it’s getting thinner and thinner with every heat cycle. Ask any blacksmith! OTOH, if you’re in a low oxygen environment, it should reduce this effect. I had to point that out to folks who were building “rocket stoves” and didn’t understand why their steel burn chambers were eroding so fast. I don’t know how this applies to stainless, but stay away from galvanized! The galvanizing metals will outgas and can kill.
Good luck!