FeCl3 is that stuff we use to etch circuit boards; apparently there are other uses for it too. It etches most things, including, it would seem, the lid of the jar I kept spent etchant in, the M10 studding on the bench underneath, and most surprisingly for me—for my chemistry is rather rusty—the plastic cap of the clamp on the shelf in front of it.

Here’s the damage control:

The studding was a mass of rust in the middle. I hated to throw it, so I took most off with a wire brush and then, lacking a die, re-cut the thread with a nut, a spanner, and washing up liquid for a lubricant. Now that is why we store it carefully in a large jar with plenty of space…