Just did a quick experimental etch with citric acid; pretty mild stuff, but the FeCl3 is on order now (in pellet form; didn't fancy the prospect of having to hump a 5-litre drum of liquid acid about). The result's been mixed. It's definitely resulted in a slight etch; problem is that, just as with the de-corroder, it's also dulled the surface. I'm not sure whether that's something that's inherent to the etching process, or if I'm just making a mess of it.
Hopefully, even a dulled surface can gently be polished back to life. Anyway, I'm going to proceed with a test etch using FeCl3 once I've got it and made it up to the appropriate strength. Should be good; fingers crossed!
