Well, went and got some cerium oxide (FREE from my local glazier) and a big bag of iron oxide too ($2.25 from a pottery shop). Should keep me out of - or into - mischief should the UHTC and vinegar fail
Spoke to the glazier, and he said if it is water condensation, they will usually discard! Seems usually not worth the effort. Well, it is worth the effort, so we shall see
