3 ms·Sorry I believe it was copper etching maybe, probably not glass. Been a while...by idnexjwnfodnn 1mo agoSorry I believe it was copper etching maybe, probably not glass. Been a while...tbrownaw 1mo agoI'd think copper would mean ferric chloride, which isn't that bad.ahoka 1mo agoOh fun, we have used it in school to etch PCBs. Right outside of the class room with no protective equipment of course. It was in a bucket.