I always use dishwasher tabs and boiling water for my glass bongs. This would dev harm metals and i have cleaned aways a lot of ornaments with this but it works like a charm. Just clog the wholes, put 1/2-1 tab in the bong and fill with hot water. Sometimes there are some char like dots left that are easy to remove with a brush.
In austria we have "schmand weg" for cleaning bongs and the tabs are a cheap alternative.
That's interesting.
I use a percarbonate cleanser for my brewing equipment. I'm going to give that a shot.
I would assume that lye would work but that's nasty stuff. Cheap. Cheap nasty stuff.
You'd have to neutralize the base and then rinse the hell out of it anyway.
Maybe I should think about this in the morning