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How to remove white enamel labels and graduation lines on borosilicate glassware?

I have a couple of pyrex lab media bottles that have graduation lines and patches of white for labels. I believe this stuff is enamel that is baked on to the glass. Does anyone know of a way to remove the enamel without scratching the glass?


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big16point1 month ago

This was borrowed from brassgoggles.com:

"So, to bake off enamel -

From room temp to 600 F in 10 minutes, no less.
From 600 F to 800 F in 10 minutes, no less.
From 800 F to 1150 F in 10 minutes, no less.
Stay at 1150 F for no more than 5 minutes
Decrease heat from 1150 F to 200 F in no less than 45 minutes
At 200 degrees, item can be removed from kiln/lab oven.

If the enamel hasn't burnt entirely off, it should be scraped off easily at this point. If it doesn't come off by this method, grow to love it - he can't think of another way to get it off without scratching the glass.

Afterwards, the glass is fine for display - if you want to use it for lab work, you'll need to anneal it again.

TEST ON A PIECE YOU DON'T LIKE FIRST!"

big16point1 month ago

i know its an old topic, but I was trying to figure this out. I tried emery cloth/strip sand paper. It scratched the glass, but I was melting that spot for a project and it appeared to have polished the scratches as well. Some have said to bake it off in a kiln. I guess I'll keep trying.

artworker3 years ago
Try using crushed sugar on a scotch tape instead of sand paper. May work!
rickharris3 years ago
if you really really want to remove them your going to have to grind them off, use progressively finer and finer abrasive until you achieve an even matt surface and then polish that back to a gloss.
skyberrys3 years ago
Try gently grazing the white lines with a razor blade, under running water.
Vyger3 years ago
I believe that it is actually fused with the glass so its part of it. Sort of a type of glaze. Painted on and then heat treated to melt it into the glass surface. You would have to etch it off to remove it and then you would be left with the marks of where it used to be.
Kiteman3 years ago
No, that's the point - the markings are supposed to be immune to chemical attack.

Removing them will leave marks on the glass that are larger and uglier than the original marks.
Junkbots (author)  Kiteman3 years ago
What about a mechanical one? I was thinking about using sandpaper of progressively finer grits.
So was I, unless you think you can sand finely enough to leave no obvious mark?