Ring marks on black glass coffee table

[Smowball]

I bought a really nice nest of tables in black glass. There is coasters for cups/glasses but one of the kids(or adults) has been putting them down directly onto the glass and it now has ring marks which will not move. They arent even from hot drinks but cold! I assumed normal glass cleaner would work but no, nor polish, nor white vinegar. They are now covered in all kinds of spots,ring marks and look absolutely awful. Any ideas how I can get at least some of the markings off?

[AlBags]

So it must be coated in something?

[Old_Geezer]

Well I can't believe it is caused by the glass changing, it has to be something stuck on the surface. Can you scrape with your fingernail and see it if scratches off ? Fingernails are not going to scratch glass. If it comes to that, unless the glass is coated with something, you could probably try a metal knife blade, with care.

[Smowball]

there is nothing ON the surface of the glass - the whole colour of the actual glass has changed, its almost as if its absorbed the cold, or liquid or whatever from base of glasses and changed.

[Old_Geezer]

If the glass truly has changed somehow, then I think you're ... out of luck. Can only suggest either replace the glass, or put cups down all over it to make a pattern. No way would you be able to reverse the change in the exact position it occurs. Are you certain the glass isn't coated with something and that has changed ? If so, maybe that could be removed.

[Philtaz]

When I served in the Army any marks on glass/mirrors were usually removed with (oddly) a bit of Brasso and elbow grease.

[Philtaz]

..if Brasso not available Duraglit is just as good.

[scotman]

I'm with OG on this. Uncoated glass should not permanently mark from cups. I think there must be some sort of surface treatment on the glass.

[Smowball]

I will try and post a picture but I do agree its very odd.