Removing designs from glass!

[mari-mac1109.livejournal.com]

I found some cool glasses at a thrift shop that I'd really like to etch/frost, but the problem is, these glasses already have colored designs on them! I can't tell how the designs are on there, but I can't scrape them off with a razor blade. I don't know if I'll need to use a chemical solvent and if so, what would be appropriate. I've googled and googled and memory searched, but with no luck!

The designs are the same medium as the Clue logo on this glass:
My glasses do NOT have the Clue logo on them. Just ugly blue and tan flowers. The Clue glasses are just to show the type of material the design is made out of as I do not know what it's called.



It's okay if the glasses get a bit scuffed up, as I plan to etch them anyway.

Thanks!