Yesterday I was about to toss all the Plexi scraps I have because the paper
backing is stuck on so tight it can't be peeled off. I decided to try
laquer thinner, assuming it was going to melt the plexiglass since they were
headed for the trash anyway.

I moistened a paper towel with it, place it on the paper backing and a few
minutes later it had softened the backing enough so that I could peel it
free (with a bit of work - the scraps are probably 25 years old).

The Plexiglas appears to be completely unharmed by the solvent, which really
surprised me. I thought would cloud it or melt it. I am now going to try
to figure out the best way to scale up the process to get the backing off
some very large sheets of 1/4" stuff. If anyone's interested I'll post the
brand of laquer thinner and the type of Plexiglas it's working on. I know I
have some Lexan scraps mixed in, so it may only work on certain types of
Plexi.

--
Bobby G.