Well, here is what I got off of Marvin's pinball website. I wonder if it would work on silkscreened plexi artwork? If anyone has any thoughts, please post them...
Introducing Krylon's Triple Thick.
In about 1997 I started using Illinois Bronze/Krylon's "Triple Thick Coating" to save backglasses. This is a spray product, much like Krylon's Crystal Clear, but it produces a much thicker film with far less coats. Krylon calls it a "glazing product", but only because of the film thickness produced. Triple Thick is essentially a thick filmed acrylic lacquer. This makes it ideal for backglass preservation. Most backglasses are silkscreened using inks. But after the ink is applied, the manufacturer's usually put a lacquer type coating over the inks to "lock them down". Because Triple Thick (and Krylon's Crystal Clear for that matter) are a similar product, Triple Thick works very well to lock down delaminating backglasses, and does not have the bleeding ink problem that Crystal Clear has.