[Jeff]

How would I go about doing it?

[Thor{DoH}]

Frosting glass, not forsting glass, right?

Good question, and can't say I know the answer, but if it were me I'd start by using really thinned down white, like skim milk thin. Get a few layers at that consistency on there and it should start to give if a frosted look.

[deraj]

I would water down PVA glue.

[Thor{DoH}]

Most PVA glue dries clear, no? Any I've used has anyway.

[Nightmare]

Try a spot of Varnish? the Number of tutorials I've seen that has warned of not varnishing clear plastic as it may turn frosty must mean that theres some truth in it.

[Operation Sunset]

A while ago in a class we used an etching/frosting spray (from Plasti-kote, I think) on glass and it gave a good effect. It looks like the spray is suitable for plastic surfaces as well as glass though buying an entire can of spray for, I'm guessing, a small job might seem a little excessive.