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I'd like to whitewash or frost a couple windows with something that
will come off easily in a few years. Any recommendations?

Thanks, Dianna

Not sure what you after. If you simply want
to 'frost' windows for privacy, buy a roll
of the clear shelf liner material from Walmart.
Although it's "clear" it really isn't when
applied to glass. And since it is a low-tack
adhesive it peels off easily when you want.
CAVEAT: It may not peel so easily if baked
by sunlight.

If you want to paint something on the window
that is easy to remove, use ordinary poster
paint. Add a bit of soap to make it adhere
more readily, and also makes it easier to
remove with a simple water washing.