Stacy DeRuiter's test of polyurethane spray
I found some plywood scraps in the trash and coated them with clear polyurethane spray. I made this little mobile, and treated it badly...

My rating of this material: It does what it is supposed to do. I coated a little wooden mobile with it, then I left the mobile out in the snow overnight, and then I let it sit in some water puddles for a few hours. The mobile looked exactly like new after this treatment; not wet inside and with no water stains. This is a really easy way to finish wood if all you want is a little layer of is supposed to work the same on metal, but I didn't try that.
--Stacy DeRuiter, Dec. 11, 2005