# Too Late for Spar Urethane?



## Rahnefan (May 1, 2009)

I bit the bullet and bought a gallon of spar urethane so that my future mache props might not end up like mush when the rain comes. But what about my other props that are already painted with acrylics? Would it be a bad idea to coat them now with spar urethane?


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## edgTX99 (Sep 28, 2009)

It should work... just rough-up the surface a little. Be sure you want to do this, though, because you won't be able to paint over the urethane later. Even though all urethanes will yellow over time, it won't likely be noticeable unless you're covering something with a very light color. Dark stuf=no problem.


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## Rahnefan (May 1, 2009)

How long does it take this stuff to dry? Props need to be ready for a party on Thursday. Do I have time to apply urethane, let it dry, and then paint them? (nights only of course)


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## Rahnefan (May 1, 2009)

Hey wait wait, did you just say I can't paint over urethane? Why not? I thought that was the idea?


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## grim reaper (Aug 18, 2005)

you use the urethane over the paint like a sealer/varnish if you painted ontop the the paint wont be protected and will most likely peel off the urethane i guess.


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## edgTX99 (Sep 28, 2009)

The problem with the spar urethane is that it's soft & flexible... works great as a top coat, so it can flex with the material underneath. If you paint on top of it, it'll still expand & contract with heat and cold. It will wrinkle the paint on top, enough that it'll eventually flake-off.


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## Rahnefan (May 1, 2009)

I hear you. I am confused because I read Stolloween's instructions which (I thought) said to do this right over the paper mache, before painting, and use a different kind of sealer over the paint.


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## edgTX99 (Sep 28, 2009)

You can use regular polyurethane, just not the spar variety. The regular stuff is much harder and doesn't react with temperature changes so much.

We like spar urethane for outside use *because* it's flexible and can shrink and grow with the temperature swings and not crack. Conversely, the interior stuff, when used outdoors, will crack and allow moisture penetration to the wood.

Paint, even the latex stuff, is relatively brittle, and will crack when applied over such a "fluid" base like spar urethane.

Since you're painting, you're better-off using the kind you'd use on hardwood floors or indoor furniture. Daily, repeated temperature swings and exposure to the elements won't be a problem, so the regular stuff should work great--use lots of thin coats!


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## Rahnefan (May 1, 2009)

Thanks edgTX99.


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