Do you have any experience in rolling and tipping with System Three WR linear polyurethane paint? If so, what results have you experienced? I continue to have brush marks, no matter what I try. I'm painting over a mahogany-epoxy base, but it's not working. Can you help?
Don Casey responds:
I don't have any experience with System Three linear polyurethane, but I can offer you a list of guidelines that will help you get the best flow characteristics with any kind of linear polyurethane paint.
1. You absolutely must have cool, dry weather when you apply the paint. High humidity causes the paint to kick before the flow-out process can be finished. This is the biggest obstacle to getting a perfect finish. So hold out for a day that's not warmer than 75 degrees F with humidity that's lower than 50 percent.
2. Don't paint in direct sunlight. The radiation has the same effect as heat, causing the paint to kick too quickly.
3. Use a really good brush. You need a top-quality badger-hair brush. You will not get a stroke-free finish with a cheap bristle brush or with a foam brush.
4. Keep thinning while you paint. The thinner the paint is, the better it will flow. Until the paint runs or sags, it is not too thin. There is a caveat here and that is too much thinner robs the paint of gloss as it flashes off, so you cannot go beyond the max listed on the can. This is yet another reason to paint in a cool, shady area if you can.
5. Do a test application without tipping. This guarantees no brush marks. For light colors, a rolled finish typical dries to a slight "orange peel," which is a very acceptable finish to a lot of boatowners. I don't know how a clear finish will do, but try it.
6. Back up and have a look. If you don't see the stoke marks from six feet away, no one else will even notice them.
As for other brands, I typically use Interthane because it is formulated for the roller application, but you should be able to coax a near-perfect finish out of almost any brand. Good luck.