Rolling and TippingBy Don Casey
Revised by BoatUS editors in April 2012
I have been applying linear polyurethane paint with the roll and tip method for more than 25 years, yet I am still astounded every time by the results. The one word that comes to mind is magic.
The key to getting a flawless finish is the thinner. Too little thinner and the surface shows brush strokes; too much thinner and the paint sags or runs. You have to sneak up on the proper mix. Start with the paint manufacturer's recommendation, then test the mix on a glass panel--window glass, not fiberglass. Using a foam roller, roll some paint onto the test panel, then tip it out by lightly dragging a dry badger-hair brush horizontally through it.
Give the surface a couple of minutes to level out. Because you have painted glass, all flaws are in the paint. If you see brush strokes--the usual result--add a capful of thinner and test again. Stop adding thinner when the stroke marks disappear. Adding paint, because you have to mix it, is more troublesome than adding thinner, so try not to go too far--evidenced by a sag or run.