I have some wood that I want to apply varnish to. My garage is exceptionally dusty and my house is pretty bad too. My question is, is it okay to apply varnish outside in the sunshine? Will it still cure properly because the sun is now quickly drying it off.
Note: I'm actually using spar urethane. It's for a sign.
Best Answer
Urethane doesn't "cure". It dries as the solvent (which may or may not be water) evaporates. It isn't like masonry where time and moisture are critical.
There's no problem applying urethane in the sun other than the challenges it poses to the actual application. Very quick dry times mean less time to get good coverage and work out runs.
Never apply heavier than a minimal thorough coat. Apply liberally, then spread well, leaving just barely a glossy appearance. Multiple thin coats are much better than heavy coats, which will sag and run.