Wipe on spar varnish?
I’m ready to finish a doorway casing with two side windows. It’s in expensive fir and has two coats of watco. (It’s not installed in the house yet.)
As a replacement for a north facing slider, it will see just a little direct sun and not too much rain (it almost always comes from the southeast here.)
I’ve been considering using a varathane exterior water based poly but would like to wipe it. Can one wipe these polys?
Also, I’m considering diluting an oil-based spar varnish and wiping like some do with interior varnishes. Will this even work? What spar varnish and what should I dilute it with?
Thanks in advance. This is a vary large project and I haven’t got anyplace to spray it.
Yes, you can thin oil based spar varnishes to wiping consistency, though there is a very big BUT. The UV protection depends to a great deal on the thickness of the total coating. The manufacturers of the best spar varnishes, which never contain polyurethane, generally recommend 6 brushed on coats, with only the first one thinned very much. Since it takes about 3 wiped on coats to achieve the thickness of one brushed on coat you can do the math. There are only three brands of marine spar varnish worth considering. Epifanes High Gloss Clear, Interlux Schooner, and Pettit Captain's. The single part polyurethane in Big Box spar varnishes is particularly susceptible to UV damage. Thirty dollars for a Euro quart of Epifanes will be cheaper over time than $10 per quart spar urethane from the Borg.
North exposures give a chance that the clear finish could succeed. You will still need to do regular maintenance, scuff sanding and applying a maintenance coat about every other year, or sooner if you see any dulling of the finish, especially if you are south of the Mason Dixon line. Patch any dings immediately.
With exposures with more direct sun, I'd strongly recommend paint or opaque stain unless you are a glutton for punishment.
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