- Mon Jun 01, 2009 9:35 am
This is a very good subject...one that even with all my experience I haven't fully resolved. What we look for in a varnish is UV protection, durability, scratch resistance, ease of application, appearance, and economics. Basically that means you will use a urethane spar varnish.
The high solids, oil based, urethane spar varnish is the most economical, most durable, and easiest to apply varnish that most of us can use. The only problem with the oil based urethane is that it darkens the wood--as the sales people say, "...it gives the wood that rich amber glow...". This is fine and good but in many cases it makes the wood appear muddy after a time. I don't like that. If I could find a high quality, oil based, urethane that stays crystal clear I would use it. I haven't checked all of them--and I'm closely watching Darrell's finish to see how it holds up. So--if anybody finds a good oil based spar varnish that doesn't darken--LET ME KNOW.
I've been using Varathane, water based, exterior urethane because it stays crystal clear--never darkens. It's more difficult to apply than oil based stuff. You WILL get brush strokes. But that's ok. You can keep applying thin coats, sanding between coats, until you get a nice coating. Then sand smooth and buff. For what I call a utility finish, I can do fine with a minimum of sanding and buffing.
2 part urethanes are another thing entirely. They can be acrylic or polyester based. Polyester based is the best. The 2 part urethanes are generally out of the range for most of us unless we have very special needs.
And the UV protection in urethane degrades after a time. For best results you should recoat your boat at least every two or three years.