Varnish on WRC?

[farmerbw]

All, We've made some outdoor plaques/signs from WRC . I've put 3 coats of Zinsser Bulls Eye Spar int/ext Varnish on the top and sides but not the back hoping that it would make them a little more weather resistant and protect the stain/paint. I didn't apply any to the backs cause for some reason I thought it would "breath" better and maybe decrease movement that might cause cracking on the face. I'm sure this probably wasn't a good assumption!

I read the other day that varnish or poly shouldn't be used on WRC intended for exterior usage because it wouldn't hold up and would peel and crack. Can anyone confirm this is valid or suggest a different top coat that would offer better and longer protection?

I've added some pics and the Play Park one was top coated the same way and has been on our kid's playset for about 4 months now and it still beads water and looks the same as the day it was hung, except for a spot that a woodpecker decided to taste.

Thanks,
Brian.

 

[DaveO]

Brian very few if any finishes will last long in an outdoor environment on any wood including ERC. There is nothing special about ERC that would exclude any finish schedule. Any film finish will eventually peel on an outdoor piece. It is best to finish all sides of the piece for completely the reason why you didn't. You don't want the wood to "breathe" at different rates. The unfinished side of your plaques is going to loose/gain moisture at much greater rate than the finished side will, and that is what leads to warping and cracking.
Studies have found that a clear paint is going to be your longest lasting clear outdoor finish, maybe getting you 5 years. Next would be a high quality marine varnish. The biggest problem with film finishes is that to repair them they will be to be removed. A penetrating oil finish will be the least durable outdoors, but is the easiest the re-finish when needed (every 1-2 years).

MTCW,
Dave

 

[farmerbw]

Dave, thanks for the response. Unfortunately it was pretty much the the type of feedback I was expecting. :BangHead: Guess I'll go ahead and coat the backs and even things out.

Not familiar with clear paint, you have any experience with any particular brand?

Thanks,
Brian.

 

[Howard Acheson]

>> Guess I'll go ahead and coat the backs and even things out.

You want to avoid any polyurethane, urethane or poly if the item will be exposed to the sun. The UV in sunlight rapidly causes poly to deteriorate. It gets cloudy, turns yellow and begins to peel.

I recommend you get a real marine spar varnish. Go to a marina or marine supply store and look for brands like Interlux, Wolsey or, best of all, Epifanes. These finishes are expensive and you must put on the number of coats called for on the label.

 

[farmerbw]

Howard, thanks for the feedback and brand recommendations. I'll check into them next time I'm near a boating store but it sounds like they all may be higher in price range than I was planning on going and maybe a tad more labor intensive.

Thanks again to all who responded. :gar-Bi

Brian.

 

[Howard Acheson]

Howard, thanks for the feedback and brand recommendations. I'll check into them next time I'm near a boating store but it sounds like they all may be higher in price range than I was planning on going and maybe a tad more labor intensive.

Brian.

In the case of finishes, you get what you pay for. Good finishes, particularly ones that stand up the longest outdoors, are not cheap. You won't find them in big box consumer outlets. Also, UV protection is a function of film thickness. The thicker the film, the more UV will be absorbed before the finish loses it's protection. Be sure to follow the directions as to number of coats. 6-8 coats is most often recommended. Finally, UV inhibitors are used up as they work. When the finish begins to get dull, you will have to lightly resand and apply a couple of more coats.