Three questions. Is there any problem (other than possible fading) with putting epoxy over oil based wood stain? The epoxy will be varnished. Second, Varthane makes a water based outside spar urethane. Is it any good to use? Last, my spars are straight grain douglas fir, and my mast is hollow birdsmout Sitka spruce. Would the spars look better natural, or stained? The boat is okume and mahogany.
Dave
You should not epoxy over an oil based stain. There are water based stains that you can use. Be sure that the wood is completely dry before applying epoxy.Â
Yes, you can put epoxy over an oil based stain. Naturally the stain needs to be well dry before applying epoxy. The WestSystem user's guide covers this and offers testing to document the lose of peel strength you can expect (5% or so, nothing to get excited about).
Generally, I like to tint the epoxy when I'm trying to stain wood. This is the best of both worlds. You get darkened wood and lock it down with epoxy in one shot. Dry acrylic pigments are the usually choice, though a word of warning. If you're haven't done much stain matching, you'll need to practice on something before making a blotchy mess of your boat.
Water born urethanes (there's a misnomer) have come a long way in the last decade, but they're just not there yet, frankly, not even close. Yes, they clean up with water, but the durability, gloss retention, color and finish quality suck big, hairy, wankers. These products are great indoors where the low VOC's are mandatory in today's environment, but if asked to live outside they just make you wish you'd used something else.
I'm a natural wood guy, screw the stain. Stain is for women that just have to have that hideous purplish red color on everything. Some call it mahogany, I call it ugly. Mahogany, in it's natural state for example, has these little sparkles in the grain. It's silica and causes the grain to change color as the reflected light changes. It's beautiful, but once you stain it you lose this quality. A lot of woods are just stunning with varnish on them, then get turned into something else, usually not as pretty, with stain. Then again, that's me.
Are there different rules for different epoxy systems? I'm pretty sure that system three says oil based stains should not be used.Â
Thanks, Paul. I'm actually leaning toward natural wood. Douglas fir gets a little reddish-brown with time, helped by amber varnish, right? What about Varthane's standard outdoor spar polyurethane? Is it a decent product to use?
Dave
All surface stains will limit adhesion to a degree, Chris. It's a function of the stain partly coating cellular walls within the wood. Fortunately, much of epoxy's strength is mechanical in nature, in that the resin fills the cut and/or exposed cells on the material face, then cures, making it well "keyed" into the surface structure. The peel strength can be reduced by around 5% if memory serves me, which again isn't a significant enough figure to get worried about.
Varthane (RustOleum products) has two spar urethanes, their Diamond Spar and their Premium Spar. They also have a professional grade and of the three I have no idea what the differences are, so you may want to shoot them an email. Ask them directly what are the differences between Diamond Spar and Premium Spar, plus ask about the professional grades. Don't ask for a recommendation for your use. This just lets them off the hook and they'll butter your butt with advertising fluff along with "their recommendation". Ask for an explanation of the differences, which hopefully will give you an idea of the market each product is geared towards.