Sealer for non-marine plywood

[PBzeer]

I'm making some oak panels for the interior around the nav desk (for a contrast and to lighten up the area a bit) and wonder if anyone has any recommendations on a good sealer to use after staining. I've got Minwax's Helmsman Spar Urethane in clear satin, but wondered if that's sufficent or if I need something better to use.

Thanks,

[ambianceack]

What you have sounds like a good product, you may want to consider a minimum of three coats and consider doing both sides of the plywood. That is to deter moisture on the back side. Hope that helps.

Joe

[PBzeer]

Thanks, was already going to do minimum of 3 coats, all surfaces, as moisture is my main concern. Also have all cutouts made and holes drilled so as to seal them as well.

[sailaway21]

John,
I have not had good luck with that particular product, specifically regards water. I have a counter top in my entryway that water sat on and penetrated the Helmsman. Didn't raise it-just discolored it. Of course I blamed it on my wife as she applied the three coats! I think the name implies something the product does not deliver.

I would recommend Varethane. It's pricey and not as easy to find, but really holds up.

One other technique I've heard of, but not tried yet, is to coat the wood with west system epoxy and then apply whatever synthetic varnish you wish. The epoxy does the wood protection part and the varnish takes care of the "look". I'd probably experiment with stain, epoxy, varnish on scrap first to see what the end product will look like. Of course the epoxy alone would be fine for unexposed to sight portions. Given that you are using plywood I would soak in a couple of coats to the end grain as that is the most susceptible to moisture penetration. When you drill your pilot holes for your screws you can "butter" each of the screws with epoxy and thereby seal those holes as well.

Good idea on the lighter colored oak.

[Faster]

We spoke to a kayak maker this past summer - produced the most beautifully finished cedar strip kayaks I've seen anywhere.

His finishing method - similar to what sailaway describes - was to use an epoxy coating as a sealant, and then covered it with a UV resistant varnish. The UV protection prevented the epoxy itself from turning milky as it is wont to do if left unprotected.

If this method works for something expected to spend time in full exposure - it should do really well for interior woodwork where the exposure is reduced.

[camaraderie]

John...since you didn't use marine plywood, you really need to have good protection from moisture ingress which can lead to un-gluing. Suggest epoxy on all surfaces first, followed by any finish you like.

[PBzeer]

Since I'm only doing one panel right now and it's vertical....and it holds the stereo , I went ahead with the Helmsman. Especially since I didn't see any of these responses first.

[feetup]

further to Sailaway 21 and Faster regarding the epoxy, you can get even better protection, especially on end grain by brushing West System or Industrial Formulators epoxy and heating gently with a hot air gun to thin the epoxy and to help capilary action to draw it into the wood fibers. This is a technique used to restore rotted wood in areas where it is impossible to replace. Keep the wood warm and keep applying epoxy till it will take no more. The warmth will shorten the cure time as well. Then proceed with the varnish to beautify.
The problem with trying to seal with only varnish is that the wood will "move" with moisture fluctuations growing and shrinking several percent with extremes, and even polyurethanes cannot cope with this much movement after some time has elapsed. the finish will crack microscopically allowing water to enter the wood, not just a shift in moisture content. Epoxy has a very high tensile strength, actually preventing these microscopic cracks. The only problem is that epoxy will turn milky brown from exposure to ultra violet light so must be coated with a U V stable varnish.

Feetup
"Epoxy can be cured!"