Wax recommendations for temporary shine/protection on glass (polyester resin) mahogan

[Olaf]

I have a 25+ year old strip canoe (built by my Dad, with some help from the teenaged me, from Hazen's plans), glassed mahogany (polyester resin), that has a lot of scratches and general roughness and needs a smoother, shinier surface. None of the scratches compromise the integrity of the glass or the hull, but some rock scratches are pretty deep. Lots of wear on the hull from rubbing against the metal legs of a dock.
It has, in its lifetime, had coats of varnish and wax, but none since about '91, after which it hung underneath my parents' deck for about 15 years.
I have washed it thoroughly, sanded the outside lightly with very fine sandpaper, washed it again, and cleaned the whole thing with a soft cloth and acetone. I don't think there's any finish on top of the polyester now (there really wasn't any, even before I did the above).
I plan to sand it (carefully!) this winter/next spring and put on a coat or two of epoxy, along with replacing the gunwales--they are pretty ugly after all those years unprotected.
In the meantime, I want it to get it looking better for the rest of the summer and the fall, and I expect that a more uniform surface will also paddle a little better (even if I won't be able to tell while fishing).
It needs to be ready to paddle in varying wilderness conditions in a week and a half, so I think for now I want to just wax it. Then in the winter I will strip the wax and clean it up for the addition of epoxy.
I've read a lot about the evils of silicone in wax, so I tried finding a paste wax that didn't have it. Couldn't find anything that was clearly labelled as such.
So: can anyone give me a specific brand name of a wax that will make for a good finish, be relatively easy to remove completely in a few months, and not have any negative effects on the future application of epoxy? My searches here and on the web in general haven't led to any definitive results.
Thanks!
Olaf

 

[Todd Bradshaw]

First of all, take it easy with the acetone. It tends to dissolve polyester resin and you're asking for trouble using it as it may leave the surface gummy. You would be better off doing your cleaning with something like naptha, which will clean without attacking the resin. Any wax will likely be a very temporary solution, but one of the best would be Zymol. It's about $12 per bottle and often available at places like Target in the automotive department. I have friends who are world-class guitar refinishers and one reason they use it is that it can be cleaned off later without leaving something on the surface that will cause refinishing problems. It's also water-based, unlike most waxes, which are solvent-based. The solvent in typical car wax is there to dissolve previous layers. With Zymol, you can actually build up multiple layers for a deeper wax job without it dissolving and removing the lower layers as you do so.

The idea of eventually adding a couple coats of epoxy resin to an old polyester stripper is rather controvercial itself. If the polyester and fiberglass layers are still structurally sound, some deep scratch filling with either polyester or epoxy resin, a light sanding and two or three coats of a good marine, UV-filtering varnish is all the hull should need. Re-coating with epoxy would just be adding excess weight and a lot of work to the project. If the polyester isn't structurally sound at this point, adding a couple coats of epoxy resin is not going to fix the situation.

 

[Olaf]

Thanks, Todd. I'll look into finding Zymol.
I did try to go easy on the acetone. It was recommended to me as a way to get rid of remnants of old finishes. I didn't know it was trouble with polyester resin specifically, but I don't trust that stuff--I've seen what it does to some plastics. I once discovered that I was no longer wearing gloves--only bracelets--after working with acetone for a little while.
I'd be happy not to do the epoxy, but have read of people doing it and thought it might provide a long-lasting, stable finish.

 

[Todd Bradshaw]

While epoxy resin is tough stuff, its ability to be long lasting is much more a matter of what's on top of it protecting it from UV. As little as a couple hundred hours of sunlight exposure is enough to begin breaking down most of the popular boatbuilding epoxy formulas. They may yellow, chalk, get rubbery, peel, etc. and will lose their strength and ability to do their job in the process. It is absolutely critical that these resins be protected with a good UV filtering varnish (or paint, which is an excellent UV blocker). UV absorbers generally protect by converting UV to heat, so that it can dissipate, rather than damage the finish. As they do, they get "used up" and so it's a good idea to occasionally give strippers a light sanding and a fresh coat of varnish if they've had a fair bit of exposure. Like just about any canoe, the damage is more likely to happen during storage than when the boat is actually being used, so storage out of the sun is a very good idea.

You will also probably find that despite the fact that it doesn't stick to wood very well and is not as good as a moisture barrier (making it inferior to modern epoxy resin for strip building) the old polyester may actually be more scratch-resistant than new epoxy resin will be. Back in the dark ages when Norm and I started making strippers, we used polyester resin, as it was all we had at the time. Switching to epoxy when it became available was a good thing from an adhesion and workability standpoint, but rock-for-rock, scratch-for-scratch, it was pretty obvious that it would scratch more deeply, given the same impact. Since the adhesion situation on your canoe is already a matter of the original polyester to wood bond and not going to change, adding epoxy on top may just be adding a softer, more scratch-prone layer to the surface, when all the boat really needs is some touch-up filling and a few coats of good varnish to look about as good as it's going to get. Varnish isn't likely to fix cloth fractures (small spots where the impact has caused the white-ish weave pattern to show) but neither will new resin. To fix them, you basically need to remove and replace the damaged cloth in that area.

We're assuming here that you don't have any delaminated spots. They would show up as small bubbles where the glass is no longer stuck to the wood. They'll usually be kind of white-ish - green-ish, maybe blue-ish or even pink-ish, depending on what promoter was used in that particular polyester resin formula. You can often press on them with a finger and see the glass flex. These are potential big trouble spots and should either be cut out and patched with new cloth or possibly injected with resin to fill the void. Epoxy resin would be the most logical choice for this sort of repair (better adhesion to old polyester than more polyester has, and no shrinkage). Large areas of delamination would tend to indicate that the best eventual approach would be to strip off the old fiberglass and re-glass the hull with epoxy. This, however, is a big, expensive and nasty job that can be nearly as much work as building a new hull. In many cases, it's just not worth doing and you're better off starting over with new wood.

 

[Olaf]

Thanks!

That's great info and has probably completely changed the course I was going to take with this boat. Thanks a lot for being so thorough. I've worked with wood for decades and can generally rely on my instincts and knowledge, but my fiberglass and resin experience is pretty slight and my knowledge of the various properties is even slighter. Some of it was even dead wrong, I see.