Teardrops n Tiny Travel Trailers

Varnish and Epoxy~ a Professional Wood Finish for Teak Part1


Varnish and Epoxy~ Part2

Varnish over epoxy by West System.

When varnish is used alone as a coating, it is constantly fighting two distinct battles. One is to stay attached to a substrate that is expanding and shrinking as the moisture content of the wood changes. Seasonal changes in moisture content occur because varnish is not a particularly effective moisture barrier. When the wood changes dimensions, it forces the varnish to stretch and shrink in order to stay attached. Given enough stretch/shrink cycles, the coating will eventually crack.

The other battle is oxidation from exposure to the sun's UV light, a phenomenon that contributes to loss of gloss and cracking.

Three coats of epoxy followed by three coats of varnish can achieve the same depth and look of twelve or more coats of varnish. Because there are no solvents evaporating away from the epoxy, it builds thickness faster per layer than varnish and it doesn't shrink when it cures. In addition, three or more coats of 105/207 can be applied per day.

More importantly, sealing wood with an epoxy moisture barrier dramatically lessens its stretching and shrinking. Varnish benefits from being applied over a stable substrate. High-quality marine varnish is formulated with UV filters. So, the epoxy coating benefits by getting the protection from UV radiation that it needs. WEST SYSTEM 105 Resin/207 Special Clear Hardener and varnish complement each other synergistically. The two in combination last longer than each coating by itself.

Varnish over epoxy A look at the benefits of undercoating with epoxy is a downloadable pdf. of the full article.

Three coats of epoxy followed by three coats of varnish can achieve the same depth and look of twelve or more coats of varnish.

Or, to quote my former world-class wood-boat-building boss, "epoxy is varnish that can be applied four coats at a time".

Hello! Just doing a little research for my plan of building a woody exterior (sides only). I assume that I will want to epoxy all my wood surfaces, is that correct? I know to pay special attention to the edges that are exposed, like my side walls will be, but what about the plywood skin underneath my aluminum top? What about the 3/4" skeleton in my walls? Do either of these need epoxy since they are covered by another skin?

Lastly, for the beautiful woody side walls that I have imagined in my head, do I stain, epoxy, then varnish with a marine grade sealer as mentioned above? Actually, I didn't watch the videos yet. My staining question might be answered in it!! I will watch it later. Just thought this might be a good place to post my question.

Lauren, The videos are worth watching. Your woodie sides do not require epoxy and or fiberglass. BUT to fiberglass first, then to use varnish will give you a stronger, more abrasion resistant, much more weather/waterproof finish, that lasts much longer. It will require less maintenance later on. Varnish alone might need to be sanded and recoated every year or two.

In general one coat of epoxy will take the place of three or more coats of varnish. You can build up your finish much more quickly with epoxy that is top coated with varnish. Good marine quality varnish is costly. Often over $30 per quart. Epoxy can cost less than varnish (maybe half as much). Epoxy lacks UV protection so it needs to be varnished or painted. Using epoxy (and fiberglass if you choose to) and varnish gives you the best features of both finishes.

There is no need to epoxy under aluminum. It might, if you choose to, add an extra layer of protection against water intrusion if there ever is a leak.

There is no need, IMO, to seal the inner wood skeleton with epoxy. You could do it if you wanted to and that would be a top quality job. However I did use a primer on mine except for surfaces where I would glue the plywood to the frame. There is a primer that also acts as a very effective glue that I want to use to seal the inside framework AND to adhere the foam insulation to the thin plywood skins for extra stiffness. My goal is to over build for strength and to protect against potential rot from water or moisture intrusion when prudent. What some call using a belt and suspenders.

Staining is optional. If you use plywood that is good looking epoxy and varnish will protect it and enhance its beauty. Making a sample board and experiment to find what you like best is a good idea.

Yup, you have it right. We didn't stain, like the natural look. But epoxy, them varnish on ours.

I did end up watching the videos after I posted my questions instead of grading papers like I was supposed to! I figured those would be the answers to my questions. I did like the birch and maple? ply that I saw. I can't remember if it was maple for my other choice. Loved the grain on both. Did stain some already. The epoxy should just be clear, correct? Might it deepen the wood in color at all? I am really leaning towards a stained side. I just figured that if it were epoxied first, then the stain wouldn't take. I will most likely stain, epoxy, then varnish. I know it will be expensive, but if I really want a wood-sided tear, then I better make it look good! Thanks for the input, both of you!

Lauren, the video about varnishing over epoxy was full of good information and not too technical. Hope you enjoyed the distraction from grading.

I had a bad experience with staining. I foolishly/unknowingly used an oil stain and a water based varnish. The varnish did not "stick" well. It was a pretty big set back. My local paint store said "Why are you going to stain birch plywood when it will look beautiful with varnish?" They were right. Its much easier too (less $$, time, and effort). Better to spend a little more on beautiful plywood and le$$ on stain and or varnish, etc, imho.

Raka.com epoxy may darken wood a little. Mostly, it enhances the color of the grain. The effect is similar to wetting the wood with water. Doug Hodder has more expertise with stains and gels, etc. He's a good guy and often very willing to share his ideas and experience. It might be good to PM him. Maybe exchange phone numbers so you can talk. Or post a question about staining your sides then using epoxy and varnish and see if a good discussion develops to answer your questions. There are dry powder stains that resist fading better than liquid stains. Doug is the one who first wrote about them here, afaik.

GOOD LUCK

Fiberglassing a Strip Built Kayak shows fiberglassing techniques and how it enhances the beauty of wood and wood grain:

I don't think the Raka epoxy darkens wood as much as the epoxy used in this video. Different epoxy formulations will vary in their transparency. Epoxy transparency samples