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ContinuousWave: Whaler Repairs/Mods
|Author||Topic: Wood Finishing|
posted 04-16-2004 11:27 AM ET (US)
I've got a question for Outrageman, or any other wood finishing experts:
I'm finishing two new mahogany seating benches for my 13'. Having been urged to apply the first two coats as epoxy resin rather than varnish to the bare wood, I'm having some issues while sanding that first coat of epoxy. The tiny air bubbles that developed while the epoxy dried seem to be filling up with dust when I sand. I'll wipe the wood down with denatured alcohol to get most of it off, but the air bubble holes still retain some of the dust. Is there any way of removing these tiny white "dust" spots without having to sand down so far that I'm reaching bare wood?
posted 04-16-2004 09:02 PM ET (US)
I would suggest a good vacuum cleaner with an upholstery brush.
posted 04-16-2004 09:47 PM ET (US)
Unfortunately if you don't take things down past the bubbles, you will just have problems later on. This is one of the reasons why I don't use epoxy for the sealing coats.
The problem here is that even if you do get the dust out of those craters, you will have to fill them with finish to get a level surface. It is my opinion that you will never get a complete enough cure of the varnish in them (spar varnish never completely cures that is why it is so flexible).
My advice is to sand it back down, use the epoxy as a glue like it was intended and use 1:1 thinner and varnish for the first two coats to seal the wood.
posted 04-17-2004 08:36 AM ET (US)
I just finished using some West Systems epoxy (not for the same purpose you are referring)
After studying the West Systems information, I never realized that there is a special hardener for wood finishing. Hardener 207 is supposed to be more self-leveling with less tendency to form bubbles. They still recommend a good quality UV inhibitor varnish over the epoxy.
Is that what your using? Or are your using a different epoxy system?
posted 04-17-2004 11:42 AM ET (US)
I agree with Outrageman.
I built a new RPS for my Sakonnet and followed the instructions on the can of Flagship varnish and put on the first two coats thinned 50 percent. I tried some epoxy on a piece of scrap and didn't like the darkening of the wood.
Also extremely important: USE A FILTER when transferring varnish from the can to a paint bucket.
I found that disposable foam brushes do an excellent job.
Bob on Tampa BAy
posted 04-17-2004 02:51 PM ET (US)
Epoxy as a sealer can work very well, but it's got to be applied right. Make sure you are using the right epoxy, so it is thin enough to self level. When mixing the hardener and resin, don't agitate is so much that you introduce air. This is most likely where the bubbles came from. I have had good luck with MAS epoxies for this type of application, because the cure slowly and you have plenty of pot time so introduced bubbles can be allowed to float up. Finally, when applying the epoxy, use an epoxy safe foam roller, and tip out bubbles with a foam paint brush. You will still have to sand, and I'd do the final sanding of the second coat wet to put a nice level finish down under the varnish. Here's an example of the finish you can get using this method:
posted 04-17-2004 10:40 PM ET (US)
There is a trick you can use to pop the bubbles. I taught high school woodworking for 18 years and sealed quite a bit of stuff with epoxy (regular consistancy, thinned, table top resin an so forth). As soon as you finish applying the epoxy stand by with a hair dryer (one with a low setting) and when you start seeing bubbles pass the hair drier over the area. Start about 10 to 12 inches away at first and work in closer if you need to. The bubbles should burst as the air within expands with the heat. Don't stay in one spot very long as it dosen't take much heat, and excess heat can cause the epoxy to set up to quickly. On more porous woods more bubbles may appear so stand watch. As an example of how little heat is needed, the same thing can be accomplished with your warm breath. Exhale (with your mouth wide open) from about 5 to 6 inches away and the bubbles will also pop. I had always used the breath method until I was faced with the task of finishing six classes worth of student projects at the end of one year. 120 cypress slab clocks, all end grain, with table top resin. It was like the Lawrence Welk show. The hair drier saved us all from hyperventilating.
posted 04-18-2004 11:52 AM ET (US)
The Kayak looks great :-)
posted 04-18-2004 11:33 PM ET (US)
Try Sikkens Cetol. It is not rocket science.
posted 04-19-2004 09:32 AM ET (US)
Thanks for all of the input. I have been using the West System 207 epoxy to build the first 2 coats with, then I will apply a quality varnish over the epoxy. After sanding some more over the weekend, I got most of the little "dots" out of the wood. The problem, I have found, is that my wood is so old and has some cracks that run to the edges of the wood. The epoxy does a good job of filling and sealing these cracks, but the air that the epoxy forces out results in a bubble, which collects with dust upon sanding.
The good news is that the few dots that were left were not noticeable after I put a second coat of epoxy on the wood. A buddy of mine, who works with a reputable boatyard, advised me to build with the epoxy rather than varnish - just to make the wood really sealed and virtually maintenence free. Thanks to the West System products, my wood is now as durable as it ever has been - very happy with the outcome. On to the varnish...
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