Greetings all –
I’m making an exterior door for a fireplace wood bin – exterior access to an interior bin. The door is composed of a 1/8″ thick double faced aluminum composite panel (called Alucobond, it’s an exterior building cladding material). This has been epoxied to a 3/4″ plywood panel and the edges of the aluminum were scored with a 45 degree router bit and folded up to make a pan affair to conceal the plywood edges. These ‘flaps’ were also epoxied to the plywood. So now, the only exposed wood is the back of the plywood which will be fracing the inside to the wood bin.
Unfortunately due to the exposure where this door is located I can’t eliminate the possibility of blown rain or rain runnoff down the outside of the fireplace (brick) from finding its way around the four sided frame and stops of the door frame. Thus I applied a coat of West Systems epoxy to the back in an effort to seal the whole thing.
So – the question is …. is a single coat enough? I put masking tape all around the edges leaving it stick up above the surface of the plywood to prevent runs over the edges then applied the epoxy in a relatively thick coat. Even before this coat has cured I can see areas where it has soaked into the plywood rather well. Would a second coat be in order and …. Put this coat on this evening, could another coat be applied tomorrow with assurance it will bond completely. Would sanding be better or perhaps softening the first coat a bit with acetone or ….? to be confident of good second coat adhesion?
Thanks a bunch.
From Beautiful Skagit Co. Wa.
Dennis
Replies
It was years ago, but I built two canoes using West System epoxy and I used multiple coats. I cannot remember the details of surface prep between coats, but I do remember that the people I talked to at the company (Gougeon Bros) were very helpful and knowledgeable.
If it doesn't look even, I think a second coat wouldn't hurt. If I remember correctly, we sanded between coats. You typically have to add a coat of UV protective Poly over the top to prevent the epoxy finish from turning milky. Since your surface is not exposed to the sun, it probably won't matter. On the other hand, it couldn't hurt to add the poly.
Since it has been over 15 years since I used the product, I would recommend calling the company to double check. Good luck.
Craig
Thanks, Greg. Did you use any fabric on your canoes?...........
From Beautiful Skagit Co. Wa.
Dennis
Dennis, I have not used gougeon brand in a long time either, but I do remember that that brand creates a wax film on the surface called amine blush, which needs to be removed before the sanding and applying the next coat. It seems to me that you just use soap and water followed by clean paper towels to dry and clean up any diluted residue.I don't think I would use acetone at this early stage in the cure process.
A funny thing about epoxy is that you could have put a second coat on over the first while the first is still soft, because you will get good cross linkage, although I am not sure where the back end of that window of opportunity is. Epoxy holds up well under wet conditions, but breaks down rapidly in sunlight. It sounds like you are OK here, unless there is some over-hang. Dark paint is better than clear for this purpose.
Yes, we used the fabric (6 oz) on both the inside and outside. In some places we even put double layers. This was overkill, but our canoes are incredibly strong (and rather heavy). This is part of the reason that I know we used multiple coats. After the first coat, the weave of the fabric was still visible and you could feel the texture. By applying additional coats, we were able to make the finish completely smooth and clear.
Craig
Dennis, you might try these guys: http://www.smithandcompany.org/ for future reference. Now that you've put a coating of West on the ply it won't take CPES. They get high ratings from wooden boat people (not universal, of course, LOL)
2 coats of epoxy is better. It should keep the water out.
Cover with a good varnish with UV protectors to protect the epoxy.
Hi Dennis. Another canoe builders advice here. The epoxy soaks into the wood and where it is dull you do need another coat. You could have applied the second coat without sanding within a short time frame of the first but that is dependant on temp and humidity. You will need to sand now to get good adhesion and I am certainly no expert but I think the acetone is not the way to go. Epoxy, for the incredibly strong substance that it is, breaks down when expossed to sunlight, so if you think this is an issue you will need to apply a varnish with UV protectors in it. Good luck and don't get it on your skin. P.S. It is not recommended to clean epoxy off your skin with any type of acid like vinegar because it forces the chemicals into your skin.
Most of the advice is accurate, but I'd like to clarify the warning about epoxy on your skin. Cleaning it off with vinegar, which is a mild acid, is fine. It will stop the curing, and help get the epoxy hardenr into water. Detergent and elbow grease are also useful. Acetone should be avoided on your skin. While it is not very toxic on its own, it will transport nasties through your skin into the bloodstream, so cleaning epoxy off your hands with acetone is like injecting some of it -- not good. (Yes, there are solvents worse than acetone for this. DMSO is much worse.)If you want detailed information on epoxy, check http://www.systemthree.com and read the free epoxy book. Info on coats needed for water protection, and UV stability, are likely to be similar for most boatbuilding epoxies.edit: I fixed the URL given.
Edited 2/3/2005 11:08 pm ET by AlanS
Hi Alan. Years ago, 8 I think, I built a cedar strip canoe using West System Epoxy. I had some questions and I called Gougeon Brothers who recommended that you do not clean the epoxy off of your skin with vinegar for the exact same reason as acetone. It will thin the epoxy and get it into your bloodstream. Maybe this has changed I am not sure but I sure do want to build another canoe!
Peter:While I would not expect vinegar to add to the problem of epoxy on your skin, it's not good to have contact with epoxy, and I have not measured the effect of acetic acid. Epoxy and vinegar on your skin are not good -- but I think they are less bad than just epoxy. Perhaps we can all agree that the best approach is to prevent contact of epoxy with your skin. It is toxic, and some people develop bad allergies to it. I try not to wash it off of anything: I discard rollers, brushes, cups and gloves, and break the hardened epoxy off of plastic squeegies, bowls, and other containers.The canoe I made in high school over 30 years ago was redwood/glass/polyester, not epoxy. While it's in OK shape still, the one I made recently with my son using cedar/glass/epoxy is much nicer, and was lots of fun to make. That's what got me back to woodworking after many years.
What type of canoe did you build? I made a 16' Chestnut Prospector. I still have the forms because I REALLY want to make another. Peter
My canoes have both been Minnesota canoe association designs. I don't recall the name of the first one, but it was the original MCA design, with a 17' symmetrical design. The second was an 18' BWCA cruiser.
I use waterless hand-cleaner to remove any that I get on any uncovered skin. Everyone does not have an alergic reaction to epoxy.
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