Varnish Delamination

[Ramsgrade]

Got a question for you all. I recently restored my Dads 1940 Old Town Yankee which was a labor of Love and I had never attempted anything like this before. Shout out to all who have posted Questions before me. What a resource. Well the big day arrived and the Yankee performed flawlessly, until I let my unexperienced adult sons go out by themselves. They swamped it and when I took it home to dry out I left it in the yard to direct sunlight. My Bad? Anyway the varnish on the inside on the planking de laminated into bubbles of various sizes. Attached are some pictures that show it. Any Ideas as to what I do now? Thanks.

 

[MGC]

That's a good looking canoe.
That separation is unfortunate.
What sort of varnish was used on it? Was a polyurethane used?
Did you "treat" the hull with a linseed oil before varnishing?

 

[Ramsgrade]

Thank you. I used Epiphanes clear for a number of coats then finished it with Epiphanes Matte finish. I did treat the hull with Linseed oil. I was wondering if the gaps between the planking, because it's so old, allowed water to get under somehow then when I dried it in the sun the evaporation caused the bubbling?

 

[ALCEDO ATTHIS]

I think it's under , you have a few mm betwin the planking , water pass , stay on canvas and enter in wood by this way and cannot escape ... the water dont enter by this way in the warnished wood but now , it want escape , the wood was so dry ... maybe also betwen ribs ans planking , in the crossed part , no warnisch ... you put the canoe in the sunlight ; maybe up side down will be better ? by the sun by the canvas and gravity
but every body have a canoe , and this problem of water , so I dont know about your warnisch

 

[Todd F]

Whatever the solution is, my recommendation is to make your sons part of it. Not a parent advisor, my sons have dorked a few things up. As pissed as I was they are all about making it "right". Good luck with the fix, looks like a really nice canoe.

 

[chris pearson]

Did you use gloss varnish before using the matte? Did you sand in between coats? I think it’ll go away as it dries.

 

[Howie]

I'm thinking that baking in the sun caused something in the wood to out-gas which caused the varnish to lift away in spots. Could have been water I suppose, but I don't see this happening in areas between the ribs.
* I'm wondering if something was in or on the wood before you varnished. I assume you stripped the old varnish off before revarnishing. How did you clean the wood afterwards?
* I'm suspicious of the Linseed Oil - it needs to dry completely for varnish to stick properly. You say you treated the hull with Linseed Oil. Did you treat just the outside or the inside as well? If the latter then maybe you didn't wait long enough for it to dry thoroughly. And what about the sequence of things. If you applied the oil before or between varnish coats then maybe some found its way to the inside of the canoe.
* I suppose another possibility might be that the wood wasn't completely dry deep inside when you varnished. But you'd have canvassed the canoe after varnishing, and the time required to cure the canvas filler should be more than enough time for the wood to completely dry.
* You didn't use shellac did you?, 'cause varnish doesn't stick well to shellac.
* And I don't suppose you were using a spray can of some silicon polish somewhere near the canoe while you were varnishing...?

Canoe looks great BTW.

 

[MGC]

I'm always suspicious about oil inside the canoe under varnish. I like to use thinned varnish directly on the wood inside the hull. I don't put oil on the outside of the hull until the inside is sealed for fear that it may interfere with the finish on the inside.
Eventually the lifted finish will need to be dealt with but for now, it is what it is. Keep an eye on it and use the canoe.

 

[Maxtoon]

Traditional varnish bonds to anything only in one way - mechanically. It requires some surface characteristic to physically key into. This can be the natural porosity of the wood, or scratches from sandpaper. If there is any material deposited on the surface that prevents the varnish from securing a firm hold, then even something like heating from the sun can break weak mechanical bonds and result in film separation. Wood with high moisture content, excessive oils, improperly applied filler/stain, not enough sanding or sanding with too fine a grit (anything finer than 220 grit for build coats) can all be contributing factors. The use of dis-similar materials, like using shellac as an undercoat and varnishing over the top can also result in large area of film lift when exposed to heating from sun light. The two materials have different reactions to heating from sun light, and you can experience the shellac base soften from the sun before the varnish is affected. This can break the varnish mechanical bond to the shellac causing the varnish to peel. The trick is to minimize the shellac film thickness to produce the desired effect and still leave some wood porosity for the varnish to attach to.

 

[Ramsgrade]

Thank you all for your thoughts. Let me answer the questions from the earlier posts first. My sons traveled to see the canoe launch in the water for the first time in more than 30 years. I felt like a Disney ride that day taking family out for a loop around our lake. My brother and I were the only ones who knew how to paddle/steer correctly. The canoe was a hit to all passersby's because you just don't see many in California. Anyway, the questions, I used gloss varnish before the matte and sanded in-between with 220 grit. After the day of canoeing and the day drying in the sun was when I discovered the problem, I let it sit in its sling in the garage right side up for over a month to let it completely dry. I like the outgassing idea I did use a thinned layer of shellac on the inside before a thinned application of Epifanes clear varnish. Always lightly sanded between coats. I also linseed oiled the hull before I did anything to the inside. The linseed oil dried for about 6 weeks. Maybe a bit of the linseed seeped thru but not enough to cause the wide spread problem.. I stripped the old varnish off and sanded the imperfections of the ribs and planks on the inside and cleaned the whole thing with TSP months before I applied anything to the inside. I'm believing that the Shellac maybe the culprit here and if I had just let the canoe dry inside the garage the outgassing melting may not have shown itself at that time.

 

[Howie]

Yup. Shellac. I'm so sorry. I did the same thing once years ago - I had used it to better match coloring in spots. Had to restrip the whole interior. If I remember correctly, shellac has a waxy layer that varnish doesn't stick to even if sanded. You might find that the varnish will lift up if you pull on it with a piece of tape! I believe there is a type of shellac (denatured?) that doesn't have the waxy layer, but it's totally clear (lacks the amber tone).

 

[Maxtoon]

You should be able to get a pretty good indication about where the failures are occurring by opening up the loose layer at the bubbles. What is below the lifted layer? If it is wood, the failure was between the wood/Linseed Oil interface. If there is shellac under the lifting (wipe with alcohol, it will dissolve the shellac and stain the rag), then that is where the failure was between the shellac and varnish. If there is varnish under the lifted area, it could be that you either missed sanding some areas (between the ribs can be challenging) or that you didn’t remove all the sanding dust and it acted as a parting agent. Of course, these scenarios will not always be conclusive, but it is a place to start. In general, surface preparation should almost always take twice as long as the finish application.

 

[Michael Grace]

Shellac comes in its traditional form and in a de-waxed form. The wax in raw shellac decreases the clarity of the finish but more important, it can affect how shellac performs with other finishes. If you use shellac in a mixed-finish plan, always use de-waxed shellac - preferably bought from a reputable source in flake form - because natural shellac doesn't bond well with other finishes. On the other hand, de-waxed shellac is compatible with many finishes (though a baking sun might change our definition of "compatible"). If you do use shellac, best is to make it up yourself by dissolving de-waxed flakes in alcohol so that you are assured you know what is in it. You can actually de-wax the ready-to-use shellac from stores, but it's very easy to make your own de-waxed shellac from de-waxed flakes.

In the early days, many canoe builders apparently used shellac as their initial finish on canoes, but of course we cannot say now how those original finishes fared.

 

[1905Gerrish]

Stripper has lots of wax in it as well. The canoe should chemically cleaned before varnishing. The one time I tried TSP it was useless. I recommend Snappy teak-nu for about the 100th time

 

[Worth Gretter]

missed sanding some areas (between the ribs can be challenging)

I found that Scotch-Brite scrubber pads worked better than sandpaper on the interior, for just this reason.

 

[Ramsgrade]

I did use TSP first after I had prepared the inside by stripper/sanding/vacuuming. Then after washing it out with TSP I did use the Snappy Teak NU.
I just saw on Facebook how someone took a multitool cutting blade, grinded the sides down to fit the spaces between the ribs and then formed the flat side to conform to the canoe curvature. Then applied double sided tape to the curve and attached sandpaper to that. Sounds like an interesting setup to get into the tight areas. Well once the laceration on my leg heals a bit I will get back to the canoe and check the bubbles for what lifted and whether the shellac for sure the culprit. It's all a passion of Love working on something my dad used in the upper Michigan 1000 lakes area to explore way back in the early 1940s before he joined the Army in 43.