Finishing Prep

chipfitzgerald

Curious about Wooden Canoes
I'm at the stage where I'm ready to start finishing the interior of my OT Charles River. What is the consensus for wood preparation prior to the of applying the multiple coat spar varnish? I've read some people use linseed oil or linseed oil blended with this and that while others simply use thinned varnish. Regarding thinned varnish, has anyone had experience using Danish oil?
 
Danish oil aka Watco, aka, Fornby’s is basically a mixture of oil and varnish probably with some thinner and Japan dryer thrown in. It is primarily used as a furniture finish. I personally prefer an initial coat of orange shellac. Almost any finish, especially varnish, bonds to the shellac. The shellac gives a very nice warm color to the ribs and planking. Not sure what the advantage of an initial coat of Watco would be.
 
Years ago I worked on a canoe for a customer who subsequently finished the interior with Deks Olje. Looked great, but I don't know how it held up in the long run.

It is hard to go wrong with the simple schedule of sanding the interior to 220g, first coat of good, traditional spar varnish thinned 50%, second coat thinned 75% and the remaining coats thinned 90%. Use the manufacturers recommended thinner.
 
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Maybe I wasn't clear... I read about people applying a "canoe soup" before starting the finishing process. What works best for the canoe soup? Would Danish oil work for this step?
 
Never heard of canoe soup. You may be thinking of applying linseed oil to the hull and interior.
If so, a search of this forum for “linseed oil” will give you all the info you need and a whole lot more.
 
Several years ago at Assembly there was a forum of canoe builders, one of whom was Geoff Burke, and it was from him that I heard the term 'canoe soup' used. What he said basically was that he applied sufficient coats of canoe soup (maybe gunwales, decks, etc. but probably not entire hull, I'm not sure) until no more would be absorbed in a reasonable time. The recipe he gave for canoe soup or boat soup was turpentine 3/ boiled linseed oil 1/ spar varnish 1/ tung oil 1 parts by volume.
I have used this on maple gunwales, decks, thwarts and like the way it handles, but you can't be in a big hurry. It takes time to soak in and will remain sticky for several days. However, don't leave it as a final finish, or black fungus will get on the wood. Finish with a few coats of spar varnish, as usual. If I have miss-stated what Geoff said, I hope he jumps in here and corrects me.
 
You might be confusing operations.

For years the prevailing thought was to soak the wood in a mix of linseed oil/thinner, but that was to put "life" in old, dried out wood, not as a prep for varnish.
The current thoughts on this are mixed.

As for prep'ing for varnish, IMO, it's tough to beat what Dan said above.

I am intrigued with the suggestion of using shellac as a base.

BTW, in other circles, boat (canoe) soup is used for preserving the wood from rot, and in addition to the items listed above, coal tar is also mixed in.
Unless you want a very dark canoe, I wouldn't recommend it. :)

Dan


What is the consensus for wood preparation prior to the of applying the multiple coat spar varnish? I've read some people use linseed oil or linseed oil blended with this and that while others simply use thinned varnish.
 
If I wanted to prep with oil, I would use Deks Olje #1, following the directions on the can for applying multiple coats, wet on wet. It will be dry in a day or two, unlike linseed and it doesn't turn back in time like linseed oil can and does. However, I'm not at all convinced that such a base for your varnish is a great idea or likely to be an improvement. I once had an Old Town Trapper in my store and wasn't thrilled with the interior finish on this particular canoe. I called the factory to complain and was told that it had the "usual" schedule of finishing for all of their wooden canoes - one varnish coat thinned 50/50, followed by two coats at full strength. Granted, you can certainly improve the cosmetics with a couple more coats than they used, but in general, that scenario worked pretty well. I don't see much reason to do something different or add additional materials to the mix. As for thinning, heavily thinning the first coat is to improve penetration a bit. Thinning following coats should be done if and when it is needed to improve the way the varnish handles - on that particular day and in those particular conditions with that particular brand and type of varnish. If the brush is dragging and the stuff isn't flowing well, by all means, adjust it a bit, but it is better to adjust paint or varnish to the job as needed than just blindly or automatically.
 
I'm with Dan on this but I also am with Andy. Depending upon the hull I will either use a thinned varnish for the first inside coats or I will use shellac. Rushton was known to use shellac on rush orders as a base and also on rush orders. These first coats are followed by multiple coats of good quality spar and again, depending on the hull are followed by one final coat of Epifane Matt finish...I don't like old hulls to be so shiny that they attract crows.
"Boat soap" so called is applied to the outside of the hull. Everyone has their own recipe. This has been discussed here often..search and you will find many opinions and blends.
I use a blend of linseed oil, turpentine and mineral spirits. I apply it while it is hot. It will soak in immediately and then cure in 24 hours. If you apply more it will not soak in as well and may take a while to cure...moderation is a good idea. I have never seen this blend blacken.
 
Just to be clear, the boat soap concoction is only to be used on the outside of the hull and not necessary on the inside of the hull? If so, which is typically typically done first? Is the inside of the hull spar varnished first then the outside of the hull treated with the boat soup concoction or visa-versa? Thanks for the help - everyone!
 
Keep in mind that when talking about boat soup (as used by Geoffrey Burke), that it is being used to pre-finish the interior of lapstrake canoes and boats. When the shell comes off the molds, a gallon (or more) is poured in the shell and sloshed around, the goal being to saturate the laps and get finish on the interior before the ribs are installed. Final finish is applied after woodwork is complete. Geoffrey, being an Epifanes man, uses either their varnish or their Wood Finish Gloss/Matte.

If you are going to oil the hull of a wood-canvas canoe (whether with BLO, tung oil, or boat soup), it typically goes on the exterior only. Frankly, I've seen no real benefit to oiling the exterior, so I don't do it anymore.
 
I put the boat slop on the outside of the hull after I have varnished the inside of the hull. I do not use it inside the hull. There (as per my earlier post) I will either start with shellac or thinned Epifane. The reason I do the outside of the hull last is so that I can prevent bleed through from the outside from blotching the finish ready interior. For all of the effort and time that goes into prepping the hull I want to make sure that it receives a perfectly applied layer of varnish to lock in the wood colors. I don't want it to get blotched up by boat soup. For the first layer of varnish inside the hull I blend Epifane and mineral spirits to about 25/75. I increase the amount of varnish with each subsequent application until I am applying 100% Epifane for the last 3 or 4 layers.

As Dan notes, there are differing opinions about the need for anything applied to the outside of the hull or what it should be. There are folks that apply nothing. Some apply thinned varnish. Some have their own blend of ingredients. Two things most of us agree about are that anything you apply on the outside of the does not penetrate very deeply and that using straight linseed oil directly from the can is not a good idea.
 
I am the oldschool guy and made just one.. i put hot boiled linseed oil with turpentine 3/1 in the inside, 3 days later followed by 4 layers of spar varnish evey second day mixed with thinner from 3/1 to 10/1 or so.

Then on the outside I put 1 layer of varnish, BLO and turpentine mix 1:1:1, wait 2 days and canvas on.

As some old hand who handled hundreds of canoes wrote here, he never experienced a problem with oiled hull but often saw too dry hull which had not been treated by anything.
 

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I've been reading through the various threads on this general subject and everyone seems to do things a little differently. When I first read Stelmok and Thurlow, it made sense to me to treat the interior and exterior with a mixture of boiled linseed oil and some kind of fungicide. I've made heavy use of a heat gun, so the remaining old wood is pretty dry. I'm also concerned about rot, especially between the old ribs and planks that remain. I've stained the inside, if that makes a difference. I thought I'd reopen the discussion, but at this point I'm inclined to go with jva74's instructions above:
"hot boiled linseed oil with turpentine 3/1 in the inside, 3 days later followed by 4 layers of spar varnish evey second day mixed with thinner from 3/1 to 10/1 or so.
Then on the outside I put 1 layer of varnish, BLO and turpentine mix 1:1:1, wait 2 days and canvas on."
 
I'd use caution using orange shellac as a base for marine varnish. I once used it to color correct ash rib caps. They looked fine, but when I started to hammer the caps in place the varnish developed blisters and delaminated - it just wouldn't stick properly to the shellac. So never again for me. I understand that you can get 'de-waxed' shellac but I believe it lacks waxed shellac's orange tint.
 
You can get many colors of dewaxed shellac, especially if you mix your own. I use it under marined varnish on most canoes. It helps to hide the new stained ribs and new wood. It is important to scuff it like you do between coats of varnish to give it some "tooth".
 
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