Linseed oil and Cuprinol


Curious about Wooden Canoes
Making progress on the OTCA. Got the tips redone. Now it's time to oil, varnish, and canvas - yikes!

In Stelmok's book he recommends boiled linseed oil with about 20% clear Cuprinol. Can anybody tell me where to buy clear Cuprinol (other than shipping from England)?

Or is there an alternative to clear Cuprinol that I should use?

In my goggle searching I have come across:

1 Cuprinol No. 10 Green Wood Preservative
2 DAP Woodlife Wood Preservative
3 Wolman Clear Wood Preservative

and I am leaning towards the Cuprinol Green but I really don't know.

Thanks for any help,

John H
Given the choice, I'd go with Deks Olje #1. I'm not a linseed oil fan as tests by the Forest Products Lab have shown that it makes great food for mold, mildew, etc. and I don't like oil finishes that often turn black....maybe black and green if you mix it with Cuprinol.

As an easy to use, effective, oil-type wood sealer for boats that won't stay sticky or turn black, Deks Olje#1 is the best I've ever used. It used to be available in the US, then wasn't for a while and is now available again. Room
Todd, thanks for the info.

What do you think about using Deks #1 for both sides of the hull, and then use Deks #2 for the inside (instead of marine varnish)?

John H
I've used Deks#1 as a base for varnish without a problem (give it a few days to dry thoroughly) and I think some builders like Freedom Boat Works were also using it that way. I never seemed to warm up to Deks #2 though. Maybe it was my application technique, but I seemed to get a nicer, smoother finish with real varnish. Note that I didn't spend a lot of time messing with Deks #2. I tried it, looked at the result and moved on, so I can't really say much about its durability, ease of re-coating, etc. There may be people who get great results with it, but I don't think it has as many supporters as Deks#1.
Generic "Cuprinol" is sold here (Canada) at most hardware stores as clear or green preservative; "protects wood, canvas, and rope against rot, mould, fungus, mildew, decay and woodboaring insects". Clear contains petroleum distillates and zinc naphthenate (the green version contains 2% Copper Naphthenate). Costs $9.99 a gallon (3.78 L)
Apart from other reasons, you may not want to use green cuprinol mixed with (orange) linseed oil because green and orange are very nearly complementary colors and will combine at best to a dark brown, but more likely a neutral gray. :(
I am currently dealing with the fun of sanding off the 'dark brown' residue from the previous fiber glass. This is a major pain in the arse, the 'dark brown' quickly gums up sand paper.... But, I am almost done.

I have found Deks Olje D1 locally and am going to try that. It's kind of pricey - $34 a liter!

Thanks for all the help.

John H
linseed oil

Raw linseed cut 30 % or less for the interior. No browning over time and becomes a very natural part of the cedar fibers as it will not be a highly polymerized (boiled) addition to the wood structure. BL is essentially a foreign material. More details if you need, John...on the application etc.
I have been using Deks Olje on the Ausable Riverboats that I build for 30 years.Have been very happy with Deks. Also very easy to refinish in most cases just wash good and light sand and recoat. You can get Deks Olje #1 from Hamilton Marine in Maine for $60.99 for a 2.5 liter can.
Generally; I use boiled linseed oil with turpentine and paint thinner in a ratio of about 1 part linseed oil to 4 or 5 parts turp/thinner. ( I don't measure it) on both the inside and outside of a w/c canoe. Actually, most of the stuff evaporates after I leave it outside for an afternoon. After it dries. in a day or two, I varnish the interior AND the exterior of the hull. The interior gets a lot more than the exterior, but I like to see some sheen on the exterior. Does it help? Who knows, but it might help decrease the moisture absorption of the cedar. Gil
Generally; I use boiled linseed oil with turpentine and paint thinner in a ratio of about 1 part linseed oil to 4 or 5 parts turp/thinner. Gil

I know that Rollin uses a similar concoction on his canoes and rebuilds.
I don't dabble with this nearly enough to offer an opinion about an alternative so I'm following yours and his lead. It seems silly to second guess a couple guys that have done so many hundreds of canoes.
That said, I'm sure that the other options also perform perfectly well.

As an aside, we have not been able to buy Cuprinol in NYS state for a real long time. It's been banished along with half of the paint products and wood treatments that we used to use.
The 80% linseed oil with 20% Clear Cuprinol formula was made up when the Clear Cuprinol was and oil base produce. Although the time tested method of using straight boiled linseed oil on the cedar hull was/is very effective, I thought that a bit of extra preservative mixed in with the linseed oil would be a good addition to soak into the cedar hull. The oil base Clear Cuprinol mixed well with the linseed oil and it seemed like a good idea to mix the two. A few years latter Cuprinol changed the clear formula so it was a water base product, and of course that does not mix well with the linseed oil at all.
The Wood and Canvas Canoe book has never been up for a rewrite and now that it is out of print the incorrect linseed oil/cuprinol formula will still be out there to confuse the readers.
For those that think a bit of added preservative is a good idea then they have to find a preservative that will mix with the oil base linseed oil and use their best judgment on what ratio to use.

What I tell people now is basically I have just reverted back to the old system of using straight boiled linseed oil on the outside wood hull and varnish on the inside of the hull. After restoring hundreds of old hulls I can't say that I have ever encounter a problem with the outside of a hull because it was treated with linseed oil but I have seen lots of problems on hulls that were not treated with oil and were dried out, stiff and not in very good condition. Using straight linseed oil or other kinds of oils on the inside of the hull with no coverage of a varnish never turns out well. The oil does keep the wood from drying out but it also tends to get dirty easily, turns black with age and does not prevent the wood for getting beat up. These are not problems on the outside of the hull because the hull is covered with the canvas.

Bare canvas and the linseed to make a nice breeding ground for mildew but the mildew will effect the canvas long before it effects the wood hull. Even without the oil, the unprotected bare canvas is subject to the mildew problem so the solution is to have some kind of mildew protection for the canvas. Oil for the wood; mildewcide for the canvas, and the boat will be very happy!
Because I usually do my canoe playing (work) in winter in the basement, turp doesn't work for me, much too smelly.

So my modification of the std is,

linseed oil/low odor mineral sprits about 50/50 with a 1 oz packet of mildewcide from the home ctr on the outside.

Tung oil in the same mix as above on the inside.

Varnish is required in the interior of the canoe; tung oil or linseed oil alone is not enough to provide adequate protection the the soft cedar.