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Mildewcide in oil finishes?

Discussion in 'Miscellaneous' started by pklonowski, Jun 27, 2015.

  1. pklonowski

    pklonowski Unrepentant Canoeist

    I'm doing some repairs on a wood-trimmed composite canoe, and finding once again that the oil finish was applied by the original builder only after final assembly. Of course, the rot started in all the unseen places, but it hasn't gotten out of hand just yet. The canoe is only two years old, though.

    I'm thinking about oiling all surfaces, to get that tiny bit of actual absorption into the wood, then several coats of spar urethane, to provide better overall protection, since the owner isn't going to do any maintenance himself. Is there a mildewcide I can add to the oil, so it gets into the base layers?
  2. Andy Hutyera

    Andy Hutyera The Red Canoe Guy


    Can't help you with something to add to the oil. I picked up some mildewcide in Canada at Andre's suggestion. I used it on untreated No. 12 canvas. It is sold by the gallon and is a clear foul smelling liquid. It penetrates very well and the smell goes away after a while. Why not do a two step process and apply the oil after the midewcide? The mildewcide is not available in the US but you could likely get one of our Canadiam friends to bring you some. I believe it is zinc based and is available at most hardware stores.
  3. Dan Miller

    Dan Miller cranky canoeist Staff Member

    You can get little packets of mildewcide from the paint shop or hardware. As I recall, a packet treats a gallon of finish, and is compatible with oil- or water-based finishes.
  4. Rob Stevens

    Rob Stevens Wooden Canoes are in the Blood

    Zinc naphthanate, sold as clear wood preservative eg;

    It used to be sold in plastic jugs, now in standard paint cans.
  5. Andre Cloutier

    Andre Cloutier Firestarter. Wicked Firestarter.

    Andy, how is the mermaid coming? any pictures?
  6. OP

    pklonowski Unrepentant Canoeist

    Many thanks.

    I picked up a product locally called "M-1", which is supposed to be for any interior or exterior, oil, latex, solvent, or water-based paint, coatings, and adhesives. The active ingredient is 3-iodo-2propynl butyl carbamate, which is a mouthful. Plenty of safety precautions, so it must do something. We'll see what happens!
  7. Andy Hutyera

    Andy Hutyera The Red Canoe Guy

    Andre, it's almost done but won't be ready for the Assembly. I'll post a couple of photos shortly. Still needs contrasting bottom paint, outwales and stem bands. Can't wait to get it in the water! Off to canoe camp this week trying to teach some young paddlers the J sroke.
  8. Todd Bradshaw

    Todd Bradshaw Sailmaker

    The best "mildewcide" for oil finishes is most likely more oil. Mildew gets down into the finish and the wood because water is getting down into them. You don't just put a couple coats of oil on and consider the project done for the duration. It is a continuing process of maintaining the oil and gradually building it up, down in the pores of the wood. As a former Mad River dealer, I can tell you that it is possible to continue to build their Watco oil finish until it's pretty much impervious to moisture or anything else. I can also tell you that when the boat comes out of the factory, it isn't anywhere close to that. When we would complain to Mad River about the rough and rather raw looking gunwales which were putting customers off, their reply was always "we don't have time to put more than a couple coats on before the boats ship out". If you do the typical light sanding or Scotchbrite pad followed by a fresh coat of oil and do it every month or two you'll start to build up a pretty nice finish in a year or two. Until you get to that point, it's vulnerable to moisture and what comes with it. I have yet to see an oil finish, no matter how old or well done, that I would really feel comfortable storing outside, but frequent refresher coats of oil is the best protection you can give it.
  9. OP

    pklonowski Unrepentant Canoeist

    I think the oil needs to be re-coated every couple of weeks, actually. That's pretty much why I go with varnish any more... It's harder to get a flawless finish, but I can deal with a few flaws better than I can deal with having to do that much work! There's too much else to do...
  10. Todd Bradshaw

    Todd Bradshaw Sailmaker

    About the only oil I use on boating stuff is Deks Olje #1. You apply multiple coats with a brush, wet on wet until the surface won't soak up any more and then wipe off the excess after the last coat. It may take five or six coats, but the application is very fast and easy and doesn't need to be fussed over. In a day or two it's dry and a gorgeous oil finish. Occasional refresher coats are again just brush, wipe and let it dry. It will be fine while you are actually using the boat, but you really don't want to store it out in the weather.

    I refuse to use linseed oil on anything. As far as I'm concerned, BLO sucks, as it were. Slow drying, often eventually turning black, and the fact that the Forest Product Lab's tests showed it to be really good food for the organisms that create rotten wood are enough reason that I won't use it.

    I've used Watco on boats, but believe Deks #1 is much better and easier to do on big pieces of wood. I do use Watco on gunstocks though. I sand up to 320 grit, wipe on a thin coat and let it penetrate for about 30 minutes. This initial coat is mostly to check and make sure that the surface is clean of any contamination and taking the oil evenly. Then I brush on a very heavy coat and let it sit for about 45 minutes - at which point, it will be very gummy. Finally, I take a piece of sturdy cloth like flannel and start wiping it off. This is quite a battle at first, but you keep at it until it is no longer sticky. This may mean 20 minutes of rubbing on a walnut butt stock before it's done. Once finished, it's a gorgeous satin oiled surface and smooth as a baby's bottom (though never having kids, I can't say I have ever actually touched a baby's bottom and don't plan to at any point in the future).

    As boats go, a canoe is small enough that if you really wanted to, you could probably do that sort of Watco treatment to the hardwood trim. I'm not sure whether or not it would work on cedar and spruce, where Deks #1 would certainly work great. Again though, I wouldn't store oiled finishes outside. These are all Watco refinishing jobs, and they were all disassembled, stripped of the factory varnish, oil refinished and reassembled in 24 hours or less using the flooded Watco technique.

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