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Thread: Raw linseed oil and blackening

  1. #1
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    Default Raw linseed oil and blackening

    I'm building a small lapstrake pram. Since I'm spending an arm and a leg for the wood I want to make sure it will last a long time. I also like the wood's natural look. My question is what causes the linseed oil to turn black over time? I've heard that it's because mildew will grow and feed off the oil and also that it's the oxidation of the oil over time. I would like to saturate the wood with heated raw linseed oil and after it has dried for three to four weeks finish with Le Torkinoit varnish. Since Le Tork has a raw linseed oil base its adhering is not a problem. I am curious if this would prevent the wood from turning black by blocking the oxidation or keep it from mildewing? The other option would be to saturate the wood with raw tung oil. I want to varnish the inside and paint the outside of the hull.
    Does anyone out there have any experience with this or thoughts on the matter? I'm using spruce for the planks, Douglas fir for the transoms and seats and oak for the frames. One other thought. Does anyone know of a source for natural knees?
    Last edited by B.Duncan; 09-29-2009 at 07:34 PM. Reason: I mentioned spruce for the frames. The planks will be spruce.

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    Default Re: Raw linseed oil and blackening

    My experience with La Tonkinois over raw linseed oil is very good. The linseed oil was cleaned oil from Allback, but the look is very bright and clean after two years on both a mast (sitka) and dinghy seats (butternut). Tung oil is a drying oil and will not penetrate like raw linseed. The linseed you can apply day after day, it will continue to absorb and not build up. No need for thinners.

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    Default Re: Raw linseed oil and blackening

    If you don't like black wood, go for Le Tonk or another oil-based varnish. My understanding is that the UV turns raw linseed oil black over time, and that mold isn't as much of a problem for boats in cold climates.

    You can use non-boiled linseed oil but may have to wait a looooooonng time before you can varnish with anything. The urge to get the boat in the water may be hard to resist at that stage of the build...
    Last edited by Thorne; 09-28-2009 at 10:47 AM.
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    Default Re: Raw linseed oil and blackening

    Unlike the common notion, varnishing and painting over raw linseed oil works well. You do want to let it soak in for a day at least and the first coat may be slow to dry, but you can recoat in the normal time frame (next day) and that coat and subsequent coats will be fine.

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    Default Re: Raw linseed oil and blackening

    From Wikipedia, the free encyclopedia

    A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air. The term "drying" is actually a misnomer - the oil does not harden through the evaporation of water or other solvents, but through a chemical reaction in which the components crosslink by the action of oxygen. Drying oils are a key component of oil paint and some varnishes. Some commonly used drying oils include linseed oil, tung oil, poppy seed oil, perilla oil, and walnut oil.

    I know of no reason why tung oil would not penetrate as well as linseed oil; it does not turn black; it is quite a bit more expensive, which is the primary reason linseed oil is used instead. Tung oil is often "raw," but is also often treated to make it "dry" -- that is, chemically cure -- faster, just as linseed oil may be boiled (chemically treated) to make it cure faster.

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    Default Re: Raw linseed oil and blackening

    tung oil is a drying oil, it does not have to be treated to "dry", by the second coat tung will start to film on the surface. linseed oil raw can be applied daily for weeks on most woods and will be absorbed. if you buy "boiled linseed oil" you are buying chemically treated oil that will "dry". if you heat raw linseed oil (boiling, but not to be done in an open pan because it will "flash", best done "double boiling" in a water bath) it will become a drying oil, "curing faster" as they say -- that is why the chemically treated oil is called "boiled", as it was for many many years. the old way still works.

  7. #7
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    Default Re: Raw linseed oil and blackening

    I have painted over linseed oil without problems. But its 20+ years ago and I cant really remember to well. So you say that you can paint when its not fully cured
    Another thing: Is it a bad idea to treat the inside of a glued plywood (lapstrake) boat with linseed oil? I actually like the blackening effect.

    Quote Originally Posted by Thad View Post
    Unlike the common notion, varnishing and painting over raw linseed oil works well. You do want to let it soak in for a day at least and the first coat may be slow to dry, but you can recoat in the normal time frame (next day) and that coat and subsequent coats will be fine.

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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by Thad View Post
    Unlike the common notion, varnishing and painting over raw linseed oil works well. You do want to let it soak in for a day at least and the first coat may be slow to dry, but you can recoat in the normal time frame (next day) and that coat and subsequent coats will be fine.
    I concur, at least for paint. I have no experience with varnish over raw linseed.

    I've found that two days between oil and first coat of (oil-based) paint works well. BTW, after a first coat of oil-based paint over linseed, you can do subsequent coats in latex, if you choose.

    I have no idea whether linseed oil treatment will act as a preservative. It's presence will of course help displace other liquids that would otherwise be absorbed. It will prevent fir plywood from checking.

    As Thad says, you must use raw linseed oil, not boiled.

    Wayne

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    Default Re: Raw linseed oil and blackening

    I use teak oil to protect the interior of my cedar planked lapstrake peapod. (Just the planking ... not the brightwork. I use a fairly traditional varnish for the thwarts, knees, centerboard case, breasthooks and rails).

    To apply the teak oil ... I spray it on with a plant mister, let it settle a little, rub it in with a scotchbrite pad, then wipe it out with rags. Don't let the teak oil pool or congeal. Teak oil will give your planking a nice warm finish that you'll have to refresh when necessary. It'll darken a bit over time, but won't turn black like linseed oil.

    If you get a product with UV added, that's even better. I use Daly's, but have used other cheaper brands, too. Not sure the actual brand really matters.



    Just for the record ... this is the method that Eric Hvalsoe uses in his cedar boats, and he's the guy who I got this method from ... though the plant mister idea was mine.



    Just curious, but where did you buy your materials? Specifically, where did you get your cedar and your bending oak?
    Last edited by Yeadon; 09-28-2009 at 02:45 PM.

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    Default Re: Raw linseed oil and blackening

    I've been using Teak Oil, specifically from Dalys here in Seattle, for decades. Someone here on the forum recently pointed out that it is a tongue oil base. I am inclined to agree that tongue oil is less likely to darken, or will darken at a slower rate than linseed oil. I don't know the chemistry. Red Cedar will absorb at least a couple of coats of Teak Oil. I refresh once a season, maybe more depending on use. As tim said, I do not build up a heavy film, the spray bottle is a great idea. It is nice to enjoy the wood for a few years, rather than a heavy linseed oil base 'boat sauce'. Of course it is true that linseed oil has been central to coating and preserving boats for centuries. Modern 'teak oil' seems to be a very straightforward application. Dalys will add a UV component.

    Varnish over a linseed oil sealed interior does not seem like a bad idea - except - why do you want to varnish the interior of a traditional lapstrake hull? I say that simply because I have stripped the interior of a varnished lapstrake hull gone bad - and would not wish that on my worst enemy. An open glued lap hull with no ribs - seems a much better argument for paint or varnish.
    I occasionally seal parts with linseed oil and turps.

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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by Wayne Jeffers View Post
    I have no idea whether linseed oil treatment will act as a preservative. It's presence will of course help displace other liquids that would otherwise be absorbed. It will prevent fir plywood from checking.
    If it does not have any preserving properties, why would one use it then? Re-hydration of wood can be done simply with water.
    There is a thread on the forum where Bob Smalser says linseed oil is good for filling poors prior to varnishing on wood with a rather open structure.
    I read that in the old days they used linseed oil as a preservative for wood, but I have no idea how effective it is. Does anyone have more knowledge about this?
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    Default Re: Raw linseed oil and blackening

    I use raw linseed for my umiaks frame. I'm rather fond of the blackening though.

    Poulsbo boat is filled with varnish. Not looking forward to that so much.

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    Default Re: Raw linseed oil and blackening

    You used to be able to buy knees from the late norman Gee up in maine. If you call his widow, maybe you can buy some of his old stock.

    -Thad
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    Default Re: Raw linseed oil and blackening

    We are told that raw linseed oil applied directly to wood will always boil up under paint or varnish eventually. Has some connection to it never actually really drying completely. I've had some really bad experiences with raw linseed oil.

    We use boiled linseed - either directly on wood or mixed with turpentine. Then varnish or use a top-coat oil like owatrol or benar.

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    Talking Re: Raw linseed oil and blackening

    Thanks all for your insights. I now have a goodly amount of information to digest.

    To Yeadon... I'm getting my wood from McClanahan Lumber in Forks, WA. I'm using spruce instead of cedar and the oak ribs will be sawn instead of bent. I would love to find a small specialty saw mill in Washington or Oregon that mills oak. So far no luck but I haven't begun searching all that hard also.

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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by Thad View Post
    tung oil is a drying oil, it does not have to be treated to "dry", by the second coat tung will start to film on the surface. linseed oil raw can be applied daily for weeks on most woods and will be absorbed. if you buy "boiled linseed oil" you are buying chemically treated oil that will "dry". if you heat raw linseed oil (boiling, but not to be done in an open pan because it will "flash", best done "double boiling" in a water bath) it will become a drying oil, "curing faster" as they say -- that is why the chemically treated oil is called "boiled", as it was for many many years. the old way still works.
    Boiled linseed oil is exactly as the description suggests, boiled. To oxidize the oil faster, simply add a dryer.

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    Default Re: Raw linseed oil and blackening

    In the states boiled linseed oil is not actually boiled, but has dryers added.

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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by cookie View Post
    If it does not have any preserving properties, why would one use it then? Re-hydration of wood can be done simply with water. . . .

    . . . I read that in the old days they used linseed oil as a preservative for wood, . . . .
    I’m sorry to be unclear in my previous post.

    When I said I had no idea whether linseed oil treatment will act as a preservative, I was thinking in terms of toxicity to the bacteria which cause rot.

    By helping displace other liquids (i.e., water) that would otherwise be absorbed, it will of course be of assistance in preventing rot. Even better would be keeping the boat indoors where it never gets wet at all. I would not characterize either as “preservative.” “Protective,” yes.

    I consider paint to be a “protective” coating, although many paints have a toxin added to inhibit the growth of mold which would discolor the finish over time.

    Linseed oil is the main ingredient in the traditional “boat soup” coating. I suspect boat soup is a preservative, rather than simply a protective coating. I suspect that anti-bacterial qualities come mainly from the pine tar, but the linseed oil may also have some anti-bacterial preservative properties.

    Wayne

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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by lagspiller View Post
    We are told that raw linseed oil applied directly to wood will always boil up under paint or varnish eventually. Has some connection to it never actually really drying completely. I've had some really bad experiences with raw linseed oil.

    We use boiled linseed - either directly on wood or mixed with turpentine. Then varnish or use a top-coat oil like owatrol or benar.
    I’ve never had a problem with paint adhering to wood I’ve treated with raw linseed oil. Please elaborate on your bad experiences.

    When pre-treating with raw linseed oil, I give the wood as much oil as it will absorb, then thoroughly wipe off the excess. I then wait about 48 hours before applying the first coat of oil paint. I’ve never had a problem.

    Coatings other than oil paint may or may not reliably adhere to raw linseed oil treated wood. Epoxy, for example, will not.

    To get the full stabilizing effect of linseed oil, you need to use raw oil. Raw oil soaks into the wood and, as you say, probably never really dries completely. Boiled oil stays on the surface and dries, though it is not a particularly hard coating.

    Remember: Raw oil soaks in. Boiled oil forms a skin.

    Wayne

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    Default Re: Raw linseed oil and blackening

    Supposedly the "ultra cleaned" linseed oil from Allback doesn't blacken as the proteins are all stripped out of it.


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    Default Re: Raw linseed oil and blackening

    The current Fine Woodworking has an excellent article on wipe on finishes in general .I wonder if Tung oil or the cleaned linseed oil would make the best oil and varnish wipe on ?
    Last edited by Bill Perkins; 09-30-2009 at 10:53 PM.
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    Default Re: Raw linseed oil and blackening

    I don't have much to add to the conversation except that everytime someone writes "tongue oil" I want to scream. It's Tung Oil

    Doug

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    Default Re: Raw linseed oil and blackening

    Oh yeah.I'll change that.
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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by Michael Beckman View Post
    In the states boiled linseed oil is not actually boiled, but has dryers added.

    Marketing.
    Boiling linseed oil adds viscosity to it. Boild linseed is made from the left overs.It starts as the steam separated portion , after the cold pressed has been extracted. It is treated with sulfuric acid to drop the contaminants, then it is boiled in the open air. Dryers are added for what ever purpose it is intended.

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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by S B View Post
    Boiling linseed oil adds viscosity to it. Boild linseed is made from the left overs.It starts as the steam separated portion , after the cold pressed has been extracted. It is treated with sulfuric acid to drop the contaminants, then it is boiled in the open air. Dryers are added for what ever purpose it is intended.
    Well if they just started calling raw linseed oil, "extra virgin linseed oil", it would all be much clearer (to those of us that watch the cooking channel).
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    Default Re: Raw linseed oil and blackening

    My bad experience was after painting wood I had first treated with raw linseed oil. The paint never really dried and took months to get past 'tacky'.

    I have also been told that raw linseed with alway boil up under paint eventually - but that is talking in terms of years.

    I might use a dash of raw oil in paint. But I have nothing but good experience with the boiled oil. It penetrates well, dries well and makes a good base for paint or varnish. Especially in a mix with American turpentine (real pine turp? Not the destilled stuff). That's my take on it.

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    Default Re: Raw linseed oil and blackening

    Quote Originally Posted by Thad Van Gilder View Post
    You used to be able to buy knees from the late norman Gee up in maine. If you call his widow, maybe you can buy some of his old stock.

    -Thad
    The late "Newman Gee"...of "Newman's Knees" he died logging wood for knees, grown crooks and root knees etc. According to many he was the best of the best. Kneews are no longer available from Newman's. Website shut down too.
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    Default Re: Raw linseed oil and blackening

    I seem to recall reading Pete Culler's articles once, and that he said that Raw Linseed Oil had better long term penetrating qualities, especially in planking. he recommended using it as the total treatment and finish. He said that Boiled Linseed Oil cured before it penetrated fully. So that would be great under paint or varnish, as a filler etc. But Pete said the raw oil was fine under paint too, you just had to wait longer afterwards prior to painting. He mentioned applying the oil hot. Personally I like Boiled Linseeed Oil as this is the bulk of my experience. I did use raw oil on a few toolboxes and it took a very long time to dry.

    If one were to heat Linseed Oil I would recommend using a double pan boiler, on an electric hotplate- no open flames or sparks in hot oil vapors!!!
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