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Boiled Linseed Oil

wdrite's picture

Boiled Linseed Oil (post #111245)

What is the latest scoop on boiled linseed oil?  I know that in the past, boiled linseed oil contained metalic driers including lead.  I have heard that the practice has been discontinued.  I have a can in my shop that I have examined for information about this.  Not a word about it containing anything but llinseed oil that, through processing, dries 3 to 4 times faster than raw linseed oil.  Is boiled linseed oil food safe or does it contain additives making it unsafe?  If it has these driers, why aren't they listed on the container?

resenergy's picture

(post #111245, reply #1 of 13)

I don't have an answer to your question, but I find that walnut oil does exactly what I want it to for food contact surfaces. It rubs on easily, soaks in well, dries and polymerizes into a nice hard finish, and you can buy it at your local health food store.

I save the boiled linseed oil for my tool handles, canoe paddles and priming window sashes before reglazing.

wdrite's picture

(post #111245, reply #3 of 13)

I also use walnut oil on kitchenware but it is sometimes hard to find. I like that it does not yellow light colored woods as does linseed.  I would still like to know about boiled linseed.

Kevin's picture

(post #111245, reply #9 of 13)

As I mentioned in another comment, I've used Walnut oil on Maple. My experience was that it definitely yellowed the Maple very noticably. I've never used BLO, so I have no point of reference there.

Kevin's picture

(post #111245, reply #8 of 13)

How long did it take for the Walnut oil to dry? I've used some that I bought at WoodCrafters that's heat-treated and was very unhappy with how it never seemed to dry. The heat treating was supposedly to make it dry better, just as the "boiling" of linseed oil is supposed to make it dry faster.

The first time I used the Walnut oil I applied a coat & wiped off the excess, let it dry 24 hours and then applied another coat & wiped off the excess and let it dry another 24 hours, then I lacquered it. At first it seemed fine but within a few days I noticed that the lacquer seemed slightly gummy. I let it sit for several weeks and then sanded off the lacquer as best I could (it gummed up sandpaper REALLY badly!) and let it sit for over a month. When I figured it had finally dried I went to sand it again and had the same exact problem with it gumming up the sandpaper really badly. This was on Maple wood.

YesMaam27577's picture

(post #111245, reply #10 of 13)

1.  Walnut oil is not one of the oils that will polymerize in wood. Heating it won't help.(Linseed oil will polymerize.) Polymerization is the chemical process by which some oils blend with wood, dry and harden into a sort of plastic. Since walnut oil will not polymerize, it should not be used under any film-forming finish. But in pure form, it is food safe.

2. "Boiled" linseed oil has not been boiled - probably not even heated. It has had chemical driers added. This will substantially decrease the time needed for polymerization (a few days total cure time, versus a few weeks or more). Because of the chemical driers, boiled linseed oil should probably not be used for food-contact items. Although its difficult to find, linseed oil is available in food-grade -- sometimes its called Flaxseed oil.

The gummed up sandpaper happened because the lacquer was not cured -- with walnut oil under it, it can't cure, because the walnut oil never dires.

This is one of those cases where you need to clean the workpiece with lacquer thinner, then with mineral spirits. You need to get all of the lacquer and all of the walnut oil off of it (and out of the pores). Then let it sit for a week or more, to be sure that nothing seeps out.

Then start over.

But don't feel bad. I made this very same mistake when I was learning, as did (I'm sure) many of the others here at Knots. We all learn as we go.





Support our Troops. Bring them home. Now.  And pray that at least some of the buildings in the green zone have flat roofs, with a stairway.

. . I can't live proud enough to die when I'm gone, So I guess I'll have to do it while I'm here. (Phil Ochs)
resenergy's picture

(post #111245, reply #11 of 13)

I could have been mistaken when I said Walnut oil pollamarized. It definately does soak in and forms a nice finished surface. I would never use it under any other top coating such as a laquer. It is an oil finish in and of itself, useful for wooden food utensiles, bowls and cutting boards. Probably not hard enoughtfor furniture etc. Over time, these items may need reoiling, especially if washed in detergents, but that is an easy and pleasant task.

Kevin's picture

(post #111245, reply #12 of 13)

I've been told both that Walnut oil will dry and that it won't, and both from credible sources. So the jury is still out on the issue in my mind. The late, great Jon Arno (wood species expert extraordinaire for FWW magazine) once told me right here at Knots that Walnut oil will dry and it's hard for me to discount him because of his profound expertise. Of course anyone can be wrong, even an expert. But I'm still wavering. Nevertheless, my experience with it was highly disappointing.

If you dig into the history of BLO I think you'll find that "boiling" it was once the method of choice for altering it's chemistry so that it would dry faster. Now days chemical driers are used, as you pointed out. But the terminology has never changed and probably won't.

BTW, the oxidation or polymerization of oils is typically a literal curing by contact with oxygen rather than a blending with the wood.

SteveSchoene's picture

(post #111245, reply #13 of 13)

I think even the boiling was for the purpose of encorporating lead as the drying agent, not just a partial polymerization. 

On another point, I suspect that the main thing that keeps manufacturers from FDA approval labeling is that testing, of materials, the cure, and the leaching of certain chemicals would have to be done--on every batch of finish.  I doubt the quantity demanded for BLO with the labeling as FDA safe, at $75 a quart (or some such number) would be very attractive for most manufacturers. 

Even without testing for FDA labeling, manufacturers must FIRMLY believe the risk to consumers must be negligable.  The lawyers that require coffee cups to say contents are hot would surely be saying "no food contact" if there were any chance of being sued over the matter.  With lawyers working to bankrupt the coating companies over pre-1970's lead contact, the companies must have some awareness of the tort system. 

Test your finish on scrap, FIRST, or risk having to scrap your finish.

lwj2's picture

(post #111245, reply #2 of 13)

Tried & True Finishes uses a process that does not include metallic driers.

I've never used it, there have been a variety of comments on this and other boards both pro and con.


Leon Jester, Roanoke VA

SteveSchoene's picture

(post #111245, reply #4 of 13)

Boiled Linseed Oil does indeed contain metallic driers.  The driers aren't listed because they aren't considered hazardous.  It does not contain lead (though it used to--before the late 70's--because lead is a more effective drier.)  When the oil cures the driers are linked with the cured oil so the driers are not available to do any harm.  It is safe to use around food once it has cured--about a month, the same as with other oil based finishes. 

As far as I know, the Tried and True products are based on polymerized linseed oil--"partially reacted" that will cure, though some may take a very long time if not applied very, very thin.  They are safe also, but any difference in safety is going to be very very small indeed.   

Test your finish on scrap, FIRST, or risk having to scrap your finish.

nikkiwood's picture

(post #111245, reply #6 of 13)

Bob Flexner has been saying for years that the notion that only some oils are safe for food contact is a myth (to put it kindly) spread by Behlen to promote their Salad bowl finish.

As Steve says, the truth is any oil is safe once it has cured for 30 days.

"It is what we learn after we think we know it all, that counts."

John Wooden 1910-

*** "It is what we learn after we think we know it all, that counts." John Wooden ,1910-2010

YesMaam27577's picture

(post #111245, reply #7 of 13)

Perhaps what we're talking about here is the difference between "nontoxic" and "food-safe".

To the best of my knowldege, every clear finish that we might use on a woodworking project will be nontoxic once it is properly cured. This includes oils, varnishes, lacquers, shellac -- all of them. And if a toddler chews the edge of the table, no harm done.

And I guess that if you're not too picky, you could use any of those for food-contact projects in your own home -- hey, it's your liver.

But don't make them for sale unless you research how the FDA and the Health Department define "food-safe". You'll probably find that they require oil finishes to be from food-grade walnut oil, food-grade mineral oil, or food-grade linseed oil.

As for the varnishes, lacquers, and shellac, I haven't done the research -- perhaps there are specially-formulated finishes.






Support our Troops. Bring them home. Now.  And pray that at least some of the buildings in the green zone have flat roofs, with a stairway.

. . I can't live proud enough to die when I'm gone, So I guess I'll have to do it while I'm here. (Phil Ochs)