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Forum topic by Treebane posted 12-15-2019 09:11 PM 852 views 0 times favorited 35 replies Add to Favorites Watch
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Treebane

9 posts in 259 days


12-15-2019 09:11 PM

Topic tags/keywords: linseed oil safety fire hazard

Hi all,
woodworking is a new hobby of mine and up to this point I haven’t really used any finishers. I’ve just sanded the pieces on the lathe.

I’ve been recommended linseed as a finisher, raw linseed not boiled. What’s the difference between these? From what I could gather raw linseed is food safe while boiled linseed is not. Additionally boiled linseed is cured after two-three days while raw linseed could take weeks or months?

Is this correct?

When it comes to safe handling of both types of linseed oils (or any oxidating oil), it is my understanding that the rags pose a fire hazard as the rags (or paper towels) are bad at dissipating heat. I’ve only used paper up until this point due to how cheap it is to dispose of compared to rags.

But what about firehazard of the treated wood? Is this a thing? Could I risk that small pieces (or big pieces for that matter) of wood I’ve turned on the lathe pose a fire hazard as well?

What about spilled drops of oil on the workbench or saw dust on the workbench? I’ve become paranoid and is really uncomfortable with linseed oil. I toss the oil soaked paper in a metal container after I’ve used them, and usually burn them in our fireplace afterwards. It’s actually at the point where I’m scared of putting the metal can containing the linseed oil back on the shelf as there will always be a little bit of oil on my hands afterwards.

Any tips and input on this matter is highly appreciated.

Kind regards,
Treebane


35 replies so far

View Bill White's profile

Bill White

5242 posts in 4566 days


#1 posted 12-15-2019 09:33 PM

Raw linseed oil has no dryers added. Boiled LO does.
No probs with either on your hands.
Fired hazard occurs when rags, etc. are confined as in wadded rags or paper. Laid out flat, the rags/paper will dry as expected.
I’d say that amounts in sawdust confined would be a hazard, but the small amounts on the bench top would not.
Just be careful with ANY finish, and you will be OK.
Just sayin’ what I do.

-- [email protected]

View bondogaposis's profile

bondogaposis

5605 posts in 2957 days


#2 posted 12-15-2019 10:55 PM

If you spread your used rags out and let them dry they won’t generate enough heat to combust. I spread mine around the edge of a trash can. I would not put a bunch of oily rags in a tin. When they are dry they are no longer a hazard. I wouldn’t use raw linseed oil as a finish because it takes too long to cure. Boiled linseed oil is a misnomer because it is not boiled, they just add driers to it so it will cure in a reasonable amount of time. Those driers have metals in them and they are not food safe. You can get polymerized linseed oil, which is linseed oil that has been heated and it will cure without driers. Tried and True sells a couple different options with polymerized linseed oil. You can also get “stand oil” at art supply stores, it is linseed oil that has been heated as well.

-- Bondo Gaposis

View Kelly's profile

Kelly

2630 posts in 3550 days


#3 posted 12-16-2019 12:04 AM

Ditto spreading the rags out. Been my habit for years. You can do it with diapers and it makes and interesting wrinkled canvas.

Once on the project, zero problem, BUT you MUST wipe off the excess to avoid ugly wrinkles. On that, back to the rag thing….

Myself, I’d never used flax seed oil (raw linseed oil) for a finish, unless life as we know it ended. Even then, I’d try to add pine tar, pitch or what have you.

I keep BLO around by the gallon, like most do, and do not depend on it by itself for a finish. Like thousands of others, I add other stuff to make a more durable friction polish. Easy formulas all over the Net for making your own, and for using them.

Unlike the raw flax seed, friction polishes can be ready for use in minutes, using them with a lathe.

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

705 posts in 153 days


#4 posted 12-16-2019 01:00 AM

Cold-pressed raw flaxseed oil has been used for centuries in scandinavia as a wood treatment, and still is. The clearer the oil, the higher the quality. The more orangey the color, the more inferior the quality. They feed it to horses and cows as a supplement as well. The best quality paint I have ever used was simply linseed oil and added pigments.

It is true that it takes the raw type a long time to cure, like months. And It penetrates deep into wood, like no petroleum product can do. Like Kelley said, a very good wood preservative in pinetar cut with linseed oil. There are wooden church roofs in sweden that have been preserved for 1000 years with just pinetar and linseed oil.

The original, organic way of “boiling” oil just meant that it was purified with oxygen, which removes protein and speeds drying time and increases shine, and also made it mold and mildew free.

You never want to go over linseed oil with laquer because you will have a sticky gummy mess to deal with. Shellac will bind to anything, and lays over linseed oil nicely.

-- Wildwood by Brian Johns: If you tell the truth, you dont have to remember anything (S. Clemens) Edit: Now where is that darn pencil/ tape measure!

View Kelly's profile

Kelly

2630 posts in 3550 days


#5 posted 12-16-2019 02:13 AM

Keep in mind, merely that people did something a certain way back when does not mean it’s the best way to do it today. HOWEVER, sometimes, old technology is still the best way.

Look at shake roofs. Since experts got involved, they no longer last a hundred years. The solid sheathing required under shakes in this day and age does not allow them to dry.

Then there is the exterior finish thing. Poly is a horrible exterior finish for decks and wood fences, but you wouldn’t think so to listen to companies pushing their product. Non-hardening oil, applied aggressively, until the wood won’t take any more will stop cracking and splitting.

Where a hardening oil is appropriate, adding resins and such can turn them into pretty good finishes.

View Treebane's profile

Treebane

9 posts in 259 days


#6 posted 12-18-2019 07:56 PM

Thanks for all your replies, I really appreciate it. It put some concerns to rest.

How come there’s no danger with combustion of treated wood? Is wood sufficient at transferring heat? Is this also why the oil should be stored in glass or metal containers?

What about burning oil soaked paper in the fireplace, is this a bad practice?

Thank you all once again.

View jdh122's profile

jdh122

1120 posts in 3423 days


#7 posted 12-18-2019 08:20 PM

My 2 cents: I’ve pretty much stopped using linseed oil and instead moved to all tung oil, which can provide a nicer luster, a bit less yellow, and a bit more protection. As for using linseed oil, most “boiled” linseed oil is not boiled at all, but rather treated with the addition of chemical dryers (raw linseed oil will cure, but very slowly, the dryers speed it up). If you’re worried about the non-food safety of the dryers (they probably all evaporate off) you can use a real heat-treated linseed oil with no additives, like the one sold by Tried and True finishes. It’s very nice to use and a little goes a long way. But in my experience it gives a finish that is much more matte than I can get with tung oil.

Drying oils (there are no doubt others, but tung, linseed and walnut oils are the ones I see reference to), all produce heat as they cure. When they’re spread out in a thin layer on wood (and they have to be spread very thin – think all excess wiped off, and often even re-wiped off 20 minutes later) it’s nowhere near enough heat to be dangerous. On a single layer of rag it’s also not a problem, which is why spread out rags don’t combust. Oil-soaked, wadded up rags, on the other hand, intensify the reaction, provide less escape for the heat and are made of inflammable materials. I have good friends who almost lost their house from a fire that started that way (firemen got the fire out).

-- Jeremy, in the Acadian forests

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Kelly

2630 posts in 3550 days


#8 posted 12-19-2019 04:41 AM

jdh122, just for future reference, all linseed oil is not boiled, as in a boiling cooking process. It’s said the boiling name came from the visible effect of air being passed through it in the polymerization process.

Tung and linseed oil are better described as hardening oils than drying oils. They harden in reaction with oxygen.

I agree on the tung oil thing. I was fortunate to be able to buy from a place just a couple hours away, Winthrop, Washington. They sold top cabin stuff by the gallon, along with the hardeners. Sadly, they went out of business.

View SMP's profile

SMP

1588 posts in 511 days


#9 posted 12-19-2019 06:45 AM



Thanks for all your replies, I really appreciate it. It put some concerns to rest.

How come there s no danger with combustion of treated wood? Is wood sufficient at transferring heat? Is this also why the oil should be stored in glass or metal containers?

What about burning oil soaked paper in the fireplace, is this a bad practice?

Thank you all once again.

- Treebane

Its more of a conservation of energy thing. As the linseed oil (or other drying oils like tung oil) polymerizes, heat is released as part of the reaction. Not a lot of heat, but when the medium is crumpled in a ball that heat is multiplied, think of like a piece of coal turning into a diamond. This gives the chance of combustion under the right conditions. Once it is dry, it is now inert.

Fwiw, as I am trying to move away from chemicals and VOCs i just make my own actual BLO. I just get raw linseed or flax oil and boil it. I keep some plain and some I mix in 50:50 with pure food grade beeswax. This gives a nice natural finish that is easy to repair/maintain.

View Fred Hargis's profile

Fred Hargis

5927 posts in 3099 days


#10 posted 12-19-2019 11:20 AM


Fwiw, as I am trying to move away from chemicals and VOCs i just make my own actual BLO. I just get raw linseed or flax oil and boil it. I keep some plain and some I mix in 50:50 with pure food grade beeswax. This gives a nice natural finish that is easy to repair/maintain.

- SMP

Isn’t that a little dangerous? How do you boil it? Just curious.

-- Our village hasn't lost it's idiot, he was elected to congress.

View jamsomito's profile

jamsomito

457 posts in 1032 days


#11 posted 12-19-2019 12:12 PM


Fwiw, as I am trying to move away from chemicals and VOCs i just make my own actual BLO. I just get raw linseed or flax oil and boil it. I keep some plain and some I mix in 50:50 with pure food grade beeswax. This gives a nice natural finish that is easy to repair/maintain.

- SMP

Isn t that a little dangerous? How do you boil it? Just curious.

- Fred Hargis

This is a good instructional: https://youtu.be/VtETzSg4LcE

View SMP's profile

SMP

1588 posts in 511 days


#12 posted 12-19-2019 01:09 PM


Isn t that a little dangerous? How do you boil it? Just curious.

- Fred Hargis

This is a good instructional: https://youtu.be/VtETzSg4LcE

- jamsomito

Yeah thats the video that got me to try it. I use my bbq outside so my wife can’t yell at me for starting a fire, even though she makes french fries inside, which is essentially the same thing. I would say its a little less dangerous than frying a turkey since you attend to it all time with a candy thermometer. I think the danger with turkey fryers is people leave it unattended since it takes so long.

View OSU55's profile

OSU55

2503 posts in 2595 days


#13 posted 12-19-2019 02:03 PM

Ive been finishing wood for 30+ yrs and turning for ~ 7 yrs. I never use blo or raw, neither have a use for interior applications IMO. There are superior products and methods available. I recommend the book Understanding Wood Finishes by Bob Flexner. As a primer this may be helpful.

View Kelly's profile

Kelly

2630 posts in 3550 days


#14 posted 12-19-2019 04:15 PM

OSU55, I agree, 100%, on the issue of using raw flax seed (linseed) or tung oil. You gain nothing by using them raw, except more work and wait time.

Of course, any of us who use things like high end polymerized finishes, like long oil finishes common to the marine environment, we do use linseed oil.

The tung oil I favored was like the boiled linseed oil, it was already partially polymerized by the company selling it. That that, you could add hardeners the company sold to speed the hardening process to something reasonable.

The ONLY thing I use straight hardening oils for is to bring out grain. Once there, I switch to the “resin added” versions, be it a wipe on, or a brush or spray on version.

For the lathe, I add a few things, like denatured alcohol, shellac and linseed oil, to keep that instant gratification thing going for items that will not see hard use, like certain bowls or mugs.

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

705 posts in 153 days


#15 posted 12-19-2019 05:11 PM


Fwiw, as I am trying to move away from chemicals and VOCs i just make my own actual BLO. I just get raw linseed or flax oil and boil it. I keep some plain and some I mix in 50:50 with pure food grade beeswax. This gives a nice natural finish that is easy to repair/maintain.

- SMP

Pretty much where I am at. I do love me some shellac. Lately I have been using spray-laq on builds that are too much of a PITA to build a shellac finish on.

-- Wildwood by Brian Johns: If you tell the truth, you dont have to remember anything (S. Clemens) Edit: Now where is that darn pencil/ tape measure!

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