boiled linseed oil BLO

Happens had a rag I was using start to smolder after the sun moved and so did the shadow. It was ouside oiling a pinic table that was drying out.

Both. Boiled linseed oil soaks in, then oxidizes and polymerizes (gums up). The oxidation can be a cause of spontaneous combustion if you leave a pile of rags saturated with the oil, because the "boiled" variety has catalysts that make it oxidize readily.

The finish, AFTER a cure period, is stable - and easy to renew- and lasts nearly forever. The liquid, kept sealed away from air, is stable, too.

Electric Comet wrote in news:mqm1h5$sv2$ snipped-for-privacy@dont-email.me:

This is generally true of any oil finish (linseed, tung, etc). As the finish dries, it polymerizes (the oil molecules link together), which is an exothermic reaction (generates heat).

If the finish is spread out (i.e. is on a surface you're coating) that's no problem, because the heat dissipates. If it's not spread out (e.g. is soaked into a wadded up rag) the heat is trapped, and can increase to the point of igniting.

For safety, you should spread your used rags (or anything else coated with oil) out somewhere with good air flow, and allow them to dry completely before throwing them in the trash.

Once dried, oil finishes are safe and stable.

John

Any oil based product is going to have a propensity to spontaneous combustion. But that is only until the product cures. The biggest risk is not being careful with the used rags and or brushes. Don't toss them in a trash can. I lay mine spread out on the concrete floor until they are dried, and then I throw them away, "on trash pick up day".

That's a great way to handle it. Spontaneous combustion of rags with oil b ased finishing materials on them is very well documented and you treatment is pretty much the "by the book" remedy to prevent a fire.

Personally, I have never seen it happen, but I actually knew a finisher tha t said his rags started to smolder inside a trash can he was using to toss all his dirty rags in while at work. It took two days, but he said there w as no doubt in his mind it was ready to flash.

Robert

Except that it will darken over time. But we're talking years - might even need refinished before the BLO gets really dark.

I'm convinced it legit, though I've never experienced it. I use to use BLO often and would take care to either burn the rags, myself, or seal them in paint cans, before tossing in the trash can. I don't "trust" any oily rags.

Sonny

Larry Blanchard wrote in news:mqo3sp$n2v$1 @speranza.aioe.org:

Also noteing that many woods will darken all of their own accord over time, regardless of what finish you put on them.

John

Ditto epoxy or polyester resins (in thick layers). It will get REALLY hot, makes BLO look like a piker. Especially polyester as it cures much faster.

The oily rags thing got pounded into me in my jr high shop classes. Growing up, I knew of several fires caused by oily rags. It still happens from time to time on the local news. There was a fire in town here last year from somebody refinish their floors. The floors were fine. It was the rags piled up in the corner that caused the fire.

I used to have a metal can to put the oily rags in. But they still got hot. So I started to put them out to dry. But rainy weather often interfered with that. If I have a sunny day, I will put out he rag to dry. Otherwise, I just burn the rag. A little newspaper and it burns right up. I supervise it till it is all gone. And I do it on concrete.

Some people just don't get this simple fact. I have had them pick up my drying rags and throw them in the trash. If there are any folks around I don't trust or know, I burn the rags. So folks think I am some kinda pyromaniac. Just the opposite. I want to PREVENT fires. Not cause them.

fighting fire with fire

but be honest we like the fire it is more primordial than buying new tools

yes it seems BLO has been used for a long time there's a recipe for leather preservative that uses BLO and animal fat and beeswax

i always just toss the rags or paper towels

was concerned with the finished product but it seems to stabilize

this makes sense and since BLO has been in use for so long if the finished product was a hazard no one would use it anymore

Same here, I leanred that in 7th grade. I never questioned it since I didn 't know ay better, but I seemed to have forgotten it along the way. Then I didn't do any finishing for years.

And yessiree, we have fires every year behind nearly finsihed construction projects from oily rags being incorrectly disposed of. Fires in dumpsters, fires in trash piles, you name it.

When I am on a job that generates a lot of dirty rags full of solvents and oils, I try to dry them out before I dispose of them. If I can't, I picked up a tip from an older fella many years ago. He told me that in HIS day, they had sealed metal cans that they put the rags in and dumped them out at the shop to dry. He said the proper procedure was to put about 3 inches o f water in the can (about 5 gallon size) and dump the rags in and put the l id on. I have used his method since then, and have had no problems. I pou r them out when I can and let them dry out, then toss them.

I think that is a pretty good idea myself, and have burned a few rags where I can. It is an instant kill shot on the problem and lets you go on your way with one less worry.

Robert

I tend to throw them in a bucket with water and Dawn then dry them out and throw away. That is if I do not burn them yes.

i guess synthetics have a lot more energy in them but once they have set they are pretty stable

I just throw them over stuff in the shop. They're only dangerous if they can't air cool.

i thought that the boiled variety had some special characteristics but i do not recall what they are perhaps the boiling causes the chains to link together in larger than naturally occuring chains and makes the curing process proceed further into its stable finished form

i have left mine on the bricks to dry

an article i read seemed to imply that even when dried and stable it had increased combustability

Electric Comet wrote in news:mr8k79$khj$1 @dont-email.me:

"Boiled" linseed oil dries faster (raw linseed oil takes a very long time to dry). Today, no-one boils oil, instead they add a metallic catalyst which has the same effect.

I'd be dubious that wood finished with linseed oil, or anything else for that matter, is any more combustable than unfinished wood. Once it's ignited, tho, finished wood will burn hotter than unfinished wood.

John