Be Careful Out There, Hear

[ken hatch]

Damn Bubba you almost burned the house down. The shop was still hot from the day and I had it closed up so it wasn't cooling off. I'd wiped the tool chest lid once more with the BLO soaked rag before taking a short break for some tea and a cool down. I left the rag bunched and on the top of the tool chest while I cooled off. As I was going back to the shop I noticed a smell and my eyes were burning, it was stronger in the shop but there was no smoke. I looked around and noticed the BLO rag. When I picked it up it was very warm, unfolding it reviled black burned areas. Here is a photo of the rag:

http://i257.photobucket.com/albums/hh222/VTXAZ/toolBoxBurnedBLORag160605_zpsl9gwi41o.jpg

I couldn't have been out of the shop more than 45 minutes to an hour and it was a single rag setting in the open. Normally once I finish with a rag I'll put it in a metal bucket filled with water until I can dump them in the trash but even that will be no more. If I am going to leave the shop for any reason finished or not with the rag it is going in the bucket and I'll make sure the bucket has enough water to cover the rags.

ken

[David Wong]

Wow. Glad you caught it in time. A really graphic reminder to be careful.

[Patrick Chase]

I left the rag bunched and on the top of the tool chest while I cooled off

The key word here is "bunched".

When you did that you took a large volume of polymerizing oil and shaped it so that it didn't have much exposed surface area. Polymerization is exothermic, and that heat must either dissipate via the exposed surface or warm up the interior. When you bunched the rag you created a configuration that couldn't dissipate the heat, so it warmed up instead. Whether the rag is wadded/bunched is more important than the other factors you cite (single vs multiple, inside vs out, etc).

You are very lucky, as the time window from "smell smoke" to "ignition" isn't long.

[Stanley Covington]

The key word here is "bunched".

When you did that you took a large volume of polymerizing oil and shaped it so that it didn't have much exposed surface area. Polymerization is exothermic, and that heat must either dissipate via the exposed surface or warm up the interior. When you bunched the rag you created a configuration that couldn't dissipate the heat, so it heated instead. Whether the rag is wadded/bunched is more important than the other factors you cite (single vs multiple, inside vs out, etc).

You are very lucky, as the time window from "smell smoke" to "ignition" isn't long.

Thanks for the explanation, Patrick. Clears up some questions I had.

Stan

[Frederick Skelly]

Man, that's scary Ken. Very glad you caught it in time!
Fred

[Mike Cherry]

Truly scary. Good thing you were home and around the shop.

[Mike Holbrook]

Good post Ken, we certainly need to remind ourselves of that danger on a regular basis as your picture so graphically does.

[ken hatch]

Thanks Guys,

I'm glad I went back to the shop but if I hadn't planned to go back the rag would have been in the bucket and would not have been a problem. The major takeaway for me was just how quickly it reached combustion.

ken

[James Pallas]

Ken, glad to hear you didn't suffer any greater loss. This oil stuff is indeed dangerous. My experience was also in the desert SW (New Mexico). Rags that had been used to wipe Watco Danish oil. Hung over a pallet stretched out, outdoors. Warm and dry, not terrible hot, maybe eighty or so. Went up in a blaze. I don't know the chemistry and don't care, all oil rags go in the water immediately after used up, no drying out, no reuse. Too risky for me. I don't think anyone can give a fool proof theory other than in the water or purposely and carefully burn up.
Jim

[Jim Koepke]

I will leave tools and scraps where they lay when taking a break, but never a rag with BLO or other finishes.

Glad to hear it was only a close call reminder.

jtk

[ken hatch]

The key word here is "bunched".

When you did that you took a large volume of polymerizing oil and shaped it so that it didn't have much exposed surface area. Polymerization is exothermic, and that heat must either dissipate via the exposed surface or warm up the interior. When you bunched the rag you created a configuration that couldn't dissipate the heat, so it warmed up instead. Whether the rag is wadded/bunched is more important than the other factors you cite (single vs multiple, inside vs out, etc).

You are very lucky, as the time window from "smell smoke" to "ignition" isn't long.

Patrick,

Yep, I know and thought I understood all that, in fact I thought I was following "best practices". Shame on me....I never thought it could heat to combustion that quickly. The time from taking the last wipe, walking inside the house, drinking a glass of iced tea and then returning to the shop couldn't have been more than 45 minutes, if that.

Dodged the bullet once, it will not get a second chance.

ken

[ken hatch]

Ken, glad to hear you didn't suffer any greater loss. This oil stuff is indeed dangerous. My experience was also in the desert SW (New Mexico). Rags that had been used to wipe Watco Danish oil. Hung over a pallet stretched out, outdoors. Warm and dry, not terrible hot, maybe eighty or so. Went up in a blaze. I don't know the chemistry and don't care, all oil rags go in the water immediately after used up, no drying out, no reuse. Too risky for me. I don't think anyone can give a fool proof theory other than in the water or purposely and carefully burn up.
Jim

James,

That is my normal routine, I have an old metal milk pail that I keep half full of water just to hold oil rags until I can take 'em to the outside trash bucket. But I would not put 'em in the bucket until I had finished what ever use I had for the rag or shut the shop down for the day. New routine: If I walk out of the shop, even just to get a drink of water or whatever, the used rag is going into the water bucket and I will start over when I come back.

ken

[Dave Beauchesne]

Not to hi-jack the thread, but a buddy was in his stand alone shop one evening - he was vacuuming with a shop vac and the power went out. Went into the house - got about some other things with the power out - eventually went to bed.

Got up the next day, went to the shop ( power had been restored ) and it was about 100F in the shop - vacuum was running and smelling very hot. The sides of the plastic motor cover were starting to sluff - could have easily caught on fire. Of course, he didn't unplug it when the power went off.

Just another reminder of shop safety. Glad this rag didn't burn down the house !!!

Dave B

[Brad Barnhart]

Wow! Glad it didn't damage your work piece, hoss. My shop is pretty small, tools on every wall, 2 lathes, what have ya. I use Watco finishes regularly. When I'm done with a project, I always drape the rag over one of the lathes, or over the end of the RAS until it dries, then throw the rag in the trash. I haven't had any issues that way. You had a good eye opener, Mr. Ken. God bless & take care.

[Patrick Chase]

Ken, glad to hear you didn't suffer any greater loss. This oil stuff is indeed dangerous. My experience was also in the desert SW (New Mexico). Rags that had been used to wipe Watco Danish oil. Hung over a pallet stretched out, outdoors. Warm and dry, not terrible hot, maybe eighty or so. Went up in a blaze. I don't know the chemistry and don't care, all oil rags go in the water immediately after used up, no drying out, no reuse. Too risky for me. I don't think anyone can give a fool proof theory other than in the water or purposely and carefully burn up.
Jim

The nominal autoignition temperature for an "oil-soaked rag" with light mineral/distillate oil (one that doesn't polymerize and doesn't contribute any heat of its own) is only about 150F IIRC. You could easily get there in direct sunlight on the wrong surface, even at fairly modest air temperatures as you describe.

Also "stretched out on a pallet" or any other insulating surface will cause about 2X as much temperature rise from polymerization as hanging with both sides exposed to air. Half the radiative surface area means double the temperature rise.

Probably the best solution I've heard is one George described: Stretch the rag out on a metal trash-can lid. The metal lid acts as a radiator with greater surface area than the rag, so it's even better than hanging with both sides exposed, and it also acts as a fire barrier if the rag goes anyway.

Water will certainly prevent flare-ups while the rag is immersed, but doesn't that just suspend polymerization (by blocking oxygen) and leave the problem for later, after the water dries out? I don't know the answer, it just seems to me to not be a permanent fix. The oil isn't truly safe until it's full polymerized, right?

[Bryce Adams]

It's clear that rags soaked with drying oils can spontaneously catch fire, and many people put them in a water filled bucket. How do you dispose of a bucket of oily water and rags? If you throw the rags into the trash, is the oil a non-factor once the water evaporates? How do you get rid of the oily water?

I either hang rags on something, or spread them out on the concrete garage floor and throw them out once they are dry. Or I take them out to my fire pit and burn them.

[Jerry Olexa]

Good reminder..be careful...Thanks

[John Schtrumpf]

.... How do you dispose of a bucket of oily water and rags? ...

I use warm soapy water and wash as much oil as I can out of the rags, before I lay them flat on my granite counter to dry. The oily soapy water gets flushed down the drain (same as any other vegetable / animal oil). Oh, and I use the smallest pieces of rags that will do the job.

Edit: Also, I only use pure oils (linseed, tung, walnut) with no solvents.

[bridger berdel]

I drape oily rags over the anvil. I think that 100 lbs of steel is a sufficiently flame resistant heat sink. after they have been there for a few days I'll toss them in the trash.

[Patrick Chase]

I use warm soapy water and wash as much oil as I can out of the rags, before I lay them flat on my granite counter to dry. The oily soapy water gets flushed down the drain (same as any other vegetable / animal oil). Oh, and I use the smallest pieces of rags that will do the job.

Edit: Also, I only use pure oils (linseed, tung, walnut) with no solvents.

Yep, a dispersant or emulsifying agent would render the oil harmless. I amend my previous comment to "it's not safe until it's polymerized or dispersed" :-)

[Steve Voigt]

Ken, glad to hear it was only a close call. Be careful--I'll be pretty pissed if you burn up all those planes! 😂

[Brian Holcombe]

Glad you are ok Ken! Ru Amagasu warned me away from BLO about 10 years ago for that exact reason. I never forgot how incredibly serious he was about it.

[Mike Allen1010]

Wow. Glad you caught it in time. A really graphic reminder to be careful.

+1, I can't help wonder how many times I've been in a similar situation without even knowing it. Thanks for the reminder!

Mike

[Stewie Simpson]

A good reason why I don't use BLO in my workshop.

Stewie;

[ken hatch]

Ken, glad to hear it was only a close call. Be careful--I'll be pretty pissed if you burn up all those planes! 

Most of my woodies were in the tool chest, the epicenter if it had gone much longer. I can't remember if I posted here but Monday I called the Honda shop to check on my '08 Goldwing (The Dirty Fat Girl) only to be told "Oh your 'Wing caught on fire while we were working on it and almost burned our shop down." It hasn't been a great week for myself and fire.

Of the two, I'm glad it was the 'Wing instead of the woodies.

ken

[ken hatch]

Glad you are ok Ken! Ru Amagasu warned me away from BLO about 10 years ago for that exact reason. I never forgot how incredibly serious he was about it.

Brian,

I've long known BLO could be a problem but I've never found any other finish I like as well nor had any close calls with using it. I'll be more aware especially when the shop is hot as it was the other day, my guess the shop was well over 100F at the time.

ken

[Frederick Skelly]

Monday I called the Honda shop to check on my '08 Goldwing (The Dirty Fat Girl) only to be told "Oh your 'Wing caught on fire while we were working on it and almost burned our shop down." It hasn't been a great week for myself and fire.

ken

Holy moly Ken! I guess not! Geez. Does the shop's insurance cover that? (I have my doubts, but maybe so if they caused it.) Can it be repaired suitably?

[Brian Holcombe]

IIRC there are metal containers you can use?

[Patrick Chase]

Brian,

I've long known BLO could be a problem but I've never found any other finish I like as well nor had any close calls with using it. I'll be more aware especially when the shop is hot as it was the other day, my guess the shop was well over 100F at the time.

ken

Same boat here - Polymerizing oils (BLO, Tung) are my favorite choices for an in-the-wood finish. They accentuate well-prepared wood in a way that on-the-surface finishes simply can't. Unfortunately they all share the same issue: Polymerization is exothermic, and oil-soaked rags have a low autoignition point.

IMO the most efficient approach is defense in depth. Stretch the rags out and/or heat-sink them so that they dissipate the heat of polymerization, but also put them somewhere where a fire will be inherently contained. That's why I recommended George's "metal trash can lid, outside on concrete" approach earlier in the thread - it provides both heat-sinking and containment.

Keep in mind here that *any* oil-soaked rag is going to be pretty easy to ignite, even if it isn't generating any heat of its own. Hanging/stretching merely renders a BLO-soaked rag as "safe" as, say, a rag full of light mineral oil. That isn't very safe, which is why you need the second line of defense.

[Marvin Button]

We almost lost an entire furniture factory that way once. We sprayed oil base stain and the boss replaced the filter medium in our spray booth. He left it over night in an old canvas mail cart. The next morning all we had left was the metal frame of the cart and a big black spot on the ceiling. If the ceiling had been any closer the second floor would have caught fire and the rest would have been history.

[Kees Heiden]

The previous owner of our house was a painter and the neighbour told us that he had fire in the garage because of linseed oil rags.

I always lay the rags in the fire pit, thinking that any spontaneous combustion won't harm down there. But I never had a combustion like that (yet).