Hi,

I'm currently writing an article for a canadian woodworking magazine
about fire hazards in a typical workshop. The article will discuss
passive and active measures to take to avoid or extinguish fire.

I would like to make a test with rags soaked with oil and see how long
it would take before it catches fire. I'm wondering which oil is
generating the most heat (tung oil, linseed oil, danish, etc.) and how
long it takes, based on your experience (if you had any), to get the
smoke or an actual flame.

I would also be interested in knowing any experiences with dust
collector fires. There is obviously static electricity but I prefer to
hear about any kind of "accidents" that might have happened and sent a
spark in your dust collector to later on, catch fire. Again, I would
be interested in knowing how long it takes before you do get the smoke
to figure out something's wrong. I know it can be a couple hours.

Feel free to add any other fire hazards you've come across that I may
just overlook at the moment.

Thanks,


Greg D.

P.S.: There is obviously the chemical storage which are also a
concern.

"Greg D." wrote in message
...
Hi,

I'm currently writing an article for a canadian woodworking magazine
about fire hazards in a typical workshop. The article will discuss
passive and active measures to take to avoid or extinguish fire.

I would like to make a test with rags soaked with oil and see how long
it would take before it catches fire. I'm wondering which oil is
generating the most heat (tung oil, linseed oil, danish, etc.) and how
long it takes, based on your experience (if you had any), to get the
smoke or an actual flame.

I would also be interested in knowing any experiences with dust
collector fires. There is obviously static electricity but I prefer to
hear about any kind of "accidents" that might have happened and sent a
spark in your dust collector to later on, catch fire. Again, I would
be interested in knowing how long it takes before you do get the smoke
to figure out something's wrong. I know it can be a couple hours.

Feel free to add any other fire hazards you've come across that I may
just overlook at the moment.

Thanks,


You might contact your local fire department for accurate information.

"Greg D." wrote in message
...
Hi,

I'm currently writing an article for a canadian woodworking magazine
about fire hazards in a typical workshop. The article will discuss
passive and active measures to take to avoid or extinguish fire.

I would like to make a test with rags soaked with oil and see how long
it would take before it catches fire. I'm wondering which oil is
generating the most heat (tung oil, linseed oil, danish, etc.) and how
long it takes, based on your experience (if you had any), to get the
smoke or an actual flame.


One assumes, from the lack of woodworking knowledge -"Danish" is a pastry
not an oil - that you must be a writer, then such things as subject/verb
agreement and capitalization put the lie to that.

I'm with Leon. All this has been done and should be available from say, CSA
among others. I think this kind of work might be too dangerous for you.

On Sun, 22 Oct 2006 11:25:04 GMT, "George" wrote:


One assumes, from the lack of woodworking knowledge -"Danish" is a pastry
not an oil - that you must be a writer, then such things as subject/verb
agreement and capitalization put the lie to that.

Gheeez, I meant danish oil. Just for your information, I'm not "just a
writer" but also a woodworker. Magazines are not all written by people
not knowing a damn about woodworking... It just happen that English is
not my primary language...


I'm with Leon. All this has been done and should be available from say, CSA
among others. I think this kind of work might be too dangerous for you.


The reason why I posted this request was to get some feedback about
potential risks of fire in a typical workshop based on your
experiences or what you may have heard on the subject. Obviously, you
didn't understand that at all from my initial post.

Maybe you should read and understand before making an ass of yourself
by "assuming" things that aren't even remotely close to the truth. Or,
you could have kept your month shut if you had nothing to say.

Greg D.

"Greg D." wrote in message
...


The reason why I posted this request was to get some feedback about
potential risks of fire in a typical workshop based on your
experiences or what you may have heard on the subject. Obviously, you
didn't understand that at all from my initial post.


Hey Greg - I have to confess, when I first read your original post I was a
bit put off. I thought that the last thing I really wanted to see was
another uninformed "reality/experience" article. There are so many of those
kinds of articles out there that although perhaps well intended, do nothing
more than perpetuate myths and misunderstandings. Experiences such as would
be found in a group like this more often reflect anecdotal data and/or
assumptions based on an incomplete investigative process. The net is a
preponderance of poor conclusions. No point in propgating this type of
thing.

Just my thoughts - sorry that they don't support your efforts. I'd really
rather see a more scientific approach to workshop hazards than is likely to
come from what we could give you. Most of us are comfortable with a close
to accurate understanding of what might have happened in a particular
incident and chose not to do that again. It works, but for the sake of an
article I think your readers would deserve more accurate information.

--

-Mike-

"Greg D." wrote in message

Maybe you should read and understand before making an ass of yourself
by "assuming" things that aren't even remotely close to the truth. Or,
you could have kept your month shut if you had nothing to say.

Greg D.

OK, that should get you many contributions towards your writing. Maybe
we'll all keep our "month" shut.

Greg D. wrote in news:nukkj2de2o7jm3gctavu5un1cp08esd73l@
4ax.com:

Hi,

I'm currently writing an article for a canadian woodworking magazine
about fire hazards in a typical workshop. The article will discuss
passive and active measures to take to avoid or extinguish fire.

I would like to make a test with rags soaked with oil and see how long
it would take before it catches fire. I'm wondering which oil is
generating the most heat (tung oil, linseed oil, danish, etc.) and how
long it takes, based on your experience (if you had any), to get the
smoke or an actual flame.

I would also be interested in knowing any experiences with dust
collector fires. There is obviously static electricity but I prefer to
hear about any kind of "accidents" that might have happened and sent a
spark in your dust collector to later on, catch fire. Again, I would
be interested in knowing how long it takes before you do get the smoke
to figure out something's wrong. I know it can be a couple hours.

Feel free to add any other fire hazards you've come across that I may
just overlook at the moment.

Thanks,


Greg D.

P.S.: There is obviously the chemical storage which are also a
concern.

Googling for "oil rag fire" I found this site from Norway:
http://www.sintef-group.com/content/...epslanguage=EN
Seems the risk is being downplayed in Norway. Of course, it might be
catastrophic if it does happen to you. So don't look into the gastank
with a burning cigaret in your mouth ...

--
Best regards
Han
email address is invalid

Hi Mike,

I clearly understand that usenet is like talking with a bunch of
friends. It's in no way scientific or the truth but I believe it's a
very interesting way to come up with unexpected aspects of a subject I
may not have think about in the first place alone. It just opens up my
horizons and gives more depth to my articles.

All my articles are built in the same way. I gather every aspect I
want to cover on the subject and organize them in categories or topics
and then I write the article.

I never rely on newsgroup as per say to write articles but once and a
while, when I'm looking for a source of inspiration I find it tempting
to ask around here.

Unfortunately, each time I do it, I end up clarifying my initial post
because people don't read it (or don't make the effort to understand)
or they try to make me say something I never said.

In other words, 9.9 times out of 10, it's a complete waste of time
because it won't turn out anything useful aside from a great amount of
sarcams and false assumptions when it's not just plain insults.

Since I'm a very optimistic person, I always believe (I'm certainly
still too naive) that a few persons can discuss on a subject and bring
some interesting arguments and explanations. This discussion this
morning just prove the opposite again and it's certainly why, among
other things, a lot of very interesting people with something to say
and share eventually shut up and quit rec.woodworking. When one have
nothing to say, share or have no opinion on a subject, it would just
be logical they don't post especially if their answers are intented to
turn the initial poster into an idiot.

On the other hand, I would like to thank all those of you who did make
an effort to share some information like Han who provided a link to
useful information.

Thanks,


Greg D.




On Sun, 22 Oct 2006 08:13:55 -0400, "Mike Marlow"
wrote:


"Greg D." wrote in message
.. .


The reason why I posted this request was to get some feedback about
potential risks of fire in a typical workshop based on your
experiences or what you may have heard on the subject. Obviously, you
didn't understand that at all from my initial post.


Hey Greg - I have to confess, when I first read your original post I was a
bit put off. I thought that the last thing I really wanted to see was
another uninformed "reality/experience" article. There are so many of those
kinds of articles out there that although perhaps well intended, do nothing
more than perpetuate myths and misunderstandings. Experiences such as would
be found in a group like this more often reflect anecdotal data and/or
assumptions based on an incomplete investigative process. The net is a
preponderance of poor conclusions. No point in propgating this type of
thing.

Just my thoughts - sorry that they don't support your efforts. I'd really
rather see a more scientific approach to workshop hazards than is likely to
come from what we could give you. Most of us are comfortable with a close
to accurate understanding of what might have happened in a particular
incident and chose not to do that again. It works, but for the sake of an
article I think your readers would deserve more accurate information.

"Greg D." wrote in message
Unfortunately, each time I do it, I end up clarifying my initial post
because people don't read it (or don't make the effort to understand)
or they try to make me say something I never said.

In other words, 9.9 times out of 10, it's a complete waste of time
because it won't turn out anything useful aside from a great amount of
sarcams and false assumptions when it's not just plain insults.

Since I'm a very optimistic person, I always believe (I'm certainly
still too naive)

it would just
be logical they don't post especially if their answers are intented to
turn the initial poster into an idiot.

Yes, you are still naive. After insulting most of the group, most of the
group are just too polite to tell you to f-- off. You are making a lot of
friends here.

On Sun, 22 Oct 2006 13:58:49 GMT, "Edwin Pawlowski"
wrote:


Yes, you are still naive. After insulting most of the group, most of the
group are just too polite to tell you to f-- off. You are making a lot of
friends here.

Thank you for confirming exactly the problem I'm trying to describe.

I ask a question, I get stupid answers. I clarify it, I get even more
stupid and insulting answers. What else can I say? Try reading my
initial post and see if it deserved insults in the first place. I
think not but it seems I'm the only one thinking that way.

Then, I will follow your wise advice and just **** off from here.


Greg D.

"Greg D." wrote in message

Thank you for confirming exactly the problem I'm trying to describe.

I ask a question, I get stupid answers. I clarify it, I get even more
stupid and insulting answers. What else can I say? Try reading my
initial post and see if it deserved insults in the first place. I
think not but it seems I'm the only one thinking that way.

Initial post was OK. Your follow ups were not something that would make
your mother proud. Learn to ignore rather than retaliate and you will still
get those little gems of knowledge you seek. Make one nasty personal remark
and you turn off many potential responders.

Newsgroups is a tough neighborhood.

Greg D. wrote:

I would like to make a test with rags soaked with oil and see how long
it would take before it catches fire.

Not long - only a few hours (depending on time of day). I've never
seen a fire caused by this, but I have had my own wadded rags start to
smoulder during a UK Summer (maybe 35°C in my workshop). The riskiest
time is the crossover between hottest part of the day, and an hour or
so after the oil was applied. Once they've cured for a few hours on a
hot day they'll start to cool down.

The expert on this stuff is Bill Knight the muzzle loader. He's the
author of the best monograph out there on historical linseed oil driers
and oil curing.

Greg D. wrote:
: Hi,

: I'm currently writing an article for a canadian woodworking magazine
: about fire hazards in a typical workshop. The article will discuss
: passive and active measures to take to avoid or extinguish fire.

: I would like to make a test with rags soaked with oil and see how long
: it would take before it catches fire. I'm wondering which oil is
: generating the most heat (tung oil, linseed oil, danish, etc.) and how
: long it takes, based on your experience (if you had any), to get the
: smoke or an actual flame.

One problem in doing an accurate estimate is degree of
crumple in the rag or paper towel. The fire is caused by heat
generated by the oil oxidizing, and that is going to be influenced
by amount of surface area open to oxygen.


: Feel free to add any other fire hazards you've come across that I may
: just overlook at the moment.


Here's a couple:

1) Steel wool. Quite flammable (huge amount of surface area for thin wire).
I've heard of a few fires caused by the stuff catching a grinder spark.


2) Grinding both aluminum and steel on the same
grinding wheel can create thermite. This can cause the wheel to
explode. Lee Valley is a good contact for this - -they had an
article on their website about a specific occurrence.


Looking forward to your article (where will it appear?).

-- Andy Barss

In article , Greg D. wrote:
[snip]

Unfortunately, each time I do it, I end up clarifying my initial post
because people don't read it (or don't make the effort to understand)
or they try to make me say something I never said.

I believe it was William Zinsser, in "On Writing Well," who said that the
purpose of writing is not to make yourself understood -- but to make it
impossible to be misunderstood.

In other words, 9.9 times out of 10, it's a complete waste of time
because it won't turn out anything useful aside from a great amount of
sarcams and false assumptions when it's not just plain insults.

If you find that your writing is so consistently misunderstood, that should
perhaps suggest which direction you should explore to correct the problem.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article , Greg D. wrote:

Gheeez, I meant danish oil.

Does that come from the danish tree?

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article , Greg D. wrote:

I ask a question, I get stupid answers. I clarify it, I get even more
stupid and insulting answers. What else can I say? Try reading my
initial post and see if it deserved insults in the first place. I
think not but it seems I'm the only one thinking that way.

Then, I will follow your wise advice and just **** off from here.

Don't let the door hit ya in the butt on your way out.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Sat, Oct 21, 2006, 1:17pm (Greg*D.) doth come in and
mumbles:
snip I would like to make a test with rags soaked with oil and see how
long it would take before it catches fire. I'm wondering which oil is
generating the most heat (tung oil, linseed oil, danish, etc.) and how
long it takes, based on your experience (if you had any), to get the
smoke or an actual flame. snip

OK, so go ahead and do it.

This stuff has been beat to death, here and elsewhere. All you
have to do is check.

As for asking here, my rule is, in this order:
1. Check every where I can.
2. Ask my mother.
3. Ask here.
Always worked so far.



JOAT
It's not hard, if you get your mind right.
- Granny Weatherwax

Doug Miller wrote:
In article , Greg D. wrote:

Gheeez, I meant danish oil.

Does that come from the danish tree?


No, Danish nuts.

--

FF

On Sun, 22 Oct 2006 17:08:32 +0000 (UTC), Andrew Barss
wrote:

Here's a couple:

1) Steel wool. Quite flammable (huge amount of surface area for thin wire).
I've heard of a few fires caused by the stuff catching a grinder spark.


2) Grinding both aluminum and steel on the same
grinding wheel can create thermite. This can cause the wheel to
explode. Lee Valley is a good contact for this - -they had an
article on their website about a specific occurrence.

Wow! This is something very interesting! Thank you very much.

I found the said article in the sharpening section of Lee Valley's
website.


Thank you very much,

Greg D.




Looking forward to your article (where will it appear?).

-- Andy Barss

Andrew Barss wrote in news:ehg8ig$6hl$1
@onion.ccit.arizona.edu:

2) Grinding both aluminum and steel on the same
grinding wheel can create thermite. This can cause the wheel to
explode. Lee Valley is a good contact for this - -they had an
article on their website about a specific occurrence.


I was told that this reaction was used to repair/fuse tracks for electric
trolleys (Dutch word is "tram", it is similar to the "light rail" system in
for instance Hoboken, NJ and surrounding).

Another explanation of the reaction between rust and aluminium (with either
1 or 2 "i"s) is he
http://www.ilpi.com/genchem/demo/thermite/index.html

--
Best regards
Han
email address is invalid

"J T" wrote in message

As for asking here, my rule is, in this order:
1. Check every where I can.
2. Ask my mother.
3. Ask here.
Always worked so far.


Great idea, but I don't have your mother's phone number.

Han wrote:

Another explanation of the reaction between rust and aluminium

You can't make a thermite reaction using alumium and mere rust -- it's
the wrong iron oxide. You certainly can do it with grinding wheels,
although the usual reaction is merely some unusually bright sparks.


(Yes, alumium. I'm a Humphry Davy fanboy)

Andy Dingley wrote:
Han wrote:

Another explanation of the reaction between rust and aluminium

You can't make a thermite reaction using alumium and mere rust -- it's
the wrong iron oxide. You certainly can do it with grinding wheels,
although the usual reaction is merely some unusually bright sparks.

True. An explosion is unlikely. I have made thermite from rusty nails
and aluminum scrapings though. It burns about as bright as magnesium.

An unexpected source of fire that I experienced was using a grinding
wheel on a grinder that also had a cloth buffing wheel attached.
Fibers would fly off the buffing wheel and gather in the dust collector
port. Then a spark from the grinding wheel would ignite it. Once the
fire gets pulled into the dust collector then you've got a full blown
inferno in your cyclone.

"Han" wrote in message
...
Andrew Barss wrote in news:ehg8ig$6hl$1
@onion.ccit.arizona.edu:

2) Grinding both aluminum and steel on the same
grinding wheel can create thermite. This can cause the wheel to
explode. Lee Valley is a good contact for this - -they had an
article on their website about a specific occurrence.


I was told that this reaction was used to repair/fuse tracks for electric
trolleys (Dutch word is "tram", it is similar to the "light rail" system
in
for instance Hoboken, NJ and surrounding).

Another explanation of the reaction between rust and aluminium (with
either
1 or 2 "i"s) is he
http://www.ilpi.com/genchem/demo/thermite/index.html

There's a TV series, "Brainiac", in which they regularly apply thermite to
various objects.

Stuff will burn through just about anything.

In article .com,
wrote:

Andy Dingley wrote:
...snipped...
An unexpected source of fire that I experienced was using a grinding
wheel on a grinder that also had a cloth buffing wheel attached.
Fibers would fly off the buffing wheel and gather in the dust collector
port. Then a spark from the grinding wheel would ignite it. Once the
fire gets pulled into the dust collector then you've got a full blown
inferno in your cyclone.


At least the metal particles keep the static charge from building up
and causing an explosion...

--
No dumb questions, just dumb answers.

Larry Wasserman - Baltimore, Maryland -

Greg D. wrote:

I would like to make a test with rags soaked with oil and see how long
it would take before it catches fire. I'm wondering which oil is
generating the most heat (tung oil, linseed oil, danish, etc.) and how
long it takes, based on your experience (if you had any), to get the
smoke or an actual flame.

I've tried it a few times with boiled linseed oil and once with tung
oil but I've never managed to even get smoke. All my attempts have
been used with rags cut from old cotton T-shirts that have been used
to apply a finish. I've left them crumpled in plastic cups both inside
(under observation) and out in the sun on a hot day for up to about 6
hours. I suspect my rags were just too small but until I can manage to
get a reaction it's just a guess. I'd be interested in hearing the
conditions that are required to get an actual fire going.

Ken Muldrew

(remove all letters after y in the alphabet)

Mon, Oct 23, 2006, 2:14am (EDT+4) (Edwin*Pawlowski) doth
sayeth:
Great idea, but I don't have your mother's phone number.

Just as well, she gives lousy advice.



JOAT
If it can't kill you, it ain't a sport.

Tue, Oct 24, 2006, 6:16pm (EDT+4) (Ken*Muldrew)
doth sayeth:
snip I've left them crumpled in plastic cups both inside (under
observation) and out in the sun on a hot day for up to about 6 hours.
snip

I haven't checked, but I'd suspect it might take longer than six
hours. In any event, I wouldn't want to take chances on it not
happening.



JOAT
If it can't kill you, it ain't a sport.

J T wrote:
Tue, Oct 24, 2006, 6:16pm (EDT+4) (Ken Muldrew)
doth sayeth:
snip I've left them crumpled in plastic cups both inside (under
observation) and out in the sun on a hot day for up to about 6 hours.
snip

I haven't checked, but I'd suspect it might take longer than six
hours. In any event, I wouldn't want to take chances on it not
happening.

One of the local tv stations or maybe it was 60-60 or 20 minutes
ran a story on the spontaneous combustion of linseed oil
soaked rags. They put theirs insider of a corrugated cardboard
box to help it retain heat wihout cutting off oxygen and put it
in the sun. It took several hours but caught fire the same day,
IIFC.

But I think the time to ignition is going to vary wuite a lot
on conditions, the type of and concentration of driers
in the oil, the age of the oil and so on.

One person posted in here that he hung a linseed oil
soaked rag on a closeline in the sun and it caught fire
within a couple of hours. I find that hard to believe.

'Overnight' has been long enough to burn a few buildings
down.

--

FF

(J T) wrote:

Tue, Oct 24, 2006, 6:16pm (EDT+4) (Ken=A0Muldrew)
doth sayeth:
snip I've left them crumpled in plastic cups both inside (under
observation) and out in the sun on a hot day for up to about 6 hours.
snip

I haven't checked, but I'd suspect it might take longer than six
hours.

That was 6 hours in the sun. The cups were left on concrete blocks
forming the rim of a firepit so I just left them there until the rags
became stiff.

In any event, I wouldn't want to take chances on it not
happening.

Full agreement; I'm always very careful. I would still like to be able
to reproduce the phenomenon, though.

Ken Muldrew

(remove all letters after y in the alphabet)

"Ken Muldrew" wrote in message
...
(J T) wrote:

Tue, Oct 24, 2006, 6:16pm (EDT+4) (Ken=A0Muldrew)
doth sayeth:
snip I've left them crumpled in plastic cups both inside (under
observation) and out in the sun on a hot day for up to about 6 hours.
snip

I haven't checked, but I'd suspect it might take longer than six
hours.

That was 6 hours in the sun. The cups were left on concrete blocks
forming the rim of a firepit so I just left them there until the rags
became stiff.

In any event, I wouldn't want to take chances on it not
happening.

Full agreement; I'm always very careful. I would still like to be able
to reproduce the phenomenon, though.


Sheesh! One would suppose the participants would have taken the advice given
earlier to the OP and LOOKED IT UP!

http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd189_e.html

We may presume that the same conditions obtain south of the border.

"George" wrote:


"Ken Muldrew" wrote in message
...
(J T) wrote:

Tue, Oct 24, 2006, 6:16pm (EDT+4) (Ken=A0Muldrew)
doth sayeth:
snip I've left them crumpled in plastic cups both inside (under
observation) and out in the sun on a hot day for up to about 6 hours.
snip

I haven't checked, but I'd suspect it might take longer than six
hours.

That was 6 hours in the sun. The cups were left on concrete blocks
forming the rim of a firepit so I just left them there until the rags
became stiff.

In any event, I wouldn't want to take chances on it not
happening.

Full agreement; I'm always very careful. I would still like to be able
to reproduce the phenomenon, though.


Sheesh! One would suppose the participants would have taken the advice given
earlier to the OP and LOOKED IT UP!

Calm yourself, George, there's no reason to get overly excited. We're
just having a friendly chat here. This isn't a crisis line or anything
like that.

http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd189_e.html

We may presume that the same conditions obtain south of the border.

Unfortunately they don't give the conditions; just some general
principles. As you can see from the quoted material above, cotton rags
soaked in linseed oil and left out in the sun do not always
spontaneously ignite. So the question was asked whether anyone knew of
a specific set of circumstances where such material would ignite. We
appreciate your efforts in LOOKING IT UP and we do hope that you
continue until you have a successful recipe to share.

Ken Muldrew

(remove all letters after y in the alphabet)

"Greg D." wrote in message
...
Hi,

I'm currently writing an article for a canadian woodworking magazine
about fire hazards in a typical workshop. The article will discuss
passive and active measures to take to avoid or extinguish fire.

I would like to make a test with rags soaked with oil and see how long
it would take before it catches fire. I'm wondering which oil is
generating the most heat (tung oil, linseed oil, danish, etc.) and how
long it takes, based on your experience (if you had any), to get the
smoke or an actual flame.

I would also be interested in knowing any experiences with dust
collector fires. There is obviously static electricity but I prefer to
hear about any kind of "accidents" that might have happened and sent a
spark in your dust collector to later on, catch fire. Again, I would
be interested in knowing how long it takes before you do get the smoke
to figure out something's wrong. I know it can be a couple hours.

Feel free to add any other fire hazards you've come across that I may
just overlook at the moment.

Thanks,


Greg D.

P.S.: There is obviously the chemical storage which are also a
concern.

For some reason I woke up this morning thinking about this discussion (mind
works in mysterious ways). I realize it's a bit late but here goes.

Most people seek to avoid spontaneous combustion so I think you'll find
little real experience with it among woodworkers, and certainly none at the
level that you're looking for--most of us who have had one experience with
it consider that enough for a lifetime and don't continue to make the same
mistakes of storage that would let us gather enough anecdotal data to be
able to compare different finishes.

That said, I'm not sure your question really has an answer. The time to
combust depends on too many variables. To take a couple of extremes, hang
an oil-soaked rag on a clothesline and toss a bunch of wadded up rags into a
barrel of oil. Neither will combust no matter how long you leave them. The
rag on the clothseline has plenty of oxygen, but it also has a lot of
surface exposed to free convection--that keeps it cool enough to not
combust, or even get perceptibly warmer than an adjacent dry rag. The rags
in the oil barrel aren't exposed to oxygen at all, so they don't heat.

To get spontaneous combustion you need a lot of oily surface exposed to air,
but also need to have that air trapped so that it acts as an insulator and
you need enough thickness of insulation to hold in the heat. How soon it
happens depends on how oily the rags are and in what quanntity and how
tightly wadded--too oily and it won't happen, not oily enough and it won't
happen, too tightly wadded it won't happen, not tightly enough it won't
happen, not _enough_ of it wadded up and it won't happen and in the range in
which it will happen there's a range from "barely goes" to "goes right
quick".

In article , "J. Clarke" wrote:
Very well said...

Most people seek to avoid spontaneous combustion so I think you'll find
little real experience with it among woodworkers, and certainly none at the
level that you're looking for--most of us who have had one experience with
it consider that enough for a lifetime and don't continue to make the same
mistakes of storage that would let us gather enough anecdotal data to be
able to compare different finishes.

... especially that part. LOL but you make an excellent point.

That said, I'm not sure your question really has an answer. The time to
combust depends on too many variables. To take a couple of extremes, hang
an oil-soaked rag on a clothesline and toss a bunch of wadded up rags into a
barrel of oil. Neither will combust no matter how long you leave them. The
rag on the clothseline has plenty of oxygen, but it also has a lot of
surface exposed to free convection--that keeps it cool enough to not
combust, or even get perceptibly warmer than an adjacent dry rag. The rags
in the oil barrel aren't exposed to oxygen at all, so they don't heat.

To get spontaneous combustion you need a lot of oily surface exposed to air,
but also need to have that air trapped so that it acts as an insulator and
you need enough thickness of insulation to hold in the heat.

I think "confined" might be a better word than "trapped" -- after all, if the
rags are in an *airtight* container (where the air is certainly "trapped")
there won't be any combustion, because there is not enough available oxygen.
Unless the container is large enough in comparison to the volume of oily
rags... which of course is yet *another* variable to consider...

How soon it
happens depends on how oily the rags are and in what quanntity and how
tightly wadded--too oily and it won't happen, not oily enough and it won't
happen, too tightly wadded it won't happen, not tightly enough it won't
happen, not _enough_ of it wadded up and it won't happen and in the range in
which it will happen there's a range from "barely goes" to "goes right
quick".

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.