On 12/19/2013 6:13 PM, DoN. Nichols wrote:
On 2013-12-18, Larry wrote:
On 18 Dec 2013 04:53:45 GMT, "DoN.
wrote:

[ ... ]

And I've never seen a label on the paint warning about shaking
it, but I *have* seen such a warning label about aluminum paint on a
paint shaker bolted to a vertical floor-to-ceiling I-beam at work (a
later job) This was one of the kind which cranks two flat plates down on
each end of the can and shakes it around a horizontal axis through the
middle of the can half way between the two ends.

Do you recall what it said? What type of warning was it? Mess or
explosion?

Just "Do not use to shake aluminum paint!" (in big red letters,
IIRC. :-)

[ ... ]

I'd like to see a real explanation--a quick search on manufacturers'
sites didn't bring anything to light.

I would too. But the one about the "tung oil" makes a certain
amount of sense.

Totally different conditions and reaction than whatever's going on (if
anything) in the can.

I know people who have had smoldering fires from catalyzing oil finish
rags, so it's not just hearsay. I dry mine on the sidewalk for a week
before putting them in a trash can. Why take chances? When they're
hard, they're safe. Wet and crumpled, they get hot to the touch. My
first clue was picking up a hot rag in a cold shop. That brought the
warning home to me.

I've always believed the warnings I learned in elementary school
science class, but I've not worked with those materials. I tend to also
put oily rags in a metal trash can, not a plastic one. :-)

My two favorite wood finishes, Watco and Waterlox, are both catalyzing
oils and prone to that.

O.K. So the remaining question is:f

"How hot can a half-full can of this get if shaken?"
....

_IFF_ (the proverbial "big if") this is actually occurring (of which I'm
still not convinced there's not something else at play) I doubt it's
actually much temperature related (at least from internally generated
heat; the hypothesis of starting w/ something hot from exposure to sun
or the like aside)at all but some sort of outgassing or the like that's
generating the internal pressure rise with some modicum of additional
heat perhaps. If this were such a major issue it seems the cans would
have all sorts of warnings and it wouldn't need just a handwritten sign
on the mixer at the local co-op.

On the tales of spontaneous combustion, HS chemistry teacher used a rag
to wipe some spill from the lab counter after a demonstration in last
class period of day class and hung the rag on a clothes hook and closed
the door in a small closet. Next morning the door was heavily charred
in the area and the rag was mostly ash on the floor. Fortunately, it
appeared that lack of O2 in the small closet prevented full-fledged
fire. He purposely never let maintenance repair the door as a reminder
both to himself and students...was pretty effective teaching aid. I,
also, to this day, am certain to not leave finishing rags in precarious
places.

--