Date: Wed, 24 Sep 2003 12:33:35 -0500

Author: Tom Kramer

Subject: Re: linseed oil (was exothermic/endothermic)

Post:

Linseed oil does not evaporate to dry, it
polymerizes by an oxidation reaction which is
exothermic. It is common to dilute linseed oil
with turpentine to get better penetration of the
wood surface. if you take these linseed oil and
turpentine rags and ball them up, you have an
adiabatic system in the center of the ball with a
mixture of the linseed oil with a high surface
area in contact with air and turpentine. The
linseed oil will polymerize quickly, releasing
heat which cannot escape. The turpentine has a
very low flash point (30-35C) and soon burns.

Tom

>OK, now you've sparked my interest! Why does
>linseed oil GENERATE heat as it dries? This
>can't be simple evaporation going on here.....
>
>Gotta love these meandering topics...
>
>Prue
>
>>Linseed oil soaked materials may spontaneously
>>ignite. Linseed Oil generates heat as it dries
>>(an EXOTHERMIC reaction). This heat generated
>>as it dries can cause spontaneous ignition of
>>materials contacted by Linseed Oil. Oily rags
>>or waste and other oily materials can cause
>>spontaneous combustion fires if not handled
>>properly. Immediately after use, and before
>>disposal or storage, you MUST (1) spread out
>>all oily materials outside to dry by flattening
>>them out to their full size in an any spot for
>>24 hours at temperatures above 40 F.
>>Fred
>>
>>Dr. Fredrick M. Stein
>>Director of Education and Outreach
>>American Physical Society
>>One Physics Ellipse
>>College Park, MD 20740-3844
>>(301) 209-3263
>>(301) 209-0865 fax
>>stein@aps.org
>>http://www.aps.org/educ/
>>
>>>>> reberg@physics.umd.edu 09/24/03 09:35AM >>>
>>I am not a chemist, but isn't this what happens if you leave a rag
>>saturated with linseed oil in a confined place? I use linseed oil on my
>>outdoor lawn furniture, and noticed the warnings about not leaving cloths,
>>brushes, etc. soaked with linseed oil around because of the danger of
>>spontaneous combustion. I have read some of the warning stuff that comes
>>with virtually every chemical (including water!), so I really didn't
>>believe that stuff, UNTIL I TRIED IT. Truly frightening. A linseed oil
>>soaked rag in a bag actually bursts into flame in a very short time.
>>
>>Dick Berg
>>
>
>--
>
>
>
>***********************************
>Prue Schran, Lecturer
>Department of Physics and Astronomy
>Swarthmore College
>Swarthmore, PA 19081-1390
>pschran1@swarthmore.edu
>(610)690-6886 office
>(610)328-7895 fax
>***********************************
>
>"The number you have dialed is
>imaginary. Rotate phone 90 degrees
>and try again."

From pauld@exploratorium.edu Wed Sep 24 12:23:44 2003

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