<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:'bookman old style', 'new york', times, serif;font-size:12pt"><div>Wikipedia has a decent discussion under the "linseed oil" heading, including:</div><div><br></div><div><span class="Apple-style-span" style="font-family: sans-serif; font-size: 15.6px; line-height: 20px; ">Having a high content of di- and triunsaturated esters, linseed oil is particularly susceptible to polymerization reactions upon exposure to oxygen in air. This polymerization, which is called "drying," results in the rigidification of the material. The drying process can be so exothermic as to pose a fire hazard under certain circumstances.</span></div><div><span class="Apple-style-span" style="font-family: sans-serif; font-size: 15.6px; line-height: 20px; "><br></span></div><div><span class="Apple-style-span" style="font-family: sans-serif; font-size: 15.6px; line-height: 20px;
"><span class="Apple-style-span" style="line-height: 20px; font-size: 15.6px; ">Rags soaked with linseed oil stored in a pile are considered a fire hazard because they provide a large surface area for <a href="http://en.wikipedia.org/wiki/Oxidation" title="Oxidation" class="mw-redirect" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">oxidation</a> of the oil, and the oil oxidizes quickly. The oxidation of linseed oil is an <a href="http://en.wikipedia.org/wiki/Exothermic" title="Exothermic" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial;
background-repeat: initial initial; ">exothermic</a> reaction, which <a href="http://en.wikipedia.org/wiki/Thermal_runaway" title="Thermal runaway" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">accelerates</a> as the temperature of the rags increases. When heat accumulation exceeds the rate of heat dissipation into the environment, the temperature increases and may eventually become hot enough to make the rags <a href="http://en.wikipedia.org/wiki/Spontaneous_combustion_(combustion)" title="Spontaneous combustion (combustion)" class="mw-redirect" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial;
background-color: initial; background-position: initial initial; background-repeat: initial initial; ">spontaneously combust</a>.</span></span></div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt"><br></div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt">The "drying oil" entry goes into more detail:</div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt"><span class="Apple-style-span" style="font-family: sans-serif; font-size: 15.6px; line-height: 20px; ">A <b>drying oil</b> is an <a href="http://en.wikipedia.org/wiki/Oil" title="Oil" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">oil</a> that hardens to a tough, solid
film after a period of exposure to air. The oil does not harden through the <a href="http://en.wikipedia.org/wiki/Evaporation" title="Evaporation" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">evaporation</a> of water or other <a href="http://en.wikipedia.org/wiki/Solvent" title="Solvent" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">solvents</a>, but through a chemical reaction in which the components crosslink by the action of <a href="http://en.wikipedia.org/wiki/Oxygen" title="Oxygen"
style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">oxygen</a>. Drying oils are a key component of <a href="http://en.wikipedia.org/wiki/Oil_paint" title="Oil paint" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">oil paint</a> and some <a href="http://en.wikipedia.org/wiki/Varnish" title="Varnish" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position:
initial initial; background-repeat: initial initial; ">varnishes</a>. Some commonly used drying oils include <a href="http://en.wikipedia.org/wiki/Linseed_oil" title="Linseed oil" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">linseed (flax seed) oil</a>, <a href="http://en.wikipedia.org/wiki/Tung_oil" title="Tung oil" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">tung oil</a>, <a href="http://en.wikipedia.org/wiki/Poppyseed_oil" title="Poppyseed oil" style="text-decoration: none; color: rgb(6, 69, 173);
background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">poppy seed oil</a>, <a href="http://en.wikipedia.org/wiki/Perilla_oil" title="Perilla oil" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">perilla oil</a>, and <a href="http://en.wikipedia.org/wiki/Walnut_oil" title="Walnut oil" style="text-decoration: none; color: rgb(6, 69, 173); background-image: none; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: initial initial; background-repeat: initial initial; ">walnut
oil</a>. </span></div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt">and there are lots more details here, including the note that drying oils initially increase in weight significantly (17% for linseed) as they dry, due to absorption of oxygen..</div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt"><br></div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt">It also reminds us that because of polymerization linseed oil is used as a binder/ardener for things like linoleum, wood finishes, putty, etc. so we may want to further consider any "drying" oils for densified fuel applications. "Boiled linseed oil" is the name given to a product that is particularly good for hard coatings - the heat treatment starts the polymerization.</div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt"><br></div><div
style="font-family:bookman old style, new york, times, serif;font-size:12pt">Charlie</div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt"><br></div><div style="font-family:bookman old style, new york, times, serif;font-size:12pt"><br><div style="font-family:arial, helvetica, sans-serif;font-size:10pt"><font size="2" face="Tahoma"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> "ajheggie@gmail.com" <ajheggie@gmail.com><br><b><span style="font-weight: bold;">To:</span></b> pietverhaart@bigpond.com; Discussion of biomass cooking stoves <stoves@lists.bioenergylists.org><br><b><span style="font-weight: bold;">Sent:</span></b> Tue, January 25, 2011 12:03:57 AM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [Stoves] (no subject) [Jatropha cake properties]<br></font><br>On Monday 24 January 2011 23:44:30 Peter verhaart wrote:<br>> If Jatropha oil is a non drying oil (like castor
oil), you are in deep<br>> oil. If Jatropha oil is a drying oil, you might try using a drying<br>> accelerator for paint and/or place the briquettes in an oven.<br><br>Hi Peter<br><br>I don't know whether Jatropha is a drying oil. I believe linseed is and <br>cotton rags allowed to dry with linseed on then heat up and can self <br>ignite, Does anyone know the mechanism for this?<br><br>AJH<br><br>_______________________________________________<br>Stoves mailing list<br><br>to Send a Message to the list, use the email address<br>Stoves mailing list<br><br>to UNSUBSCRIBE or Change your List Settings use the web page<br><a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br><br>for more Biomass Cooking Stoves, News and Information see our web site:<br><a href="http://www.bioenergylists.org/"
target="_blank">http://www.bioenergylists.org/</a><br><a ymailto="mailto:Stoves@lists.bioenergylists.org" href="mailto:Stoves@lists.bioenergylists.org">Stoves@lists.bioenergylists.org</a><br><a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br></div></div><div style="position:fixed"></div> </div><br>
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