I think that the final heating to the point of ignition comes not from bacterial activity but from the fact that anytime you put fuel molecules and oxygen molecules together a few of them will combine chemically and release heat. Whether you consider this burning goes back to the definition of fire. I don't know the formal definition but my own personal definition is that fire is a self perpetuating exothermic reaction that builds up in temperature and is limited by the availability of either fuel or oxygen. By the time this happens stuff is glowing red hot (flames). We are used to viewing objects as conglomerates of unbelievably large numbers of molecules. There is the posibility that one of the atoms that make up your left little toe is at this moment on the far side of mars but you don't really notice that it is missing. The probability that all of your toes atoms should be AWOL all at the same time is infinitely remote, therefore you can be excused for believing that your toe can't be anywhere that you didn't put it, even though parts of it literally are somewhere else sometimes. Similarly, temperature of an object is the average of the temperature of all the atoms that make it up. Some of your toe atoms are at absolute zero. Some are at 10,000 degrees. The average is 98.6 degrees. Now, if you create a nice warm stable environment with just the right ratio of fuel to air, some fuel/air couples will "get it on". They give off heat. If the insulation is good, the temperature rises. If the insulation were really really good, all that is necessary is time for the temperature to slowly rise, even without the effect of increased temperature causing an increased rate of chemical reactions. What I am saying so far is that the chemical reactions that occur in fire can happen at almost any temperature but we don't call it fire until we get the increasing chain reaction where more chemical reaction causes more heat causes more chemical reaction, etc, until the only thing holding things back is a shortage of one of the reactants. Almost always stuff is so hot by then that it is glowing red hot (fire). I believe that haystacks can start on fire not so much because of 170 degree bacterial activity being the ignition point but because a large enough composting haystack creates a wide enough range of microclimates that one of them will have just the right combination of fuel (methane, cellulose, hydrogen, ethanol, etc) and oxygen, combined with really good insulation and a good 170 degree head start. I read an interesting thread on the flamability of sprayed on urethane insulation. If you take a chunk of it and put a flame to it it will smoulder and go out but there have been some horrific fires in large metal storage buildings coated with the stuff inside precisely because it is such a good insulator. The heat can't get out. Eventually, by which I mean within a minute or two, temperatures shoot up to the point where anything capable of burning would burn, and so the insulation does. So would wet compost only compost has a high thermal mass and a more modest R-value so it takes longer and the ideal conditions are met less frequently. The point is to embrace modern physics and the idea that for atoms you can't nail down such mundane physical properties as where they are and how hot they are, only the probabilities of such. These probabilities often have peaks that might lead you to draw sweeping conclusions such as that your nostril hairs couldn't be on fire, while in reality every so often a hair molecule does in fact combine with oxygen and give off heat. It couldn't be otherwise. In a large compost pile, which is almost infinitely larger and better insulated than your nose, there will be pockets that come perilously close to meeting all the requirements for the heat to build up to the point that these chemical reactions meet the criteria for being called fire.

pnb - all of the work I've seen on extracting heat from compost process has been done with static piles, with one exception (some crafty Brits). The problem with a static compost pile as a thermal energy source is that it is an out-of-control process, meaning there is no control. That presents a number of challenges to make the capital investment worthwhile. Composting for a thermal energy source will need to be much more precise than what we tend to practice around our gardens. The composition of the mix, including moisture, should be controlled with a measure of accuracy generally unseen in gardening. Capturing and using the heat generated from the decomposition of organic materials for controlled use is no longer just getting decomposed materials - those are down on the list as waste materials. Then there is pile size, geometry, etc.. It's not a simple list. I believe the engineering approach would be to oversize the pile to assure that, within a reasonable range of expected heat generating capacity, it would more than meet the demand, then add a means of exhausting the excess heat as waste. There are a number of ways to exhaust the excess heat. The trick is being able to control it. There has been a lot of work done with heating greenhouses, which is less demanding than residential space heating. A pretty good assessment is available in an undergraduate thesis from the University of Waterloo in Canada (good school!). If it were me, I'd start small and try to work out the bugs and control issues with something like hot water.

SInce you were all so nice about my initial question, I have a few follow-ups: Gloves: do you use decent ones, rinse and dry them, or use cheap disposables and discard every time? And can they be dried and discarded in the garbage? If you take a solvent out of its container to put in a smaller one, what do you use? Glass and re-use it? How do you dispose of it? I've been using a mix of turp and linseed oil to freshen up some furniture. I put it in a cottage cheese container and now don't know if it's safe to keep it in there. Sorry if these questions seem dumb/basic. I'm super-paranoid about fires because we had a housefire once, and I want to do the right thing in terms of environmental safety.

Good luck buying zinc points! But you can make some for yourself if you have the patience. I'm still painstakingly hammering my salvaged ones flat. I have tried some of the Allback products - they sound very appealing. But the whole organic boiled linseed oil won't support mildew assertion is a crock in my experience at my northern NY home. I have tested it (on my privy) following prep and application instructions very, very, carefully. I get mildew on it, the same as on nearby surfaces untreated with Allback Swedish Organic Boiled linseed oil paint. When I complained I was told it was because of the wet weather that year (not occuring during painting or curing, but months afterward.) I tried again another year, same results, different excuse from the company. I've seen some reports that they are getting pretty dodgy on that claim, lately. I'm not saying the paint doesn't work, or achieve a truly different looking surface that's quite attractive. It does all that. But it still mildews if conditions are right. I haven't tried the putty. Why not try Sarco putty? I use it and find it excellent. Try John Leeke's website for more info and data regarding Sarco and Allback. Even if the guy you quoted above is a shill for Allback, he's right about one thing: Dap-33 is awful! But some of his claims, like that 20% of all housefires in the US being caused by heat guns don't sound very likely. He may also not be a shill, just a sloppy and less-knowledgeable-than-he-seems writer. The organic boiled linseed oil liquid soap is very nice to use; smells great, cleans pretty well. I keep it on hand for occasional household uses where regular detergent-based soaps would be inappropriate. It's expensive, though. HTH, L Here is a link that might be useful: John Leeke's extremely useful website on windows