Spontaneous combustion, or self-ignition, has been a topic that followed me over the years. The basic concept is that an exothermic decomposition or oxydation process creates more heat than the heat losses in the surrounding area. 

Linseed oil, paint filters and a deer target

My first encounter with the topic was as an undergraduate student at the University of Maryland when Prof. Jose Torero asked me to prepare a self-ignition demonstration for a fire investigation course for the Bureau of Alcohol, Tobacco, and Firearms (ATF).  Similarly to what is shown in the photos below, I used cotton rags and linseed oil for the demonstration. With some practice, supported by careful measurements and observations, we created a box that burst into flames in the parking lot while Jose was explaining some details. Success!