An awful lot of commonly-used solvents are known to self-combust in suitable conditions. Prevention is fairly easy - spread the cloth or hang it in a well-ventilated space until dry.

I spent a year as a security guard at a cardboard box factory in London in the late 50s. Most boxes were printed, and a lot of solvents were used for cleaning the machines. Our main duty was patrolling the factory hourly through the night looking out for incipient fires. In the year, I dealt with about 20, any of which could have destroyed the factory if left for a few hours.

There was a another fire risk. The detergent boxes were printed in 4 colours on fairly coarse cardboard. Printing was done on a continuous roll of board running at high speed through 4 printing rolls. Unfortunately, ink technology then was not able to get the one colour to dry before the next colour was printed. The solution was obvious - play a naked gas flame over the cardboard as it came out of each roll. As long as everything kept moving, the risk of fire was low. If the cardboard broke, the trailing half usually caught fire before the auto cutout shut off the gas. Brightened up the night for a bored security guard!

Phil