Our thoughts are definitely with the owners of Andy Lakes Woodworks in Glyndon, Minn., after three log sheds and a shop building burned down Saturday (May 6, 2017). Officials say the fire started when finishing chemicals spontaneously combusted. For more information, visit http://kfgo.com/news/articles/2017/may/07/fire-destroys-glyndon-woodcarving-business/.
This is really a wakeup call for carvers. Any finish containing boiled linseed oil (and many other oil finishes) can spontaneously combust. When these kinds of finishes cure, they produce heat. On a project, this isn’t an issue because the finish is thin and open to the air, so the heat can dissipate. But, if you crumple up oil finish soaked rags, the concentration of finish is higher and more concentrated, and the rags are very flammable, so these rags are a huge fire risk.
Personally, I was applying an oil finish to some ornaments a few years ago, and used rags to wipe off the excess finish. I was in a hurry, so I left the rags outside crumpled up. It was Christmas time (which is pretty cold in Central Pennsylvania), so I thought it would be safe. I came out the next morning to find a pile of fine ash and melted snow where the rags used to be.
If you use any oil finishes, take care of your rags properly. Some folks store them in a bucket of water and a grease-cutting dish soap until it’s time to throw them away. Other people flatten the rags and let them dry thoroughly or hang them to dry. This is safe because the rags are spread out so the heat dissipates. Other people put the rags in a fire-proof container or take them outside to a burn barrel immediately after use.