Can Cardboard with Stain or Poly Drips Catch Fire on Its Own?

While it’s theoretically possible for cardboard to ignite, it mostly happens with balled-up oily rags. Those can heat up because of the reaction during drying. Just hanging your rags outside or keeping them wet can prevent any risks. I had a close call once when I left rags bunched up after a stain job and came back to hot, smoldering rags in a bag! So just keep everything out in the open, and you'll be fine.

You're in the clear! Only certain oils, like linseed or tung, can heat up enough in enclosed spaces to pose a danger. Flat cardboard isn't going to spontaneously burst into flames unless it gets really hot, and that's not likely with how you're set up. Just keep everything ventilated, and don't worry too much!

Oils can spontaneously combust in things like rags because of heat generated during their curing process. When you use oil that hardens, it can be a fire risk if they're crumpled up, as the heat accumulates instead of dissipating. Flat cardboard with stain drips will let any heat escape into the air, so it’s not a major fire hazard. It's always best to be cautious, but those drips on cardboard are much less risky than wadded-up rags!