it's an art and a science. I really thought I had mastered the art side of things, but the past few days I've really struggled to keep a fire going without resorting to cracking open the ash door for fresh air. it was really frustrating. so today I took the back heat shield of the stove off and sure enough, the chain connected to the internal damper had fallen off. I'm not entirely sure what that chain moves inside the bottom of the stove (there's a separate chain for the thermostat flapper), but I repaired it and today's fire is roasty-toasty so it was clearly something important. part art, part science, and this time it was a science (engineering) failure.