Question: I have some good news. I was able to achieve a couple of very long burns with wood in my potbelly. I was even able to get burn times around 12 hours keeping the greenhouse at 50 degrees which is my target temperature. Unfortunately, I am using too much wood and as a result, I just went out and bought 4 buckets of coal. I've read the coal tips document extensively, but I still have a few questions. Since I will be burning both coal and wood, do I have to worry about the fly ash catching the creosote in the chimney on fire, or is the fly ash cool enough that it wouldn't? For an average overnight burn, how much coal should I use with the air and damper shut completely? Is it ok to leave a small layer of creosote on the inside of the chimney to protect it from the SO2 in the coal smoke? Thanks for all your help so far it really made a difference. Answer: No worry about catching creosote with the coal, etc. The problem is really that they should not be mixed in the fire or the wood ash may choke the coal. Here's the way to do it. Wait until the wood is at a point where it is mostly a bed of hot embers. Shovel a layer (maybe 1" ) of coal on top of this and then open the air control and damper fully. When this is caught, add at least 5-8" of more coal on top and adjust the dampers. It will take some fiddling to find the right damper settings, but once you do you'll be able to throw new wood or coal onto the fire in the morning and have it burn nicely.