Is There a Tradeoff Between Burn Time and Creosote Formation?

I burn hot enough to keep the glass clean.
That is my thermostat and it gives me a big range.

The first few hours of the burn are when most of the creosote thingys are off gassing from the splits. As the fire burns down to the coaling stage there is little creosote formation and the temps will drop. What are your pipe temps? They will give you a better idea of what's going up your flue.

DanCorcoran said:

Okay, I've used my stove a few times now and have noticed that when I keep the stove in the "good operating" zone on my Condar stovetop thermometer, I have the air control open more and add wood "more" often. Well, sure . . . you've got plenty of air flowing and a good fire going, but a good portion of this heat is also going up the chimney and if you keep the air control open all the way you will not get the benefit of secondary combustion . . . and as noted you will be adding wood more often. This is normal . . . and in fact you want your air control open when you're first starting the fire. When I go for a long, overnight burn, I shut the air down somewhat and get a much longer burn. The longer burn is at the expense of temperature though. After the stove is burning more slowly, with less air, the temperature is in the "creosote" zone. If I open the air to get the temperature back up, the stove doesn't burn nearly as long. Well, if done correctly . . . and if the wood is good . . . you should be able to get the benefit of a longer burn, clean burn and your temps will continue to stay up in the "zone" for a long time . . . well after you've fallen asleep.

Also, no matter where I have the air control, if I need to let the fire go out, as the wood is being consumed and no more is added, the temperature goes down below the ideal operating zone. (This sounds like a no-brainer...how could it not go down: stay high until the last minute and then instantly drop to room temperature?) As mentioned most of the "bad stuff" is burned off in the first part of the burn . . . if you're burning correctly the secondary burning should be burning off the bad stuff in the first part of the burn . . . by the time the temps start dropping to below the "Goldilocks Zone" as marked on the thermometer you should be OK since as you noted it's not an all-or-nothing proposition -- it's the normal progression of the fire as it dies out.

Is it possible to have a 3-4-5-6 hour burn with the air input lowered, but still keep the stove in the "good operating" zone? Well yes and no . . . the thermometer may read that you are burning too cooly after 3-6 hours of burning . . . but if you've run your stove correctly you should be fine as the bad stuff was burned off early in the burning process. Now for the first hour+ you should however have high enough temps and be in the Goldilocks Zone without any issues. Or as the wood is consumed on a long burn, is the temperature by definition going to be lower than otherwise, and is this probably going to be in the creosote zone?

If all of you long-time overnight burners are able to keep an all-nighter going with the temperature in the "good" zone, then I'll blame my wood.

Click to expand...

A few random thoughts . . .

-- Take what the thermometers say with a grain of salt . . . once they reach X degrees and are in the Goldilocks Zone don't assume you're OK -- most folks know not to treat the numbers and readings as figures set in stone, but rather use the thermometer as a rough guide . . . watch the fire as this will tell you almost as much as the thermometer. A free burning fire means your air may be open too much. A fire that is choked off and barely burning and the firebox is full of smoke may mean you need to have more air. A fire that is burning with secondary combustion (i.e. the Northern Lights, Bowels of Hell, Propane BBQ jets) is good . . . very good.

-- I find that with my stove I can get the temps on my thermometers up and in the zone within no time . . . but if I try to shut the air too much or too soon . . . especially on that first cold start . . . the fire will often be suffocated and the temps will plummet. Generally, this isn't such a problem with an established fire and when I'm doing a reload.

-- It seems to me that when you start shutting the air (which is desired for longer burns and secondary burns) there are a few variables that will influence on how soon you can do this . . . and if the results will be good or not. Perhaps the most important factor is the wood . . . how well seasoned it is. Semi-seasoned = it will take more time to completely drive the moisture from the wood and shutting down the air too soon will result in smoke, dropping temps. Fully seasoned = wood burning nirvana. Another factor seems to be time . . . I suspect that the reason my first fire in a cold start never is that spectacular and seems to take a long time to get really going (i.e. the ability to reach secondary burning happiness) is that it takes time to heat up the air and thermal mass to the point where those higher temps can more easily sustain the secondary burn. Generally, the second reload after a cold start is a lot more impressive as it takes less time to achieve secondary burns and the temps really seem to pore out of the stove on that reload.

-- On a cold start . . . heck I sometimes do this on a reload . . . bring the temps up to the Goldilocks Zone . . . even let them climb a bit higher than the minimum . . . and then start closing the air control . . . a quarter mark at a time . . . waiting 5-10 minutes every time you do so . . . if the fire does well after that time, close it down another quarter mark until the air control is either completely shut or open just a bit to a quarter open . . . if the fire however starts to splutter and smoke up as you turn it down, leave it there at that point for a few more minutes before again attempting to turn down the air a quarter mark. It takes time . . . but this has worked for me.

Keep in mind that those "zones" on magnetic thermometers are almost always, if not always, designed to show the flue gas temp ranges as measured 18" high on a single wall pipe - not the operating range for a stove top. Your stove's manufacturer will (or should) specify the appropriate temperature ranges for the stove. For example, my Endeavor's manual says anything over 800F is considered an overfire condition.

My stove top routinely "cruises" at 600-650F during the "meat" of the burn phase. The only way I can get it lower than that, really, is to shut down the primary air all the way and let the fire smolder. But that creates a huge mess on the glass and in the flue, I presume.

Also bear in mind that the charcoaling stage is naturally clean burning. You're not creating anything to dirty up your flue during this stage.

I would focus less on the ranges specified on the thermometer and more on: 1.) the stove's normal/recommended operating range as specified by the manufacturer and 2.) maintaining active, secondary combustion until you reach the charcoaling stage.

Wow Dan, you've got some good answers above! I hope it helps.


My first thoughts are usually with the fuel. Good fuel = good results. Bad fuel = bad results. To carry further, moderately good fuel can give some good results or bad results depending upon the installation and the guy running the stove.

As for us, over the few years we've burned (look at my signature line) we have come to the conclusion many moons ago that good dry wood is an absolute necessity. Yes, we have had a few years when we burned less than ideal wood but also suffered the consequences. While it is true that we did not freeze, we did stay warm but burned a lot more wood and cleaned our chimney a lot more than we do now. With good dry wood, we clean the chimney annually or semi-annually as needed. We burn a lot less wood and get a lot more heat from the wood. It is not difficult to get a fire going either with good dry wood. What that means is that we like to burn wood that has been cut, split and stacked for a minimum of 2-3 years or more. The last several years we've burned wood that was in the 6-7 year old range.

Also with our newer stove, we burn about 3 cords of wood per year where it used to take us 6 or more cords per year on average.