Burning the Creosote

I’ve (again) learned something new, at the ripe old age of 33. I never knew what creosote was, I mean, I had heard of it, but not sure I’ve ever seen it, much less have had to deal with it ever at any time. Now, after a long nights burn in which I packed the furnace to the gills – just to see if it would burn ALL of it overnight – I noticed a large build up of bubbly creosote.

Creosote or pitch oil is the name used for a variety of products that include wood creosote and coal tar creosote. The word is also used to describe the black oily accretion that builds up inside of chimney flues as a result of incomplete burning of wood or coal. Commercially, wood creosote is created by high temperature treatment of beech and other woods, or from the resin of the creosote bush.


Burning wood and fossil fuels at low temperature causes incomplete combustion of the oils in the wood, which are off-gassed as volatiles in the smoke. As the smoke rises through the chimney it cools, causing water, carbon, and volatiles to condense on the interior surfaces of the chimney flue. This leaves a black oily residue referred to as “creosote”, which is similar in composition to the commercial products by the same name, but with a higher content of carbon black.

So, thats your word for the day and something you’d only have to worry about if you ever buy a house with a wood furnace. Well ok, I guess maybe chimneys can get dirty burning oil and stuff too but I’ve never really seen anyone worry about chimneys for oil furnaces? I never recall Dad worrying about the chimney for that…

Anywho, this is part of my project for this coming weekend. To clean out the chimney and start to learn how often our chimney will need cleaning. Every couple weeks? Every month? A good friend Vince does his every month. I’m burning wet wood methinks which is not ideal at all so i’ll have to keep an eye on it.

In other news, talking about this means that I was able to finish my boiler! Only one small, or even tiny leak which I’m not worried about for the moment on one of my couplers. THe system is otherwise working well. And let it be known, i’m trying with a brand new electric hot water tank from which the insulation has not been removed. I’ll let y’all know how that goes 🙂

Oh, and as for the title of this post, I have my damper full open right now, they suggest that to get a nice hot fire that will burn out some of the creosote and help limit build up… there ya go…

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2 thoughts on “Burning the Creosote

  1. Does your wood stove have thermometer on the chimney pipe? We got one a few years back from Lehman’s Non-Electric and it tells you if you are in the optimum burning range. It just magnets onto the chimney pipe. The lower temperatures indicate creosote build-up, the mid range is best, and the upper range will burn what creosote is hanging about in your chimney. 🙂 Not necessarily recommended, but a little chimney fire basically means you don’t have to clean the chimney for another month or two…

  2. welp, its a full out furnace, so it has an auto damper which shuts it down at night if its too hot. so it ends up creating more then maybe someone with a wood stove would. But, they do recommend running it full blast for 2 hours once a week to burn out the chimney just as you say. so likely I’ll be doing that to make up for all the nightly lower temps.

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