Strange Black Stuff in Chimney

[jsnitzer]

Got a Lopi brand fireplace insert last year and used it all winter. This year I cleaned the stainless steel chimney liner with one of those brushes from Lowes. Instead of soot, I knocked loose a small bucketful of black stuff from the size of sand up to 2" rocks. The 'rocks' are very porous - look like a sponge and shiny black.

Is that normal? Dangerous? Am I doing something wrong with the way I am using the insert?

[beenthere]

That is called creosote, and it comes from the unburned gases condensing in the chimney as they cool.
Several things contribute to the creosote, and sometimes it is a catch-22 to hope to eliminate all of them.

Wet wood contributes, a cold chimney contributes, stove dampened down contributes, too much wood in the stove contributes, species of wood contributes.

There are other conditions too, but read in your manual about creosote, and see if you can work to eliminate or minimize its formation in the chimney. The problem with creosote forming is it can catch fire and cause a chimney fire that can create too much heat in the chimney. The creosote can also block off the chimney, causing poorer draft conditions which leads to more creosote forming, and may eventually block the chimney altogether.

[Pat]

Every so often 2nd or third fire (but oppinions vary widely) you need to throtle up and really heat up the stack long enough to clear the deposits. A big danger is to let so much accumulate that if it does start a "chimney fire" it can cause damage or start combustibles in the chimney construction on fire.

I wonder if anyone ever saved it, disolved it in an appropriate solvent and soaked fence posts or whatever in it?

Patrick

[jyoutz]

I too have a Lopi (past 9 years -best insert stove I've ever owned). Every night I start the fire with resinous pine firewood. I let the fire burn for 2 - 3 hours with full airflow. The fire burns really hot, removing deposits from the chimney. Then I add a longer burning, less resinous wood for overnight and damper the airflow down almost all the way. Using this method, I've never had a cresote build-up problem. I sweep the pipe annually, but all that I ever see deposited is just soot, no large creosote chunks. Creosote build-up is an indicator of either: poor chimney draft, burning unseasoned wood, burning seasoned wood at too low a temperature without sufficient hot fires to keep the chimney cleaned, or a combination of these things.

[I_am_the_walrus]

Nothing like a good old fashioned chimney fire.....that will clean the creosote out.....also make you go clean your shorts out wow.....been there done that.... [img]/forums/images/icons/crazy.gif[/img]

[jsnitzer]

Thanks all! Guess I have been doing a couple of things wrong, like using green wood (this year its dry!) and most of all, I have just been stuffing the firebox full a couple of times a day.

Now I have started to just throw on a couple of pieces of wood at a time, hoping the flames will burn the creosote in the firebox so it won't have a chance to condense in the chimney. Also will try a hot fire every once in a while.

Also did a search on TBN - a fireman mentioned that an old guy used to let the creosote just build up until it caught on fire, so he would get a free chimney cleaning. Happened about once a year until the fire guys finally decided to put it out with water! [img]/forums/images/icons/smile.gif[/img]