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Black Shiny tar

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Treemoss, Nov 6, 2013.

  1. Treemoss

    Treemoss Member

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    When I took my chimney cap off today I noticed on the inside was some shiny black tar. it was a little sticky in some areas. There was also black on the inside of the pipe but not sticky. I've only had about 4 weeks total of burning wood through the new pipe. I know I have good wood I've had it burning over a month the wood burns up very fast. I took the bottom tee cap off and the pipe inside have a light gray dusting on it of dry nothingness. Why does the top cap have dark sticky film. should this already be this way. Should I be concerned. Or is this because the top of the chimney is the coldest and it forms there first. Will this start to travel down into the pipe from the cap or just stay near the top only.

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  2. begreen

    begreen Mooderator Staff Member

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    At this time of year before 24/7 hot burning this is not uncommon. The flue temps at the top of the chimney are the coolest. Once they are below 250F creosote will start to condense. A little shiny sote on the underside of the cap is ok. If you start seeing glaze in the pipe you may need to run the fire a bit hotter. Plan on cleaning the chimney mid-winter and see how things are going. The wood may be a little damper than expected. Wood with 22% moisture is probably going to burn fine, but will cool the flue gases down a bit.
  3. Jags

    Jags Moderate Moderator Staff Member

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    I "thin" coating has very little fuel in it (think aluminum foil thin). It is good to be cautious and as BG stated - take another good look at it in a month or so. If you start to see any more build up - get a brush run through it.
    What kind of temps are your running the stove/stack?
  4. Treemoss

    Treemoss Member

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    I think I will check it out in a month thanks guys. I just can't believe that there is tar already 4 weeks. I run the stove top between 400 and 550 then just let the coals break down then it runs at 200 350 for hours. 1 cold night I did have it at 650. Even if I run it at 650 will that be enough to burn up the tar at cap. Or do I have to clean it before it is worse.
  5. begreen

    begreen Mooderator Staff Member

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    When it gets in the 20s and below outside you will be running the stove at 650F most of the time. Don't worry about the cap, it's the flue you want to watch. If you find a thin layer of brownish grey fluffy powder in the upper flue you are burning well.
    HDRock likes this.
  6. hobbes105

    hobbes105 New Member

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    I just did the same thing yesterday. I'm new to wood burning and I have a new stove installation and chimney. I just finished installing it about a month ago. Took my cap off to check and make sure that everything looks ok. After burning about 4 weeks of poplar and oak, mine looks exactly like you are describing - black shinny stuff in the cap, but the rest of the chimney is mostly clean with some grey / black powdery deposits. I attached a few pics. I think this is normal.

    Attached Files:

  7. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Hobbes, you are doing just fine. One little note on your screen. That is what will plug first. If it is possible to reach that screen from the outside with the poles you use for cleaning the chimney, many times you can just lightly tap the screen and the junk will just fall off. This will save you having to go up top with a wire brush so often.

    Treemoss, do not think it strange to find this in 4 weeks. Many have found this in as little as a week. Your wood also may not be as dry as you think. Burning dry wood has many advantages and keeping the chimney and cap clean is just part of it. We put up a new chimney and cap in 2007. The chimney has been cleaned once and the cap has been untouched. This is thanks to very dry wood and a super clean burning stove.
    tfdchief likes this.
  8. hobbes105

    hobbes105 New Member

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    Thanks, My cap is really easy to get to - just need a 6 foot ladder to hop up onto the roof. I'll be sure to keep that screen clean.
    Backwoods Savage likes this.
  9. HotCoals

    HotCoals Minister of Fire

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    Even if your wood is very dry..water is a by-product of burning wood.
    The top of your stack will be even cooler once the real cold gets here. That said you will prolly have a hotter fire because of the colder temps.
    Insulated pipe?
    stoveguy2esw likes this.
  10. hobbes105

    hobbes105 New Member

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    I do have insulated pipe - double wall Dura Vent stove pipe and 5' of triple wall Dura Plus chimney.
  11. HotCoals

    HotCoals Minister of Fire

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    I would check joints everywhere I could..any connection I would check over.
    I burn low and slow and get some flaky crap at the cap..but nothing hard and shiny.
    Running the stove really hot will not clean that area off once it's there.
    Backwoods Savage likes this.
  12. hobbes105

    hobbes105 New Member

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    Yeah, I don't really expect a hot fire to clean that. It's not as hot at the chimney cap as I imagined it would be - the outer layer of the insulated pipe at the cap is cool to the touch with a probe temp of about 500 down by the stove (I was up there a few days ago cleaning the gutters while the stove was burning). I cleaned all that crap out of the cap yesterday after I took the pics. I'll keep an eye on the joints until I get to know this stove and chimney better. There did seem to be a little more of a build up of stuff at the joints when I looked down the chimney with a flashlight, but nothing like what the cap had.

    I've been trying to keep the flue temps up, but sometimes it just gets too hot in the house. It was 27 degrees the other night and the house was at 82 degrees with a window open and fans going. We have a small ranch house and this Dutchwest stove is probably a larger stove than we needed, but I got it for free from a friend.
  13. HotCoals

    HotCoals Minister of Fire

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    How tall is the chimney?
    Decent draft?
    Do you see much smoke after the fire is well established?
  14. hobbes105

    hobbes105 New Member

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    Chimney is 16' tall.
    Draft seems fine, don't have any problems with dampening down & closing down the air.
    Once the temp is up in the box & the flue there's no smoke.
  15. Nick Mystic

    Nick Mystic Minister of Fire

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    Early in the season like this you have to build more fires from a cold start. I think that is where the worst of the tarry stuff in the caps comes from. My big Jotul F600 has to get a decent bed of hot coals before it really starts to burn efficiently. I notice a fair amount of smoke coming out of my stack during those start up periods. It doesn't matter if I burn a hot fire to get things lit off in the stove I still can't get any sustained secondaries until the entire stove gets good and hot.
  16. Treemoss

    Treemoss Member

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    My cap is about 20ft from the top of the stove. My cap is not as bad as yours Hobbes but I do have a little black tar. Should I try to clean it or leave it, and if so what do I clean it with. I see tho's powder gimmicks treatments that say they dry up the tar to power. But does that really work? Maybe I should just go up top and scrub it with my brush before it is thicker and harder to get off. Will wiping it off with a gas soaked rag work well. I know that works well with roofing tar.
  17. hobbes105

    hobbes105 New Member

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    Since I was already up there I just cleaned it with a wire brush. It came off very easily. I don't thing you'll need anything other than a brush.

    I have some Rutland creosote remover, but haven't used it. I figured that I would use it before I sweep the chimney to make cleaning it easier after a season of burning.
  18. Jags

    Jags Moderate Moderator Staff Member

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    THIS is the intent of that stuff. It does not replace a cleaning, it just chemically dries up the goop making it easier to clean.
  19. Treemoss

    Treemoss Member

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    so it does work, I think I will just scrub it like you hob. I figure I will clean the chimney pipe after every cord just to see how it is. It only takes me 20 min.
  20. Treemoss

    Treemoss Member

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    Can any of you guys direct me to a good wood moisture meter to buy. I am getting another cord of wood delivered tomorrow. I would like to see how the moisture content is.
  21. stoveguy2esw

    stoveguy2esw Minister of Fire

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    biggest thing about creosote is stack temps, in actuality 211F is the point where it forms due to moisture changing from a gas to a liquid (water vapor) it can form even with well seasoned wood provided the stack temps have dropped too far.

    remember, small loads in the shoulder season should not be burned slowly in an EPA stove. make sure you get the stack heated properly and burn brisk fires if possible. the lack of thermal energy expelled by a modern stove can cause creosote even with a complete burn as the smaller load produces less waste heat which the flue needs to hold above the condensation zone. also a short load will not produce as much of a coal bed which helps hold heat in the flue as teh fire dies out allowing cooling at a faster rate in the flue.

    simply put, shoulder burning should be short but hot fires allowing the fuel to burn away rapidly and let the stove's trapped radiant heat supply the smaller needed heat as it cools, a long slow burn with a short load is an easy way to make creosote
    HDRock likes this.
  22. HotCoals

    HotCoals Minister of Fire

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    I concur and I would add that these stoves are designed to get the fire box up to temps for a more complete combustion.
    That's why some have double wall,fire bricks and what not to get the box temp up 1000 degrees f or more. Not to mention secondary tubes or catalytic converters to clean up the pollution.
    But even with all that moisture will reach the flue.
  23. HDRock

    HDRock Minister of Fire

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    I think It's the same for a smoke dragon or an epa , burn it hot, get the flue hot
    Hay if you need to open a window, or take your cloths off , so be it
  24. HDRock

    HDRock Minister of Fire

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  25. Treemoss

    Treemoss Member

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    Thanks for the info, I will be getting one this week.

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