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Adding firewood too fast? Cold fire/hearth - Forno Bravo Forum: The Wood-Fired Oven Community

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Adding firewood too fast? Cold fire/hearth

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  • Adding firewood too fast? Cold fire/hearth

    Hello loved ones,
    I may be answering my own question here, but I'd love some input to confirm or at least set me right. I think I am making fires wrong. I seem to be in a hurry to get a large, very hot fire and to get it as fast as I can. So I have been adding wood perhaps a little too enthusiastically. What's happening is that I end up with unburnt wood under the burning wood, so that though the dome may well be hot enough, the hearth does not get as hot as it should and when I rake out coals (for bread) the temperature drops much too rapidly. This is not an insulation issue as I have been able to get the oven pizza hot while maintaining a roaring, beautiful pizza fire and still have decent heat the next day. Heat retention has not been a problem in general. It may be that I don't have a full grasp on how to build an efficient fire and have only been lucky, sporadic.

    So I guess my question has to do with the pace at which one adds wood. Should I be more patient with adding wood? I seem to be defeating myself in my hurry.

    I will say this: Building and maintaining a fire in a WFO is not the same as building and maintaining a fire to drink beer around and roast hot dogs over. So if you got your fire building merit badge in the scouts and feel good about your fire building skills, it may be time to be humbled.

    Thanks all.
    Kim

  • #2
    Re: Adding firewood too fast? Cold fire/hearth

    I don't think fire size is a problem. The size of the materials in your fire may be???

    Ash is a great insulator. Sounds like you have too much small stuff that is burning quickly and settling around the wood on the hearth and both insulating the hearth and keeping air from the wood so it won't burn. I use only a minimal amount of small stuff (on the hearth) to ignite my larger stuff and I always have glowing coals at the hearth.

    In NY you should have pretty good firewood. Make sure it is dry (and it is IMO smart to use the oven to dry wood...)

    Good Luck!
    Jay

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    • #3
      Re: Adding firewood too fast? Cold fire/hearth

      Good morning Jay,
      I don't think material size is an issue. I keep that stuff small. Well, not tiny. Arm diameter or so. But I think you're on the money in saying I "have too much small stuff that is burning quickly and settling around the wood on the hearth and both insulating the hearth and keeping air from the wood so it won't burn." So should I just go a little easier on how soon I add wood? My wood stash is nice and seasoned/dry. No problem there. And yes, we do have plenty of good wood to choose from here in N.Y.

      Last year I tried drying a bunch of wood in the oven but I did it shortly after the oven had been used. I don't know if that had anything to do with it, but the wood got a bit moldy when I retrieved it later. Granted, it was quite a while later. I wondered (and asked here about this then) if too much moisture had permeated the hearth brick somehow and I eventually had spalling on the hearth and I ended up replacing several hearth brick. I really don't know, and so long as all my wood is dry and well seasoned I won't really need to find out.

      Thanks
      Kim

      Comment


      • #4
        Re: Adding firewood too fast? Cold fire/hearth

        My approach is pretty simple. I pretty much loosely fill the oven with wood - mostly wrist diameter and build s small stash of cedar twigs with needles near the front and use some smaller pieces (say finger size) around that for the twigs to ignite, and larger pieces aroudn that. My fire gets big and hot fast. Once it is burning good I do push the fire deeper into the oven to better ignite the wood in the oven. I burn bottom up, not top down...as some do on the web site.

        Couple of strange things about your problem...

        I am going to guess your oven is an igloo and that water is getting into/onto your hearth. Evidence is in the moldy wood. It can't mold if dry and in a dry oven. The spalling also suggests a moist hearth. That could serve to slow the hearth heating and contribute to the unburnt wood. As could top down burning.... I occasionally have water issues on my hearth but never to the point you describe. I am planning to build a "house" around my oven this winter to keep the hearth dryer and better avoid the wet slab issue.

        My oven has a refractory floor so I don't find the water as much of a problem as (I would expect) on bricks.

        I have to suspect you find the unburned wood in ash for if it were open to the fire the wood would burn. You might consider building a smallish fire for fifteen minutes to heat the oven and surface dry it out a bit... then take out the ashes and smallish stuff and load with bigger pieces and restart the fire (or rearrange and reload if you simply shove the larger burning pieces to the side.)

        Good Luck!
        Jay

        Comment


        • #5
          Re: Adding firewood too fast? Cold fire/hearth

          Jay,
          The oven is a Pompeii thing, taken right from the FB directions. I don't think the mold issue is from a moisture leak but from the fact that the wood at that time was not fully dry - I suspect. I also replaced the spalled brick so what's there now is not the same. Also, I've had a number of good fires since. It's just that I may have done so without actually knowing what I was doing. Hit or miss, sort of. I think I will pay more attention next time to having smaller kindling and allowing fires to build before I choke the hell out of them. I too do the bottom up method as I never really figured out why the top down is used. The pizza doesn't seem to know the difference - or care.

          I too am thinking of building a "house" for the oven, but mostly so I can work it under more conditions. It isn't easy planning on a bake and then getting rain. And here (foothills of the Catskill Mtns.) we get a lot of those summer thunder bursts which, even with, say, a 50% chance of rain, will deluge for twenty minutes on a whim and wreak havoc with fire building, bread/pizza baking. No pop-up tent has been up to the task so far.
          Thanks,
          Kim

          Comment


          • #6
            Re: Adding firewood too fast? Cold fire/hearth

            If it is smoking, then there is too much wood. If I do a long burn, I will scoop out some of the ash to clear the hearth, and I always spread the coals around to heat the hearth before I remove (most of) them.
            Attached Files

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            • #7
              Re: Adding firewood too fast? Cold fire/hearth

              No smoke. Just unburnt wood and coals. And I do rake out ash at times. I refer here to the larger, unburnt and relatively colder wood under the flames. As I adjust logs and rearrange the fire as I go along, I tend to find unburnt wood I had thought was long gone.
              Thanks,
              Kim

              Comment


              • #8
                Re: Adding firewood too fast? Cold fire/hearth

                I overcame my skepticism, tried the top down method recently and was very impressed. One of the big advantages was that after lighting the fire, there was nothing else I had to do. The fire heated up the oven wonderfully and pretty much cleared the dome before I had to do anything. Previously it was pretty high maintenance, adding increasingly large pieces of wood until I had a large fire.

                Karl

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                • #9
                  Re: Adding firewood too fast? Cold fire/hearth

                  I have had 40 years of firing cermic brick kilns and I never , fire up without a warm up , .. the same with my ovens , a 1/2 to an hour small warm up fire will help heat the floor and reduce the thermal shock on your refractories,
                  I also use two substantial lengths of wood that I build my fire on , like andirons, allowing the air to get underneath the fire to make more complete combustion .
                  tim

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                  • #10
                    Re: Adding firewood too fast? Cold fire/hearth

                    I learned a few tricks by attending a few WFO workshops, Kneading Conference in Maine and at Stone Turtle Baking School. Basically, if you place wrist diameter pieces of wood, about 12 to 18 inches in length in one layer around the perimeter of the oven and then place a short stack in the center of the oven in tic-tac-toe pattern with three or four pieces on the bottom with kindling you should be able to get the oven up to temperature for pizza with just that amount of wood. When all the wood has ignited move the fire to the location you like best to keep the heat up for continued pizza making. To do breads I load some more wood slowly to allow the heat to soak into the masonry for an extra hour or two. We have good draft up the chimney and we use dry wood each firing. Once we are through for the day or night and all the embers are out we load the oven with wood in the pattern mentioned above and it really dries out from the residual head in the masonry. If lights very easily.

                    Comment


                    • #11
                      Re: Adding firewood too fast? Cold fire/hearth

                      Kim,
                      I have also experienced the same problem that you have described exactly, a couple of times with mine. Both times were when I was keen to get a big fire going in a hurry, overloaded the chamber with fuel and had lots of black, unburnt wood, mostly in the back of the oven. My oven is small and it is easy to overload. What is happening is that too much oven volume is taken up by the wood and also oxygen can't easily get through. This results in a reducing atmosphere ( fuel excess, oxygen starved) and does not produce a hot fire, exactly the opposite of what you are trying to achieve. The remedy is to let your oven take it's time and put in LESS fuel than you think, particularly at early stages. It is far kinder to your refractory materials to heat slowly anyway, so relax and open another beer and start your fire earlier.
                      Kindled with zeal and fired with passion.

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