Black Smoke

[Sweet Shady Lane]

Ok ,Guys and Gals
I'll give you the facts as i know them

1 I have a Half pint set up and it works great
2 My fire wood is hardwood mostly small pieces but some bigger, dry and stored inside for a year
3 Has a 6 inch smoke stack that is from top of the fire box to the top cap is 12 feet long

My question is, why is it that when i add firewood to the fire box that i get black smoke ( like i'm burning tires black smoke ) it only lasts a few minutes , i always feel like the neighbors are going to call the fire department on me. Any ideas on how to stop it from happening.

[Buffalo Plaid]

I would say too much fuel trying to ignite at once uses up all of the oxygen creating a rich condition. You can see the same thing happen when you throw a Christmas tree on a bonfire. Adding some air should clear up the smoke

[SeanD]

Completely normal for us wood burners. It's just the cold air from the door open and the cold wood cooling the combustion chamber and reducing the cleanliness/efficiency of your burn. If you were seeing it the whole time between firings, it would be an issue, but you say it burns off which means your firebox is getting the air it needs and back up to temp. You can experiment with your efficiency by making your firings as faster, cutting your wood smaller, mixing the sizes of your wood pieces, and spacing the wood differently (I prefer the log cabin).

[ecolbeck]

Completely normal for us wood burners. It's just the cold air from the door open and the cold wood cooling the combustion chamber and reducing the cleanliness/efficiency of your burn. If you were seeing it the whole time between firings, it would be an issue, but you say it burns off which means your firebox is getting the air it needs and back up to temp. You can experiment with your efficiency by making your firings as faster, cutting your wood smaller, mixing the sizes of your wood pieces, and spacing the wood differently (I prefer the log cabin).

I agree with this. The only detail I would add is to try loading smaller amounts of wood more frequently. A probe style stack thermometer has been a very useful tool to help me time my firings and keep maximum heat on the pans at all times.

[darkmachine]

I noticed a huge difference when i went from a large firebox under a 6x6 flat pan, to a 2x6. The big fire was smokeless once it was up to temperature, nothing but heat waves out of the chimney. On my 2x6 if i add more than about 20% of the firebox's volume in a firing i get smoke. a few times I had it really chugging along (my stack was cherry red) it didn't smoke when we fed it. My thought is it has to have the right mix of fuel and air to completely combust the gasses the wood is giving off. It's fun to experiment!

[Swingpure]

This thread makes me wonder if I should have split my wood even smaller. I split 3 face cords just for the evaporator, and split them smaller than I would for my fireplace insert, but maybe not small enough. I will have to supplement that wood with, more season wood, from my fireplace wood pile, but they are even larger.

The wood in the pictures attached, are they small enough?

https://share.icloud.com/photos/0b1Vt3haHN1NsAAVUtfOcJf-A

https://share.icloud.com/photos/0d6b3KnNHCKOeD7f9ewvHO_hQ

https://share.icloud.com/photos/074durKHjgqJ9WY1LVV7dmzBw

[ecolbeck]

Wrist sized splits is the rule of thumb that is frequently repeated on these forums.

[buckeye gold]

You can add a blower and it will make a big difference in maintaining your heat and boil efficiency. Simplest would be to add air under the fire or grate. will help with that smoke problem and make a better boil. You don't need anything fancy, even a leaf blower will work or a shop vac on exhaust.

[therealtreehugger]

Once my evaporator gets going good, I religiously feed it every 10 minutes. Pile the wood next to the door, get the heavy gloves on, and go - openthedoorshovethewoodinclosethedoor - as fast as you can. I end up not putting a whole lot in at once, the idea is to keep it steady. And, split it small, like ecolbeck said, wrist size.

Swingpure - It's a little hard to say from your pics because there isn't really a great scale, but I'm going to say it's not small enough. You can always mix it in with other smaller stuff though. Any wood is better than no wood - as long as it is dry!

Another thought on the black smoke - I would get black smoke when I burned damp wood, but also, last year I was trying to use up old wood, that was starting to turn punky. That gave off a lot of black smoke.

[eustis22]

2 My fire wood is hardwood mostly small pieces but some bigger, dry and stored inside for a year

Yeah, going forward burn pine, not hardwood. hardwood a) burns slower, and 2) leaves coals, which makes cooldown after stopping firing for the night problemmatical as coals will boil for a while after you're ready to call it a night. Pine burns hot, fast, and leaves no coals. You will fire more often but shutdown will come earlier.

[buckeye gold]

I use all hardwood. You just learn the shutdown process and how much sap to stop firing at. More important is dry. Type does matter as Eustis said some kinds burn faster and hotter, but it all needs to be dry

[darkmachine]

With forced air if we miss a firing (we burn oak sawmill slab, wrist size) it will burn way down, miss 2, and almost nothing is left. Almost as good as shutting down when using oil, lol

[Sugar Bear]

Adding new firewood to a fire, regardless of its moisture content, always results in the following for at least a period of time, incomplete combustion which results in smoke, gray or black coming off the wood.

Once a certain temperature is reached in the immediate air in and surrounding a fire then complete combustion takes place. I.E. the wood and the smoke coming off the wood all burn or combust.

The factors that determine how quickly, the temperature in and surrounding a fire, which is necessary for complete combustion to take place are dependent on many, many, many, things.

The two MOST important factors for wood fires to obtain complete combustion are the following.

1) Enclosure
2) Oxygen Supply

Wet wood in a proper enclosure with a proper oxygen supply will achieve full combustion.

Dry wood in no enclosure and open to atmosphere will never achieve full combustion.

This summer we had fires on the Pacific Northwest Rim. The terrain/fuel was bone dry. Yet smoke from those fires traveled 2000 miles up and across the continent and down the Canadian Shield and across the Tug Hill Plateau and on down the Hudson Valley to say hello to an already Miserable New York City.

Smoke is nothing more and nothing less than incomplete combustion.

3) Dry wood makes things a lot faster.
4) Smaller wood makes things a lot faster.
5) Softer wood also makes things a lot faster, but not necessarily.
6) Warmer wood also makes things faster

[maple flats]

How often do you fuel?
I split mine to wrist size OR smaller, and when I had a half pint I fueled every 6 minutes. As I got a 2x6 or my 3x8 it went to 7 minutes, by the clock. After I added air over fire (AOF) I fueled at 9 minute intervals, still by using a times. For my timer I bought one called "big and loud". The volume was adjustable to 4 different decibel settings, on high I could even hear if I'd gone outside to bring more wood in. https://www.thermoworks.com/extra-big-loud/
I never added more than one armfull at a fueling, likely about 25-30% of what the firebox held, ( a full firebox is about 2/3 to 3/4 full, not 90+%)

[Swingpure]

I found this picture on Smoky Lake Maple to help me visualize the size of wood I need. I have some more splitting to do.

https://share.icloud.com/photos/0a59mPnBoUEcgncCPmxbFcHjg

[Sweet Shady Lane]

Thanks Guys, I will be trying a blower on it this season