Drying Wood Quickly Indoors

[woodgeek]

The bottom line is that if an indoor drying method like this 'works' for you, then you are free to do it. Period.

As a group, we have in the past been unable to agree on an outside seasoning time suggestion, b/c of all the variables of climate, split size etc.
The gen'l guideline 'one year, except dense species which get two' is great (conservative) advice for folks who have the ability to put up a year or two of wood--a
lot of us don't. In reality, with outdoor drying, YMMV. The nature of wood drying has this diminishing returns (decelerating) characteristic, after a fraction
of the time it is most of the way there. So, it is def _possible_ for folks to get a clean/safe burn using wood that has been outside for a good bit less than
a year. To tell folks that it is impossible, or that they shouldn't try stuff and judge for themselves does them a disservice.

Alternatively, the indoor drying process does work (wood in a a dry environment dries, what else would it do?). There have been posters in the past that
have said something akin to 'I bring my just split wood into the house, stack it 5' from the stove, and it is fully seasoned (i.e. it burns great) two days later'.
No one on this thread is suggesting that, in fact it is countering it. In those old threads the methodology was pretty shoddy--folks didn't weigh anything,
own a moisture meter, or have a thermometer on their stove--just said 'yup, goes up really fast after two days in the house, not so much otherwise'.
The service BK is providing is to detail his successful, practical alternative to a year of outside drying. Beyond just telling us 'it works', which we should
believe based on his sage advice over the years, he is providing numerical data that supports his claims (a weight curve), and a timescale--a week or two,
not a day or two.

Whether you decide to try something similar is really up to you once you know the timescale involved. Do you have enough heated, ventilated
space in your house to store 2+ weeks of wood, your wood is reasonably free of bugs/mold to the point you wouldn't lose sleep over visions of beetles
crawling everywhere (thanks pen), and you're already paying an energy/$$ cost to humidify your otherwise too dry house? If the answer is yes, then indoor drying
is an option for you.

It really comes down to volume: for a 24/7 burner, the amounts can be so large, we are talking about a large commitment that eats a lot of indoor space.
If you are burning less than a cord of wood a year, then it is probably not that big a deal.

I also think BK is being conservative--I suggested that a split might be dry through and through after several weeks indoors. Clearly, neither he nor I would
claim that w/o data. But if half of the wood volume is at 15% MC and half is at 25%, it will burn just as well as a uniform 20%MC split. This is the nice thing
about the weight method--it tells you about the average MC, which is the most important thing. Having the outside dryer than the inside helps with take-off,
as BK has demonstrated. This is what has fooled less careful burners into thinking their wood was dry--after one day inside it took off fast (and then died
later). BK is getting enough water mass out that over the whole burn cycle, the splits are functionally equivalent to those dried outside after a reasonably short
(but not conveniently short) length of time.

thanks again BK for the experiment!

 

[gyrfalcon]

Well said, Woodgeek.

I would just add that the other huge factor people seldom want to consider (because it means more work, I guess) in drying time, indoors or out, is the size of the split. When burner after burner confidently and authoritatively announces "Oak takes two or three years to dry"-- yeah, true for really large splits. Split 'em in half and it takes much less time.

 

[Battenkiller]

I had to bring another face cord of birch inside. I'd love to be able to run the entire experiment under the identical starting conditions, but the reality is I have to heat this place with this wood, and it's gotta get dry first. Beside, the extra moisture will do my aching sinuses some good.

The only effect should be a slight rate decrease for a day or two as the wood raises the RH in the room. Should also be about 5º cooler down there for a few days until the wood heats up. I know... more heat loss, but it's happening all at once instead of one load at a time like normal folks experience (and don't even notice). Physics provides no free rides.

Test split is down to 8lbs, 6 1/2 oz. MC is 20.4% wet-basis. It should cross into the promised land of burnability sometime tonight during my sleep. I had to move the stack around to fit in the extra wood and rotate things so I had the wettest wood directly across from the stove for fastest drying. While I was at it, I pulled three different size splits out of the stack, re-split them and took a MC reading with my meter.

Split 1: 3lbs, 14 oz MC outside - 10% MC inside - 24%
Split 2: 5lbs, 4oz. MC outside - 10% MC inside - 24%
Split 3: 9lbs, 7oz. MC outside - 10% MC inside - 25%

How do ya like them apples! I got pics of the splits and the readings if anyone really needs to see them. You can really tell the difference in handling the fresh splits compared to the dry ones. This s*** is heavy when it's wet! The dry stuff hefts like, well... dry wood.

The reason why the splits in the stack are drier is because they have had the fan blowing directly on them the whole time, while the test split is sitting on the scale back in the corner behind the stove. Air circulation speeds up the process considerably.

I intend to run this thing out for the original 21 days planned. That's only good science. But AFAIC, this stuff is dead-ready to burn in anything made.

 

[gyrfalcon]

I had to bring another face cord of birch inside. I'd love to be able to run the entire experiment under the identical starting conditions, but the reality is I have to heat this place with this wood, and it's gotta get dry first. Beside, the extra moisture will do my aching sinuses some good.

The only effect should be a slight rate decrease for a day or two as the wood raises the RH in the room. Should also be about 5º cooler down there for a few days until the wood heats up. I know... more heat loss, but it's happening all at once instead of one load at a time like normal folks experience (and don't even notice). Physics provides no free rides.

Test split is down to 8lbs, 6 1/2 oz. MC is 20.4% wet-basis. It should cross into the promised land of burnability sometime tonight during my sleep. I had to move the stack around to fit in the extra wood and rotate things so I had the wettest wood directly across from the stove for fastest drying. While I was at it, I pulled three different size splits out of the stack, re-split them and took a MC reading with my meter.

Split 1: 3lbs, 14 oz MC outside - 10% MC inside - 24%
Split 2: 5lbs, 4oz. MC outside - 10% MC inside - 24%
Split 3: 9lbs, 7oz. MC outside - 10% MC inside - 25%

How do ya like them apples! I got pics of the splits and the readings if anyone really needs to see them. You can really tell the difference in handling the fresh splits compared to the dry ones. This s*** is heavy when it's wet! The dry stuff hefts like, well... dry wood.

The reason why the splits in the stack are drier is because they have had the fan blowing directly on them the whole time, while the test split is sitting on the scale back in the corner behind the stove. Air circulation speeds up the process considerably.

I intend to run this thing out for the original 21 days planned. That's only good science. But AFAIC, this stuff is dead-ready to burn in anything made.

It is heavy stuff, but of course, so's all high-BTU wood.

Just before whacking myself in the eye with my safety goggles, I almost whacked myself in the face picking up a small split of beech that was a lot lighter than it was when I put it down a few days ago. I've been running my own experiment unintentionally by getting sick for a few days-- not seriously, but enough that I couldn't face dealing with the stove or the wood-- so put on the dollar-bill-burner in the basement and retreated to bed with a hot toddy for a while, leaving about a day's worth of unready, very small splits stacked near the stove to mix in with my dwindling supply of really good rock maple.

With no fan, no stove going, just a baseboard a few feet away and the thermostat set only to 60, these things turned into really nice dry wood in no more than 4 days-- no hissing, no spitting, no drooling foam out the ends, lit up immediately and burned beautifully and thoroughly, practically no coaling at all. My crappy little moisture meter said 13 when I stuck it in, compared to high 20s when I brought it in freshly split. (These things are so small, not worth the effort to split the dry ones again for a fresh reading.)

Yowza! I'm a believer.

 

[RRJ22]

BK
Thanks for the experiment. I have been following it with great interest, mainly because I am way to lazy to take the time to document wood drying! I too have multiple weeks worth of wood in the room with the stove though, because after a minimum of one week inside it burns dramatically better. I had six cords c/s/s by April 15, 2010 of mixed silver maple, cherry, mulberry, and other assorted wood that was stacked outdoors. I upgraded from an old Wonderwood smoke dragon in April to a Summit which took shorter pieces, so I started cutting the wood to size as I brought it up to the roofed woodshed it late Sep. Since I usually try to bring in a few days worth of wood at a time, I noticed that wood stored inside would start getting the drying checks in the fresh cut end in the course of 24-28 hours, which really surprised me because this stuff had been drying outdoors all summer long. My next door neighbor gave me a few armfuls of his wood, which was dry... c/s/s over 5 years ago, and under roof in a super drafty old barn the last several years. His wood burnt hotter and longer than mine, and considering the checking in mine, I assumed mine was wetter than I wanted. I have room in the stove room, (and Pen's bugs aren't a concern) so I brought almost half a cord in and stacked it inside. Observation told me that after one week indoors the checking on the ends had stabilized, and the wood burnt better and the coaling issues almost went away.

My conditions are different than yours, because I also have an OAK. My indoor humidity has hovered around 40 % according to the decorative hygrometer, it feels comfortable and the wife is happy. Hopefully next year I will be able to dry my wood adequately outdoors (it is all cut, and most is already split and stacked) and I won't need to Battenkiln it, but it definitely is making a difference this year. As I already said, your experiment has been fascinating, because you documented with numbers what I was observing.

 

[elmoleaf]

For reference, here's how a kiln dried fire wood operation describes what they need to do to dry wood:
The wood remains in the kilns for 2 days at over 160 degrees; removing over 1000 pounds of water from each cord. This in turn increases the firewood's burning efficiency by nearly l million BTU's per cord over green firewood, and increases the heat value by 25%. The kiln dried firewood is dried to an average of 25% moisture content http://www.coltonenterprises.com/process.htm

 

[SolarAndWood]

http://www.coltonenterprises.com/process.htm

That place is an impressive operation.

 

[Battenkiller]

For reference, here's how a kiln dried fire wood operation describes what they need to do to dry wood:
The wood remains in the kilns for 2 days at over 160 degrees; removing over 1000 pounds of water from each cord. This in turn increases the firewood's burning efficiency by nearly l million BTU's per cord over green firewood, and increases the heat value by 25%. The kiln dried firewood is dried to an average of 25% moisture content http://www.coltonenterprises.com/process.htm

Thank God I can do it at a much slower rate. 160º is mighty toasty. Of course, it sure would eliminate the bug factor.:lol:


Interesting info, and I like the way it is presented. Drives a few important points home:


1. There is a lot of water in a cord of green wood

2. Evaporating all that water doesn't use all that much energy. There's a much bigger difference between red and white oak than 1 million BTU/cord.

3. There are very significant heat losses from other factors besides water evaporation. These would be in the form of lower combustion efficiency and more sensible heat lost up the flue (due to the higher air flows needed). A 25% heating loss comes as no surprise to me.

4. Kiln-dried firewood ain't the same as kiln-dried furniture wood. Note the 25% MC they are selling it at. They don't mention how they are determining the MC, either. If they are doing it by a weight loss estimation and are expressing it as water lost divided by green weight, it is actually at 33% MC dry-basis, which is the way a resistance moisture meter would read.


H-m-mmm..... I wonder how much I can get for the BattenKiln wood? It is now officially below 20% MC wet-basis, 25% dry-basis.

 

[gyrfalcon]

Hmmm. The kiln-dried firewood I've used is done differently, according to the lumber yard's Web site. They say say 180 to 200 for four or five days to get to 15 to 20 percent average MC. (http://www.vermontlumber.com/firewood.php) Perhaps that's because they do bigger pieces (I'm reluctant to call them "splits"), 8 to 10 and sometimes more inches across. Which puzzles me since pretty much the only people who would buy kiln-dried wood in bulk would be people who don't cut their own wood and wouldn't own a splitter to cut them down farther. (And I see to my dismay they've upped their prices by about 40 bucks a cord since I bought from them to get myself out of a jam this winter.)

 

[SolarAndWood]

(http://www.vermontlumber.com/firewood.php) Perhaps that's because they do bigger pieces (I'm reluctant to call them "splits"), 8 to 10 and sometimes more inches across.

What an elegant way to make firewood. BK, have you figured out what the rest of that curve looks like yet? If it takes a week to do what would take a year to do outside, how long does year 2 take?

What do you think about an alcove Battenkiln? Pull the stove out from the wall, put a somewhat low header in a few feet in front of the stove, then circulate the air up around and behind a stack of wood behind the stove. The air then finishes by blowing past the stove on its way to the rest of the house.

 

[Battenkiller]

Hey, Solar... Did you check out the "seasoned" wood Colton is selling? They cut and split about 500 cord in the spring and dump it on the pavement, then they sell it as seasoned in the fall.

Kicks your heapen-hausen's ass! :lol:

I'm calling my buddy up to see when I can check out the firewood kiln-drying operation he oversees. It's nowhere as sophisticated or energy efficient (they use propane-fired heaters and old insulated truck boxes with the same type holding cages), but it should be interesting. I'll go with camera (and moisture meter) in hand and bring back a car full and compare it with the BattenKiln product and give a report.

 

[Battenkiller]

They say say 180 to 200 for four or five days to get to 15 to 20 percent average MC. (http://www.vermontlumber.com/firewood.php) Perhaps that's because they do bigger pieces (I'm reluctant to call them "splits"), 8 to 10 and sometimes more inches across.

Gyrfalcon, you have to remember that they are doing this year round. It's hard to get RH low inside the kiln when you are drawing in air that has more water in it. They need to get the kiln a lot hotter to do that in the summer when there's more water in the air. Temperature does help to increase the diffusion rate inside the wood, but if it ain't evaporating fast enough at the very surface, the wood won't dry fast. Low RH inside the kiln at all times is the main driving force for rapid water removal.

Like I mentioned somewhere above, this works best for me when the weather is at the coldest because that is when there is the least amount of water in the air. I'm not talking RH, I'm talking absolute water content on a grams of water/air volume basis. That's what drives this in the cold weather, and why it won't work well at all in warm weather.

Interesting to see we have yet another professional opinion about the dangers of using wood that is too dry. Maybe it's just a New England phenomenon. %-P

Seasoning and Heat Treatment

Our firewood is kiln-seasoned so that most of the pieces are in the 15 to 20 percent moisture content range, with a general maximum of 25 percent in the bigger pieces. When we dry lumber, we dry it to 6% to 8% moisture content, which is fine for kindling but not for larger pieces of firewood. Trying to burn a number of pieces of firewood at 10% moisture or less can be difficult to control in a wood stove, possibly damaging the stove or your home by causing overheating. The increase in heat value of very dry wood over wood at 20 percent moisture content is small, generally not more than 3 percent, and is outweighed by the potential for overheating.

 

[SolarAndWood]

Kicks your heapen-hausen's ass! :lol:

Ha, producing 1/20th of that last year kicked my ass.

What do you think of the alcove Battenkiln idea? How sensitive do you think the Battenkiln is to temperature?

 

[Battenkiller]

What do you think of the alcove Battenkiln idea? How sensitive do you think the Battenkiln is to temperature?

Sounds like a slow and laborious process to me. You won't get much wood in that space and it will have to be emptied and refilled every 2-3 weeks or so. Knowing how much you feed that King, I don't think you'll come close to meeting your demand. Might want to consider looking for a big-ass pre-EPA radiant heater in the basement. You'll have enough heat down there to drive the process and you'll really be surprised just how much warmer your place will be with heat coming up from underneath as well as from the living space itself.

What seems the best thing is to try to arrange separate drying bins that each hold a one-day supply. Once they all get dry enough to burn, you start burning the wood from one, then refill it the next day and burn the wood in the next compartment. The numbers of compartments = the number of days it takes to bring the wood down to 20%, and you have a perfect rotation with ready wood that is always at the proper MC. I've been thinking of doing this for years now, but every year I start the season without having built it. I'd want mine to be easy to take apart and store since I desperately need the space in the shop. I really welcome the end of the burning season if for no other reason than I get to have my shop back.

For a guy burning less than a cord a month, that means you never have much more than 1/2 cord inside at a time, and the only chance you have of bringing in any unwanted nasty things is in a single day's worth of wood (if you keep your eyes open for them). I never saw anyone here being chastised for bringing in a few days worth of wood, I don't see why what I'm doing is really any different. The only thing I'm doing that hundreds of other burners aren't doing is weighing a piece of wood on a scale every day.

As far as the drying curves, we'll all have to be patient. The data hasn't come in yet, and it's not going as predictably as one might hope for. I'm still losing water from the test split at a fairly rapid rate. Even starting at a RH of 32% several hours after I brought the next load in, the split lost 1/2 ounce in 12 hours. That's the same 1 oz/day rate I've been seeing for a few days now, and I'm not sure what is causing this. That's why it's best to let all the data come in (it's only a bit more than a week away) and then analyze it and begin a discussion about what it all means.

Temperature is critical to this in that you need to artificially drive down the RH in the kiln. A 20º increase in the internal wood temp would speed up the diffusion rate inside the wood very little, but it would make a huge difference to the RH inside the kiln. There is no getting around this. If you can't get the kiln down below 30% RH, drying will proceed too slowly to be useful. Might as well (gasp!) dry it outside.

BTW, I didn't see close to the same spike in RH from the latest wood addition. 32% RH as opposed to the 40% I saw with the first load. And even after the coldest night of the year, there was only a tiny bit of condensation on the single-pane basement windows, and none on the double-glazed ones. Why? Because the wood has been sitting outside drying the whole time. It already had tons of fine end-checking going on when I brought it in, a result of free water moving out of the ends. So much for wood not drying outside in the cold weather.

 

[SolarAndWood]

What seems the best thing is to try to arrange separate drying bins that each hold a one-day supply. Once they all get dry enough to burn, you start burning the wood from one, then refill it the next day and burn the wood in the next compartment. The numbers of compartments = the number of days it takes to bring the wood down to 20%, and you have a perfect rotation with ready wood that is always at the proper MC. I've been thinking of doing this for years now, but every year I start the season without having built it.

That is exactly what I was thinking. The "alcove" would be 15 feet wide with shelving behind the stove. I have some old 20" deep heavy metal warehouse shelving that I have been on the edge of tossing for a while now. Create a trap for the hot air on top of and slightly in front of the stove, put blowers above the stove directing the hot air behind the shelving and back down around through the wood. So, would have something like a cord and a half going all the time. Or 3 if it worked out that I could get away with two rows.

 

[Battenkiller]

The "alcove" would be 15 feet wide with shelving behind the stove. I have some old 20" deep heavy metal warehouse shelving that I have been on the edge of tossing for a while now. Create a trap for the hot air on top of and slightly in front of the stove, put blowers above the stove directing the hot air behind the shelving and back down around through the wood. So, would have something like a cord and a half going all the time. Or 3 if it worked out that I could get away with two rows.

If done correctly, on that scale and in that manner, you have already designed a much better kiln than I have. ;-)

 

[Battenkiller]

Quick update...


Yesterday was the two-week mark. 2/3 of the allotted time for the experiment has passed. Test split is at 23.4% dry-basis, 18.9% wet-basis. Drying has slowed to a crawl - 1/2 to 3/4 oz/day. The split has gone from 10.53 pounds all the way down to 8.25 pounds, and has lost 2.28 pounds of water, which is 0.27 gallons of moisture - over a quart. That's a lot of water in a single split!

I will have to stop measuring the split in ounces lost and use another method. This old produce scale has a scale across the top that gives the amount in dollars and cents as well as in pounds and ounces. By using the $1/lb scale, I can get a good eyeball measurement down to 1/100 of a pound, so I'll stop using the spreadsheet weight formula and just enter the weight directly into the cells in the "Weight" column. Just mentioning it so it won't look suspicious when you look at the data.

You can see by looking at the charts that the RH has been higher for the last several days. That's partly because I brought another face cord of wood in again, but also because it's been warmer outside, and with more actual moisture in the air (snow, sleet, and freezing rain). That may be affecting the drying rate. I'll know better when the RH drops in here again over the next several days. I think it has more to do with the fact that this is, as Woodgeek pointed out, a diminishing-return-for-time-spent proposition. Same thing happens outside, but a lot slower. Once the wood drops the free water, the diffusion-limited water loss rate gets slower and slower with the passage of time. Wood at two years will be only marginally drier than one year old wood.


FWIW there was a huge study about moisture meters that someone linked to in another thread. In reading it, I saw that the method they used to prep the samples (almost 3000 of them!) was to leave them in climate-controlled lab conditions at three different relative humidity levels for at least an entire year. That was after pre-drying at 40ºC until they were close to the target levels. Talk about patience! The idea was to eliminate the moisture gradient inside the samples. In short, it takes a very long time for the wood to get evenly dry all the way from the outside to the very center. And that wasn't for big-ass splits like we love to stoke the stove with. The general rule of thumb in the woodworking trade is to air-dry under cover - stacked and stickered - for at least one year per inch of thickness in order to get the entire board dry through and through. That would be 4-8 years for the size wood I like to burn. Sorry, folks, I just ain't waiting that long.

 

[SolarAndWood]

Wood at two years will be only marginally drier than one year old wood.

In short, it takes a very long time for the wood to get evenly dry all the way from the outside to the very center. And that wasn't for big-ass splits like we love to stoke the stove with. The general rule of thumb in the woodworking trade is to air-dry under cover - stacked and stickered - for at least one year per inch of thickness in order to get the entire board dry through and through. That would be 4-8 years for the size wood I like to burn. Sorry, folks, I just ain't waiting that long.

Did I get the cliff notes right? This is true for 10 lb splits, but how does it scale? I think you and I must like to burn the same thing as my random sample of split this spring ideal splits just ranged from 25 to 35 pounds.

I think my ideal setup may be a mulit-year JagsLeeesque windheapenrowsen with a 2 week stop in the BattenKiln before it hits the stove(s). Then, my current 8 cord under the roof right outside the door solution as a backup for when that doesn't work out quite right. It is a lot less work than I do now and should yield even better results.

 

[Battenkiller]

At 9 PM last night, the BattenKiln wood-drying experiment reached its conclusion. After 21 days, a 10.55 pound split of freshly cut black birch lost a total of 2.52 pounds of water, just sitting in the same place is a very warm and arid environment. It went from an accurately determined moisture content of 57.5% MC (dry-basis) all the way down to 19.9% MC (16.6% MC wet-basis) in a mere three weeks time. Since last night, it has dropped down to 7.98 pounds, and is at 19.1% MC dry-basis, or 16.0% water by weight. It is now exactly at the low end of the EPA range (16-20% water by weight) for water content in the Doug Fir test loads that are used in testing stoves for emissions.

The first photo shows the starting and ending weights. I should have taken the readings directly from the lower scale from the beginning. By looking at the "100" column (see numerals along the bottom), I could have read the weights directly by hundredths of a pound instead of using the spreadsheet formula. In the end, I ended up having to use it because the daily weight loss was less that 1/2 ounce. I adjusted the initial reading that I had entered on the spreadsheet to coincide with was that column read in the starting photo (see lower left ). All direct readings used are highlighted in bright yellow on the spreadsheet. For the remainder of the readings it was close enough to just eyeball the line to the nearest 1/2 ounce and apply the spreadsheet formula.

The column to the far right is the daily ratio of the previous day's weight divided by the current weight. Disregarding the first week's figures, you can see that for most of the last two weeks there was a fairly consistent constant of proportionality of about 0.96, which would indicate that the drying rate might be accurately modeled using an exponential decay function. I'm hoping that the more mathematically astute members who contributed some of the earlier posts might shed a little light on this, since once a constant was established for a given species in a given drying situation, a fairly accurate prediction of when the wood would be finished might be made.

Looking at the data, I'm almost disappointed. I really had no idea that the test split would dip below 20% water by weight at exactly 21 days, but that's the way it played out. Results like that look fudged, but this is not at all the case. Not really a good guess, either, since I originally thought it might get to 25% water by this time if I was lucky. Apparently, black birch is an even faster drying species that I suspected. I will continue to take daily weights of the split until it ceases to dry at the rate of 1 ounce per week. Later in the season I will post the results.


So, guys, look at all the data and give it some thought. Now's the time for discussion if anyone cares to.

 

[gyrfalcon]

[quote author="Battenkiller" date="1295131800"

Gyrfalcon, you have to remember that they are doing this year round. It's hard to get RH low inside the kiln when you are drawing in air that has more water in it. They need to get the kiln a lot hotter to do that in the summer when there's more water in the air.[/quote]

So water in the air is all, which I believe you've been trying to tell us for some time now. I think I finally get it... So that's why it seemed to go faster in these days of well below zero temperatures. Duh.

It's funny how you can observe things but doubt your own observations because you don't know enough to know why it's happening the way it seems to be. That's me and unready firewood drying out within just days next to the stove. I've thought I'd seen this over the last few years, but didn't trust my own sense and figured it must be wishful thinking or some other observer bias.

Since you started posting on your experiment, I've been stacking small splits of my unready wood in open "log cabin" style next to the stove and really paying close attention, and they really are drying out very rapidly, maybe three or four days. That's with no fan. (I've got a good amount of dry rock maple, but it doesn't burn hot enough for these cold mid-winter days, so I need to use as much of the unready beech as possible.)

So profound thanks. Really.

If you're at all, at all inclined to do more experimenting on this, I think it would be particularly fascinating to try it with the same kind of wood-- freshly cut black birch-- but do it without the fan to see just how much of an effect the moving air has on drying rate. And of course, running the experiment with a different species of wood would be awfully interesting, too.

Can't thank you enough for taking the trouble to do this. I do so much prefer facts to guesswork and assumptions.

 

[SolarAndWood]

Can't thank you enough for taking the trouble to do this. I do so much prefer facts to guesswork and assumptions.

+1, thanks for sharing the experiment. The most promising thing I see is that the Daily Ratio has held steady even as the MC has gone down. Makes me think that if you can get to the low 20s MC outside which seems relatively easy, a couple weeks in an appropriately sized Battenkiln for ones heat load will give you a continuous supply of ideal wood without needing 3 years of neat single row stacks outside. For me, I hope it means no stacks at all other than in the kiln.

 

[Battenkiller]

Well, that was a lively little discussion. I expected more naysayers telling me I must have made a mistake because drying wood this fast is just plain impossible.

Six weeks to 20% water content someone claimed? This wood was stove worthy by day 12. How's that crow taste right about now? :-/


Day 26 data and chart below. Test split is at 14.3% water content and still dropping steadily. There is something interesting going on, and I can't for the life of me figure it out. The test split seems to be losing water at a much faster rate than I predicted it would by this time. I expected the shape of the graph to change as the new green wood was brought in, but I didn't expect this later increase in water loss rate.

Unfortunately, I stopped taking the three daily RH readings and averaging them after the three weeks was up. It's a PITA to do, and I actually have a callous on my right pointer finger from holding onto the handle of the sling psychrometer as I spun it for several minutes each day - a meteorological occupational injury. I do have a small chemical indicator that I have learned to rough guess the RH just by sight, and I know that it is very dry down there. At any rate, once this thing stops losing weight for a week, I'm putting it back outside in a dry place to see how much weight it gains by sitting out there in the winter air. That should really spin some heads around. :lol:

Gyrfalcon, I thought I was clear in my explanation. There was no fan on the test split at any time. In fact, it was shielded from the fan by a 6 1/2' tall stack of wood. The fan was on the stack itself, to get it dry for me to burn. I can only say that I think that stuff has even less water left in it than the test split sitting back on the scale all this time. The only air movement the test split received was through natural convection currents... which, I must say, are pretty strong several feet away from a 650º stove.

Solar, I think you have your work cut out for you drying out 30 pounds splits this way. The thickness always works against you, even inside a real lumber kiln. Pre-drying outside will take some of the time off, but just looking at the graphs you can see how much the drying slows down at the tail end of the process. I wouldn't be surprised if it took almost as long to go from 30% to 20% as it would to go from 70% to 30%. I'd do a little improvising right away before you make a major commitment to this and then end up disappointed.



I can't help but notice the attention this thread has gotten so far. 3284 views and 121 replies. Given that, I think a few caveats are in order:



- Unless you thoroughly understand why this is working so well in my case, I'd strongly advise anyone not to attempt this on a large scale. Truth told, when I first started doing this 20 years ago, I didn't understand any of it. I was merely bringing my wood in to make it convenient to load the stove. After a few weeks, I started to notice that it was burning a lot better. After all, green oak don't burn for s***. Getting it to burn at all by using this method was a real epiphany for me, but I didn't fully understand the whole outside RH/inside heat thing for years. A very bright 18 year old apprentice explained it all to me, and it was like a bolt of lightning. Then I fired his ass. Can't have anybody smarter than the boss.

- Different species dry at very different rates. If white oak takes three times as long as cherry to dry outdoors, it will take three times as long to dry indoors. The same chemistry and physics are at play at all times.

- Air movement certainly helps, but the main thing driving this is the lowering of the indoor relative humidity. While increasing the temperature does increase the diffusion rate of water inside the split itself, you aren't really raising it up that much to make that big a difference. The primary thing that getting the air hot does in this improvised kiln is to force the RH indoors to a very low level. In short, if you can't get your storage temps up to at least the mid 80s, this will not work much better than six weeks in the hottest part of the summer. I am always certain that this will occur in my case. Are you certain it will in your situation? If not, try this out in small quantities before you commit to it, or you may be facing a long winter re-splitting your wood to get it to burn well for you.

- As I mentioned above, large splits can take a very long time to dry out. Diffusion rates are inversely proportional to the distance traveled, so they are very rapid for short distances (veneer thicknesses) and tediously long for long distances. Everybody knows this intuitively after a single year of seasoning wood. Split it small if you want it to dry quickly. Which brings me to the final warning...

- You can easily get your wood too dry using this method. Guys... it's a de facto kiln in here. Real kiln-dried wood is not a good thing in almost any stove. Knowing that so many here are of the belief that "the drier the wood, the better it burns" is actually my worst fear here. You're simply not gonna get extra heat out of your stove by getting the wood down to 10% MC... you will get less. You'll either run so hot that you lose tons of heat up the flue, or you'll choke it down and lose lots of wood gases up the flue. Please do not attempt to super-charge your already seasoned wood by doing this or you will be sorry. I'm already at the too dry stage for a lot of this wood. I've been burning off the smaller stuff as fast as I can and saving the huge splits because they dry much slower. You have to really think this through all the time. It's not at all as simple as leaving it out in a covered and breezy location for a couple years. I know some will laugh out loud at this notion, but I am in earnest. This method dries wood fast.. too fast in many cases. Trier beware.

 

[woodgeek]

Much thanks BK for the definitive experiment and nice summary!

 

[Renovation]

Six weeks to 20% water content someone claimed? This wood was stove worthy by day 12. How's that crow taste right about now? :-/

Okay, since you asked for it, one last time.

In one sentence, you demonstrate why thoughtful dissenters--those who could help you clarify your thinking--no longer bother replying to your posts.

Once again you mis-characterize the feedback you've received, blur the distinction between dry and wet basis to your advantage, and insult and condescend to those who took the time to disagree and have a conversation with you.

PM me if you have something friendly or constructive to say. I'll leave the last here word to you, since there's no upside for me in following this thread.

But go ahead, use global warming and safe following distances in your defense, and imply that those who disagree are lazy idiots who are calling you a drug-addled liar. This lazy idiot certainly isn't--I think you're a well meaning, smart guy who lets his emotions get in the way of good science.

As you were.

 

[Battenkiller]

George, I'm really stunned here. I had to go back through this entire thread to see what's got your knickers in a knot...

No offense taken, but I must point out that, by attacking me (for being stoveless) and not my argument, you are making a classic mistake--what I say is true or not simply based on facts and logic, not on how experienced I am, whether I have a stove, or any other personal qualities.

I hope we can all remain civil and friendly, and refrain from personal attacks, for that is what is great about this place, and the standard that I want to maintain.

If I am being rude, inappropriate or wrong, please correct me so that I can learn.

Nothing I said in my last post was directed at anyone in particular, just my way of saying that the predictions of failure were incorrect. I had no idea who said what 3-4 weeks ago. Apparently you were the guy who incorrectly predicted it would take 6 weeks to dry down to 20% MC dry-basis and you assume that I was directing that comment specifically at you? Not true at all.


But then you go on and attack my character with the following?

In one sentence, you demonstrate why thoughtful dissenters—those who could help you clarify your thinking—no longer bother replying to your posts.

Once again you mis-characterize the feedback you’ve received, blur the distinction between dry and wet basis to your advantage, and insult and condescend to those who took the time to disagree and have a conversation with you.

But go ahead, use global warming and safe following distances in your defense, and imply that those who disagree are lazy idiots who are calling you a drug-addled liar. This lazy idiot certainly isn’t—I think you’re a well meaning, smart guy who lets his emotions get in the way of good science.

Just what do you know about my emotional status? I'm a pretty cool-headed guy, but I do have my limits. This is supposed to be fun and educational. Having to deal with multi-pronged attacks against my integrity is not something I care to endure ad nauseum.

To finally answer your question about being rude, inappropriate, or wrong....

In a word, yes, I believe you are.

Now if you have anything useful to add, and if you can handle the heat of my disagreement with your beliefs, feel free to continue to contribute here. I have absolutely no intention of sending you a PM regarding this matter, but if you want to PM me to explain the real cause and nature of this outburst, I will reply in a courteous and thoughtful manner... like I have to dozens of PMs in the past. For the record, I have received my own share of negative comments on the public forums, but never a single negative by PM. Perhaps if folks are so offended by my unintentional insults, they should bring their grievances up in private rather than to try to perform a character assassination in the public view.