I had a cord of freshly cut and split black birch delivered here last week. I stacked up half of it outside and the other half inside (Sunday afternoon, January 2). Monday night I went out and grabbed a fairly dense and sopping wet medium-size piece and brought it in and took a small slice off the end to get rid of any wood that may have dried while it was outside the last couple days. Then I took a 2-3" slice off the end and weighed it on the old hippie herbal remedy weigh station (triple beam scale). Came out to just a hair under a pound - 445.4 grams.
I placed the remainder of the split on my old produce scale, and it weighed 10 pounds, 8 1/2 ounces (10.53 pounds). I will leave it right there and weigh it each day and record the weight to get a drying curve established. I will also take the relative humidity (RH) every day at the same time that I weigh it and record the result. I have a large commercial floor fan blowing on the stack 24/7 to keep air moving through it. It seems to be doing a very good job of moving air through the spaces between the splits so they can dry faster, just like being outside in a constant breeze.
I used the smaller sample to determine the moisture content of the sample split to get a baseline. This stuff is way too wet to even think of using a resistance-type moisture meter on it. I used the much more accurate oven-dry method to get the MC within a couple tenths of a percent. I will use that info to evaluate the moisture content of the larger split as it dries out over the next few weeks.
I thought this was an exceptionally dense piece of wood. I took it into the kitchen, filled the sink and dropped it in. Sank like a rock.
I then took it out of the water and went downstairs to chop it into little pieces with my trusty kindlin' meat cleaver (had to make sure I saved every little piece). That would allow it to dry much quicker. I wanted to make sure I went slow with this one since the last time I did this I just wanted to demonstrate the method to the membership here. This one's for the books. Any unwanted charring of the wood will cause the sample to lose some volatile substances, skewing the result to show a higher initial MC than it really had.
I started out using my kitchen microwave to dry it, but that was taking forever and it was getting late, so I did it old school - overnight in an oven set at 215ºF. Woke up and weighed the pieces on my triple beam - 282.9 grams. There was no evidence of charring anywhere, so I think the stuff is a good.
445.4 - 282.9 = 162.5 grams water lost = 36.5% water by weight (wet-basis), or 57.4% MC (dry-basis). Not as wet as it looked, but certainly twice as high as any moisture meter will allow accurate measurement.
So, the 10.53 pound split sitting on the scale in the basement at 36.5% water contained 3.84 pounds of water when I placed it there and 6.69 pounds of wood fiber. This is the figure that is needed to compute all further moisture loss using the changing weight alone to make the calculations. The ramifications of this are that anyone can accurately determine the MC of there firewood at any time if they take a few representative samples during the season, weight them, determine the MC at that point, compute the dry fiber content, and use this at any point in the future to calculate the MC of their wood merely by weighing it. No meter needed, no re-splitting, no sorting through piles looking for suitable splits. And you don't need to be artificiality drying your wood indoors to take advantage of this technique.
The RH in the shop was determined using a Taylor sling psychrometer. On day one, dry-bulb temp was 83º, wet-bulb temp was 66º. 17º wet-bulb depression at that temp = 40% RH. Not as low as it will get when all the wood starts drying out. The day before I started this I took in 1/2 cord from the same soaking wet load of black birch and stacked it 5' high, 42" in front of the stove (even with soaking wet wood I adhere religiously to clearances) with a large fan blowing against the back of it. On day one it was acting as an gigantic organic humidifier with the wonderful scent of wintergreen emanating from it.
Results so far after four days of drying:
Day # Weight (lbs) Water Wt (lbs) Fiber Wt (lbs) Rel. Humidity MC (dry-basis) MC (wet-basis)
One: 10.53 3.84 6.69 40% 57.4% 36.5%
Two: 10.03 3.34 6.69 35% 49.9% 33.3%
Three: 9.56 2.87 6.69 34% 42.9% 30.0%
Four: 9.38 2.69 6.69 30% 40.2% 28.7%
Five: 9.13 2.44 6.69 28% 36.5% 26.7%
As you can see, the 10 1/2 pound split lost a full 1/2 pound of water in one 24 hour period, 6 ounces the next day, 4 ounces the day after that and 3 1/2 ounces since last night. MC at present is 36.5% (dry-basis), or 26.7% (wet-basis). Just to compare methods, I grabbed a similar size split from the inside stack (it had been inside one extra day), split is and measured the MC. It measured at 34% MC on the meter, which is a dry-basis measurement. Pretty durn close, eh?
As my indoor stockpile of wood dries more and colder weather hits, RH down there should drop to about 20%, at which point all of the wood will be fairly well dried out and ready to burn (25% dry-basis, 20% wet-basis).
I placed the remainder of the split on my old produce scale, and it weighed 10 pounds, 8 1/2 ounces (10.53 pounds). I will leave it right there and weigh it each day and record the weight to get a drying curve established. I will also take the relative humidity (RH) every day at the same time that I weigh it and record the result. I have a large commercial floor fan blowing on the stack 24/7 to keep air moving through it. It seems to be doing a very good job of moving air through the spaces between the splits so they can dry faster, just like being outside in a constant breeze.
I used the smaller sample to determine the moisture content of the sample split to get a baseline. This stuff is way too wet to even think of using a resistance-type moisture meter on it. I used the much more accurate oven-dry method to get the MC within a couple tenths of a percent. I will use that info to evaluate the moisture content of the larger split as it dries out over the next few weeks.
I thought this was an exceptionally dense piece of wood. I took it into the kitchen, filled the sink and dropped it in. Sank like a rock.
I then took it out of the water and went downstairs to chop it into little pieces with my trusty kindlin' meat cleaver (had to make sure I saved every little piece). That would allow it to dry much quicker. I wanted to make sure I went slow with this one since the last time I did this I just wanted to demonstrate the method to the membership here. This one's for the books. Any unwanted charring of the wood will cause the sample to lose some volatile substances, skewing the result to show a higher initial MC than it really had.
I started out using my kitchen microwave to dry it, but that was taking forever and it was getting late, so I did it old school - overnight in an oven set at 215ºF. Woke up and weighed the pieces on my triple beam - 282.9 grams. There was no evidence of charring anywhere, so I think the stuff is a good.
445.4 - 282.9 = 162.5 grams water lost = 36.5% water by weight (wet-basis), or 57.4% MC (dry-basis). Not as wet as it looked, but certainly twice as high as any moisture meter will allow accurate measurement.
So, the 10.53 pound split sitting on the scale in the basement at 36.5% water contained 3.84 pounds of water when I placed it there and 6.69 pounds of wood fiber. This is the figure that is needed to compute all further moisture loss using the changing weight alone to make the calculations. The ramifications of this are that anyone can accurately determine the MC of there firewood at any time if they take a few representative samples during the season, weight them, determine the MC at that point, compute the dry fiber content, and use this at any point in the future to calculate the MC of their wood merely by weighing it. No meter needed, no re-splitting, no sorting through piles looking for suitable splits. And you don't need to be artificiality drying your wood indoors to take advantage of this technique.
The RH in the shop was determined using a Taylor sling psychrometer. On day one, dry-bulb temp was 83º, wet-bulb temp was 66º. 17º wet-bulb depression at that temp = 40% RH. Not as low as it will get when all the wood starts drying out. The day before I started this I took in 1/2 cord from the same soaking wet load of black birch and stacked it 5' high, 42" in front of the stove (even with soaking wet wood I adhere religiously to clearances) with a large fan blowing against the back of it. On day one it was acting as an gigantic organic humidifier with the wonderful scent of wintergreen emanating from it.
Results so far after four days of drying:
Day # Weight (lbs) Water Wt (lbs) Fiber Wt (lbs) Rel. Humidity MC (dry-basis) MC (wet-basis)
One: 10.53 3.84 6.69 40% 57.4% 36.5%
Two: 10.03 3.34 6.69 35% 49.9% 33.3%
Three: 9.56 2.87 6.69 34% 42.9% 30.0%
Four: 9.38 2.69 6.69 30% 40.2% 28.7%
Five: 9.13 2.44 6.69 28% 36.5% 26.7%
As you can see, the 10 1/2 pound split lost a full 1/2 pound of water in one 24 hour period, 6 ounces the next day, 4 ounces the day after that and 3 1/2 ounces since last night. MC at present is 36.5% (dry-basis), or 26.7% (wet-basis). Just to compare methods, I grabbed a similar size split from the inside stack (it had been inside one extra day), split is and measured the MC. It measured at 34% MC on the meter, which is a dry-basis measurement. Pretty durn close, eh?
As my indoor stockpile of wood dries more and colder weather hits, RH down there should drop to about 20%, at which point all of the wood will be fairly well dried out and ready to burn (25% dry-basis, 20% wet-basis).
