Need FACTS on wood drying times

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cottonwoodsteve

cottonwoodsteve

Member
Dec 19, 2010
80
Northern California
I would like to know where to get some wood seasoning facts.
All I see and hear is, “age it one year minimum, three years is betterâ€.
This sounds like a bunch of bunk that just gets repeated because nobody has any facts.

My Questions are;
Since most of the moisture comes out of the end grain, how does the length of a split influence the drying time? There is probable a big time difference between a 15 inch long split and a 20 inch long split drying.

What is ratio of moisture leaving end verses sideways? This would also answer does width of split greatly change the time.

How does average ambient humidity affect drying time?

How does temperature of wood affect drying time?

When log moisture is frozen does it stop the process?

My concerns are there is probably a 6 to 1 difference in seasoning times around country.

Lets analyse two scenarios;
#1
Southwest location.
15 inch slong plits
Summer day ambient over 100 F
Low humidity
100% sunshine most days.
Wood stored in direct sunlight. Therefore at 130 F surface temperature.
Longer warmer winter days.
Winter daytime above freezing.

#2
Upper Midwest
20 inch splits
Summer ambient 80 F
High humidity
Frequent clouds and thunderstorms
Wood stored in shed out of sunlight so only at air temp.
Short cold winter days.
Winter daytime below freezing most of the time.

If you look at solar heating or solar panel charts there is about a 4 to 1 difference around the country.
Add to this great humidity differences and shade verses sun.

Bases on all of the above differences, how can we make generic statements of wood aging times?
Can we get some facts on the subject?

I keep my wood, 15 inches long, outside with a clear plastic top cover. It is 100 to 110 for most of the summer. The wood gets up to 130 F in low humidity.
My guess is in 3 summer months the wood will age as much as it would take a year for 20 inch wood, in Minnesota, in a wood shed.
 
cottonwoodsteve said:
All I see and hear is, “age it one year minimum, three years is betterâ€.
This sounds like a bunch of bunk that just gets repeated because nobody has any facts.
I think that these times are good rules of thumb, applicable to most areas of the country. They may be a bit conservative for many areas, but better safe than sorry. Around here, I hear three years mainly in reference to Red Oak, cut fresh, which is the slowest-drying wood AFAIK. Differences can even be very local. If one person lives on top of a hill where there's wind, his wood will dry faster than his neighbor's, a quarter-mile away, who lives in the valley.

My Questions are;
Since most of the moisture comes out of the end grain, how does the length of a split influence the drying time? There is probable a big time difference between a 15 inch long split and a 20 inch long split drying.
That's conventional wisdom here; Shorter splits dry faster. I'm not sure how much faster...

What is ratio of moisture leaving end verses sideways? This would also answer does width of split greatly change the time.
Not sure about the ratio but my wider splits seem like they're not as dry as my 3-4" wide ones. I haven't put the meter on them yet, I'm just going on heft and sound. But that indicate that a lot of drying ends up being through the sides, even if a lot leaves the ends at first...

How does average ambient humidity affect drying time?
I think wet wood will shed moisture fast no matter what the humidity. When the wood gets closer to being dry, the drying rate would slow sooner in a humid environment, I assume.

How does temperature of wood affect drying time?
The higher the temp, the faster drying occurs. Battenkiller (I think) posted a graph that showed drying rates for the various months of the year. Less drying was happening in the coldest months, even though the humidity can be quite low at that time of year.

When log moisture is frozen does it stop the process?
Doesn't stop it (moisture can still sublime) but slows it way down I would think.


Can we get some facts on the subject?
Battenkiller has the facts but has pondered starting a wood consulting business, so we may not be able to get these free facts much longer. :lol:

I keep my wood, 15 inches long, outside with a clear plastic top cover. It is 100 to 110 for most of the summer. The wood gets up to 130 F in low humidity.
My guess is in 3 summer months the wood will age as much as it would take a year for 20 inch wood, in Minnesota, in a wood shed.
I'd think that would be a good guess. And if you're drying Cottonwood, as your username suggests, and the lutefisk-eater is drying Red Oak, there could be a twenty-fold difference. :lol:
Click to expand...
 
Steve,
Since the questions you ask involve core activities of the lumber industry and their profit/production, you might guess that the lumber-drying process gets a lot of study there. You'd be correct.
Some of this info gets published- not hard to find. Some of it, resulting from gummint-sponsored research, is open to the public.
Part of the fun of wood-burning is searching this out, and experimentally confirming or extending it, for your situation.
Not packaged in a silver-bullet that I know of. Enjoy.
 
For starters:
http://en.wikipedia.org/wiki/Wood_drying

Using this as a starting point and the regression coefficients for red oak, I have written a spreadsheet for my oak. I can predict pretty well with controlled conditions. When the wood is outside exposed to the elements, then the accuracy wanes. Too many variables and not enough time or interest in quantifying each variable.

Everybody loves facts, but facts have variables and variables have detractors.
 
Roam around on wood web.com. There is a drying forum and a lot of older articles on wood drying.
 
JimboM said:
For starters:
http://en.wikipedia.org/wiki/Wood_drying

Using this as a starting point and the regression coefficients for red oak, I have written a spreadsheet for my oak. I can predict pretty well with controlled conditions. When the wood is outside exposed to the elements, then the accuracy wanes. Too many variables and not enough time or interest in quantifying each variable.

Everybody loves facts, but facts have variables and variables have detractors.
Click to expand...

Jim, would love to see that spreadsheet!
 
I find the facts interesting but am much more interested in confidence intervals. I know that 18" good sized splits in an uncovered pile in my location will be dry in 3 years. Before I was three plus years ahead, I split smaller and stacked in single rows so that I knew I would have enough dry wood to make it through the winter. The further I get ahead, the bigger I split.
 
Keep in mind that whatever facts you come across are likely to vary for your situation depending on any number of variables (temp, wind patterns, type of wood, size of splits, etc) so take any facts you come across with a grain of salt. If you really want facts for your situation I would recommend getting a moisture meter and keeping some data of your own. That way you can be certain that the info is right for you and not someone in a much cooler or wetter climate.
 
muncybob said:
JimboM said:
For starters:
http://en.wikipedia.org/wiki/Wood_drying

Using this as a starting point and the regression coefficients for red oak, I have written a spreadsheet for my oak. I can predict pretty well with controlled conditions. When the wood is outside exposed to the elements, then the accuracy wanes. Too many variables and not enough time or interest in quantifying each variable.

Everybody loves facts, but facts have variables and variables have detractors.
Click to expand...

Jim, would love to see that spreadsheet!
Click to expand...

I PMd you.
 
cottonwoodsteve said:
I would like to know where to get some wood seasoning facts.
All I see and hear is, “age it one year minimum, three years is betterâ€.
This sounds like a bunch of bunk that just gets repeated because nobody has any facts.
Click to expand...

I don't know, Steve, but this came across as pretty demanding. For the vast majority of us, rules of thumb are good enough.
There are too many variables with hundreds of species of trees, climates and weather, even elevation, to come up with a bible for drying times. To declare years of experience mere "bunk" and say that "nobody has any facts" is rather insulting. If 'nobody has any facts' why are you insisting that the members of this forum give you the facts and/or do your research for you. What are you looking for? A spread sheet that gives you the exact time in days and hours to dry a specific species of tree? Let us know how that works out for you. Feel free to share your data when you complete your dissertation. There are probably folks here who DO have all the answers, but the answers only apply to their location and the type of wood they burn. It will have no bearing on your own situation.

I'm thinking most of us are not nearly so retentive, anal or otherwise, in our wood handling, drying and burning techniques.

The members here go out of their way to help, offer advice and critique, and to share our good fortunes or give a pat on the back when appropriate. Lighten up a little, relax, do some reading, and enjoy the experience. We don't give college credit for the learning experiences gained here.

Cheers!

Kenster
 
Kenster said:
We don't give college credit for the learning experiences gained here.
Click to expand...

No, but I would have appreciated a GED after my first season without a sizzler :lol:
 
I don't think you will get hard facts unless you consult lab results. Battenkiller is leading the charge with this kind of information, but they are "lab" results nonetheless and may have little to do with your particular situation. Basic premises found here are VERY sound though. You could do worse than to just adjust the conventional wisdom found here to your in situ conditions.

I have had wonderful results following the basic guidelines found here, both in a reduction in the amount of wood burned and the status of my chimney liner. And yes, I just covered my wood in the last few weeks :)
 
Kenster said:
cottonwoodsteve said:
I would like to know where to get some wood seasoning facts.
All I see and hear is, “age it one year minimum, three years is betterâ€.
This sounds like a bunch of bunk that just gets repeated because nobody has any facts.
Click to expand...

I don't know, Steve, but this came across as pretty demanding. For the vast majority of us, rules of thumb are good enough.
There are too many variables with hundreds of species of trees, climates and weather, even elevation, to come up with a bible for drying times. To declare years of experience mere "bunk" and say that "nobody has any facts" is rather insulting. If 'nobody has any facts' why are you insisting that the members of this forum give you the facts and/or do your research for you. What are you looking for? A spread sheet that gives you the exact time in days and hours to dry a specific species of tree? Let us know how that works out for you. Feel free to share your data when you complete your dissertation. There are probably folks here who DO have all the answers, but the answers only apply to their location and the type of wood they burn. It will have no bearing on your own situation.

I'm thinking most of us are not nearly so retentive, anal or otherwise, in our wood handling, drying and burning techniques.

The members here go out of their way to help, offer advice and critique, and to share our good fortunes or give a pat on the back when appropriate. Lighten up a little, relax, do some reading, and enjoy the experience. We don't give college credit for the learning experiences gained here.

Cheers!

Kenster
Click to expand...

Ditto Kenster!!!
 
well, if you want to get down to the scientific nitty gritty of drying times, there are going to be WAY too many variables to control. This year, for instance, being a very wet year and all the talk of a muted fall given higher moisture content in leaves/trees would probably mean a fresh cut tree would likely need more drying time than a tree freshly cut in a drier year. How much? who knows... I think the 1-2 year drying time for most woods is a good guideline to prevent problems. Oak, probably tack a year on to those numbers.
There's probably a LOT of info out there on wood drying but keep in mind that everybody's starting point is different... an oak in the NW isn't the same as an oak in the SE.

Good luck!
 
Kenster said:
If 'nobody has any facts' why are you insisting that the members of this forum give you the facts and/or do your research for you.

There are probably folks here who DO have all the answers, but the answers only apply to their location and the type of wood they burn. It will have no bearing on your own situation.
Click to expand...

Bravo

Yeah, like none of us know anything. Bottom line is I can give you all the scientific studies and drying theory you can wrap your mind around, but if you want specifics you are going to have to figure those out on your own.

FWIW the above Wiki link to "Wood Drying" is a nice, concise, and scientific treatment to the theories behind it all, but it won't help you any more than simply knowing the EMC in your area. Since drying rates are in a linear relationship to RH, and EMC is directly related to average RH in your area, just do the math. If you don't know how, just ask that question and I or several others here can help you figure it out, but don't go discounting time-honored rules-of-thumb as bunk. They work as well as anything else in the real world, the rest is just for inquiring minds that want to know why they work. Experience definitely counts.

Even in a lab setting, you need a lot of experience just to tell if what you are observing is a real effect or merely artifact. You also need tons of real-life experience to develop effective experimental designs, calibrate machinery, optimize the methodology, interpret the statistics correctly, and present them in a cohesive manner.


That said, here's another very informative contribution recently posted by another member. It's from those good old boys at the Forestry Service, and it contains 144 pages of goodies (facts, tables, charts, theory, advice, etc). If you get lost, come back with specific questions and we will try to address them as best as we morons are able to. ;-P


http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr118.pdf
 
The last post by Inferno had a good link.
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr118.pdf
Lots of detailed info that I don't have time to digest right now but one thing stood out.
There is a map of the east US area with drying times. I assume this takes into account average temperature, humidity, and other details. This is the type of info that is very important but nobody seems to care about.
The map shows some places you can dry wood in 4 months that would take 12 months in other places.
I assume if I could find a map like that for the dryer western US it would be even more extreme compared to the east US.
So this confirms my concerns. There is a 3 to 1 difference in the cooler more humid parts of the US. Imagine what it would be if it included the dryer west parts. Maybe easily a 6 to 1 difference, 8 to 1 difference?

Lets take even the conservative 3 to 1 difference. If I cut some Oak or Eucalyptus in the spring, leave it outside in an exposed area with some wind, at 100 to 110 F, it will probably be ready to burn by November. If I had money I would cut a controlled block, and get a moisture meter. Then send half of the controlled block to the long drying time area and have someone there age it and test it. They we could graph the moisture comparison.

It is easy to find charts for gardening and solar energy. Gardening is broken down into zones 1 thru 9. What we need is a simular wood burners map with wood aging time zones 1 thru 9, plus a multiplier for stored inside or outside direct exposure.

This is the whole point I was getting at. There is probable easily a 6 to 1 difference in drying times across the US. That's why I got tired of always hearing one size fits all statements.

I live in the upper central valley of California. It gets about 40 inches of rain a year mostly in winter. For 3 months in the summer it is hot and dry. Always over 100 F, lots of 105 F, some 110 F and one or two peaks of 112 to 115 F. Very low humidity. It probably drys wood pretty darn fast.
 
cottonwoodsteve said:
The last post by Inferno had a good link.
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr118.pdf
Lots of detailed info that I don't have time to digest right now but one thing stood out.
There is a map of the east US area with drying times. I assume this takes into account average temperature, humidity, and other details. This is the type of info that is very important but nobody seems to care about.
The map shows some places you can dry wood in 4 months that would take 12 months in other places.
I assume if I could find a map like that for the dryer western US it would be even more extreme compared to the east US.
So this confirms my concerns. There is a 3 to 1 difference in the cooler more humid parts of the US. Imagine what it would be if it included the dryer west parts. Maybe easily a 6 to 1 difference, 8 to 1 difference?

Lets take even the conservative 3 to 1 difference. If I cut some Oak or Eucalyptus in the spring, leave it outside in an exposed area with some wind, at 100 to 110 F, it will probably be ready to burn by November. If I had money I would cut a controlled block, and get a moisture meter. Then send half of the controlled block to the long drying time area and have someone there age it and test it. They we could graph the moisture comparison.

It is easy to find charts for gardening and solar energy. Gardening is broken down into zones 1 thru 9. What we need is a simular wood burners map with wood aging time zones 1 thru 9, plus a multiplier for stored inside or outside direct exposure.

This is the whole point I was getting at. There is probable easily a 6 to 1 difference in drying times across the US. That's why I got tired of always hearing one size fits all statements.

I live in the upper central valley of California. It gets about 40 inches of rain a year mostly in winter. For 3 months in the summer it is hot and dry. Always over 100 F, lots of 105 F, some 110 F and one or two peaks of 112 to 115 F. Very low humidity. It probably drys wood pretty darn fast.
Click to expand...


Bunk!
 
cottonwoodsteve said:
This is the whole point I was getting at. There is probable easily a 6 to 1 difference in drying times across the US. That's why I got tired of always hearing one size fits all statements.
Click to expand...

I never take that away from most seasoning conversations. Most of us say there are a lot of variables and once you have a season or two under your belt you'll know how long it takes for YOU to season your wood. One season of higher than normal RH, colder temps, warmer temps can change everything.

Starting out the "get a couple years ahead" is a sound advice imo. This is wood seasoning this isn't brain surgery, give it two-three years and not matter what it'll probably be good to go.
 
cottonwoodsteve said:
I live in the upper central valley of California. It gets about 40 inches of rain a year mostly in winter. For 3 months in the summer it is hot and dry. Always over 100 F, lots of 105 F, some 110 F and one or two peaks of 112 to 115 F. Very low humidity. It probably drys wood pretty darn fast.
Click to expand...

I believe it.

Average RH in my area is close to 80% year round. In your area it is about 20% RH for most of the year. Lucky you. Wood will thoretically dry four times as fast as it will here just because of the difference in RH alone. Your climate in the summer is just about like my basement in the middle of the winter, only hotter.

Dense wood like oak, hickory, and hard maple will dry down to 20% MC in three weeks in my basement when cut 18" and split 4-6". Yours should dry even faster.

As for split length, wood dries 10 to 15 times as fast from the ends as it does from the sides, depending on species. Cutting wood shorter also reduces the amount of case hardening that will trap moisture in the wood for a longer time.

Is this helpful?
 
Battenkiller said:
As for split length, wood dries 10 to 15 times as fast from the ends as it does from the sides, depending on species. Cutting wood shorter also reduces the amount of case hardening that will trap moisture in the wood for a longer time.
Click to expand...

Okay, then. I'm confused. I always thought it would dry much faster, or more efficiently, from the sides. If this is not the case, why do we split?
 
Why do we split if it doesn't affect drying time?
To make it easier to carry, to make it fit through the stove door. and it lights off quicker.
The image below shows that even if I cut it into 15 inch length I could not lift it and it wouldn't fit into the house door much less the wood stove door.
 

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That goes against every thing I've ever read and experienced. Virtually every post about drying wood says that the wood does not start drying out until it is split. That rounds can be stacked for years but will lose very little moisture until they are split.

Just to clarify, you're saying that a 12 inch round, for example, will dry out quicker if left in the round than it will if it is split into halves or quarters? That just makes no sense to me. It's as if I've just been told that the world is flat after all.
 
Kenster said:
Just to clarify, you're saying that a 12 inch round, for example, will dry out quicker if left in the round than it will if it is split into halves or quarters? That just makes no sense to me.
Click to expand...

Not what I said at all. Wood dries from all exposed surfaces. Fastest from the ends, slowest through the bark. Splitting exposes the inner wood and also dramatically increases the surface area exposed to drying forces. It also decreases the sectional thickness. This reduces the distance that water within the split has to diffuse to reach the air touching the wood surface.

It makes perfect sense to split wood to decrease the drying time. However, it is a fallacy that bucked rounds won't dry unless split. They will, but since they are only drying from the ends the drying will proceed measurably slower than if it is split.
 
Lord, I thought the world as I knew it was coming to an end. Thanks for clarifying BK. When you said that wood dries faster through the ends than through the "sides" I thought you meant the inside split sides, rather than the bark.

I can sleep soundly tonight knowing that all is right with the world (except the part where Cottonwood Steve says the only reason we need to split wood is to make it more portable.)
 
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