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PostPosted: Wed Jul 24, 2019 11:24 am 
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Koa
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So what does it mean when someone says wood is appropriately seasoned for guitar building? Is kiln dried dry enough? I have a moisture metre, if the wood I purchase measures the same as wood I have had in my house (ie. my work bench) for a few years fine to use?

I've seen wood advertised on luthier specific websites as ready to build with. But I'm wondering especially in regards to building solid body electric guitars other than being pre-dimensioned is it any different then buying wood from the local lumber supplier that deals in hardwoods for general woodworking?


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PostPosted: Fri Jul 26, 2019 5:44 am 
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Brazilian Rosewood
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Welcome to the rabbit hole.... It's all marketing spin. KD or kiln dry is the only true specification in the lumber industry, for guitars or otherwise. It's the only thing that can be stamped with the grade by the lumber association. Air dried is a claim and you must trust the source. You will have to ask each source individually what they mean and how they process their stock.

The moisture meter is a good idea but won't tell the complete story as most guitar body woods are 8/4 and your meter will only read maybe 1/2" deep....

From my experiences as a lifelong woodworking pro the best stability is obtained from lumber that was Kiln dried and then left to air season for at least a year preferably 2.

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These users thanked the author B. Howard for the post: Conor_Searl (Fri Jul 26, 2019 11:13 am)
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PostPosted: Fri Jul 26, 2019 11:51 am 
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Koa
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The terms “dried” and “seasoned” are often used synonymously, but this is not really correct. When wood loses moisture from X to Y %, it shrinks — everyone knows that, right? There are published coefficients describing the change in dimension on different axes from green to dry (workable). When wood is then rehydrated back to X%, it swells, but doesn’t NOT return to its original dimension. With each cycle of hydration and dehydration, the changes in dimension become smaller, such that the piece becomes dimensionally more stable. To wood technologists it’s known as hysteresis, to woodworkers it’s known as seasoning.


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These users thanked the author Tim Mullin for the post: Conor_Searl (Fri Jul 26, 2019 12:36 pm)
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PostPosted: Sun Aug 04, 2019 11:54 am 
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Since there is no industry standard. I have found that buying from reputable sources. increases ones chances of being informed correctly. When I buy wood I typically date it, log it into the database and then store it for at least a year. Most of the wood at the lumber store is a different grade of wood, its cut differently such as quarter sawn verses flat sawn. Generally most luthier woods are qtr sawn. Most big box stores are flat sawn and rift sawn. A great book which describes wood in more detail then one could ever want is Understanding Wood.

https://www.amazon.com/Understanding-Wo ... oks&sr=1-3

It's pretty much a necessary read of one is heading down the rabbit hole.

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These users thanked the author dofthesea for the post: Conor_Searl (Sun Aug 04, 2019 4:23 pm)
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PostPosted: Sun Aug 04, 2019 4:23 pm 
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Koa
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Location: Cowichan Valley, BC, Canada
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Country: Canada
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dofthesea wrote:
Since there is no industry standard. I have found that buying from reputable sources. increases ones chances of being informed correctly. When I buy wood I typically date it, log it into the database and then store it for at least a year. Most of the wood at the lumber store is a different grade of wood, its cut differently such as quarter sawn verses flat sawn. Generally most luthier woods are qtr sawn. Most big box stores are flat sawn and rift sawn. A great book which describes wood in more detail then one could ever want is Understanding Wood.

https://www.amazon.com/Understanding-Wo ... oks&sr=1-3

It's pretty much a necessary read of one is heading down the rabbit hole.


Thanks for the suggestion. I added it to the list.


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PostPosted: Thu Aug 08, 2019 7:46 am 
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Brazilian Rosewood
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"Seasoning" is supposed to be more than drying.... It's allowing the internal stresses in the wood to somewhat dissipate and make the wood less apt to shift around. Traditionally - "seasoning" was done in a big covered pile in an area exposed to outdoor weather "seasons"... Cold, hot, wet, dry... After a couple years, the wood finally settles down.


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PostPosted: Tue Oct 08, 2019 11:06 pm 
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Tim Mullin wrote:
The terms “dried” and “seasoned” are often used synonymously, but this is not really correct. When wood loses moisture from X to Y %, it shrinks — everyone knows that, right? There are published coefficients describing the change in dimension on different axes from green to dry (workable). When wood is then rehydrated back to X%, it swells, but doesn’t NOT return to its original dimension. With each cycle of hydration and dehydration, the changes in dimension become smaller, such that the piece becomes dimensionally more stable. To wood technologists it’s known as hysteresis, to woodworkers it’s known as seasoning.

I'm a bit skeptical of seasoning resulting in reduced humidity movement. I've never seen any scientific studies done on it, and especially not with a bunch of pieces from the same batch divided into two groups, one of which is expanded and contracted repeatedly while the other is kept in humidity control. It seems to be more of a "traditional wisdom" thing, which means it may only be the effects of aging... and even that may be a false impression given by weeding out the unstable pieces over time, so what you're left with years later are the ones that were stable to begin with.

The hysteresis effect is definitely real, but it's repeatable. It just means that acclimating from high humidity down to say 50% will have higher moisture content (remain more swollen) than acclimating from low humidity up to 50%. I'm always tormented by luthiers fussing over precise humidity levels but never mentioning that you need to be consistent in your acclimation direction. It makes a 5-10% difference.



These users thanked the author DennisK for the post: Conor_Searl (Wed Oct 09, 2019 11:40 am)
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PostPosted: Wed Oct 09, 2019 9:55 am 
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Cocobolo
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I wouldn't even consider using wood that hadn't aged in my shop for a few years. Except on the rare occasion that I get it from another luthier who I trust like the trade with Clay S. I traded him some 30 year old Coco (I know cause I bought it 30 years ago) for some lovely BRW veneer. I simply wouldn't put my faith in claims from any vendor when it comes to making high dollar instruments.


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PostPosted: Fri Oct 11, 2019 9:05 am 
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Koa
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DennisK wrote:
Tim Mullin wrote:
The terms “dried” and “seasoned” are often used synonymously, but this is not really correct. When wood loses moisture from X to Y %, it shrinks — everyone knows that, right? There are published coefficients describing the change in dimension on different axes from green to dry (workable). When wood is then rehydrated back to X%, it swells, but doesn’t NOT return to its original dimension. With each cycle of hydration and dehydration, the changes in dimension become smaller, such that the piece becomes dimensionally more stable. To wood technologists it’s known as hysteresis, to woodworkers it’s known as seasoning.

I'm a bit skeptical of seasoning resulting in reduced humidity movement. I've never seen any scientific studies done on it, and especially not with a bunch of pieces from the same batch divided into two groups, one of which is expanded and contracted repeatedly while the other is kept in humidity control. It seems to be more of a "traditional wisdom" thing, which means it may only be the effects of aging... and even that may be a false impression given by weeding out the unstable pieces over time, so what you're left with years later are the ones that were stable to begin with.

The hysteresis effect is definitely real, but it's repeatable. It just means that acclimating from high humidity down to say 50% will have higher moisture content (remain more swollen) than acclimating from low humidity up to 50%. I'm always tormented by luthiers fussing over precise humidity levels but never mentioning that you need to be consistent in your acclimation direction. It makes a 5-10% difference.

Now in my 45th year as a forest research scientist, I have a healthy respect for “skepticism”, but before you dismiss my explanation as a “traditional wisdom thing”, you might spend a little more time in the literature on wood physics and water relations.


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These users thanked the author Tim Mullin for the post: Mike_P (Fri Oct 11, 2019 3:59 pm)
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PostPosted: Fri Oct 11, 2019 3:59 pm 
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Koa
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I'm pretty sure that exquisitely flamed red maple stock I've had in my garage for 28 years is well seasoned...being as I'm in Central Texas it's seen some rather wide temperature and humidity variations in that period of time duh


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PostPosted: Sat Oct 12, 2019 8:05 am 
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Koa
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Tim Mullin wrote:
DennisK wrote:
Tim Mullin wrote:
The terms “dried” and “seasoned” are often used synonymously, but this is not really correct. When wood loses moisture from X to Y %, it shrinks — everyone knows that, right? There are published coefficients describing the change in dimension on different axes from green to dry (workable). When wood is then rehydrated back to X%, it swells, but doesn’t NOT return to its original dimension. With each cycle of hydration and dehydration, the changes in dimension become smaller, such that the piece becomes dimensionally more stable. To wood technologists it’s known as hysteresis, to woodworkers it’s known as seasoning.

I'm a bit skeptical of seasoning resulting in reduced humidity movement. I've never seen any scientific studies done on it, and especially not with a bunch of pieces from the same batch divided into two groups, one of which is expanded and contracted repeatedly while the other is kept in humidity control. It seems to be more of a "traditional wisdom" thing, which means it may only be the effects of aging... and even that may be a false impression given by weeding out the unstable pieces over time, so what you're left with years later are the ones that were stable to begin with.

The hysteresis effect is definitely real, but it's repeatable. It just means that acclimating from high humidity down to say 50% will have higher moisture content (remain more swollen) than acclimating from low humidity up to 50%. I'm always tormented by luthiers fussing over precise humidity levels but never mentioning that you need to be consistent in your acclimation direction. It makes a 5-10% difference.

Now in my 45th year as a forest research scientist, I have a healthy respect for “skepticism”, but before you dismiss my explanation as a “traditional wisdom thing”, you might spend a little more time in the literature on wood physics and water relations.

For those skeptical that wood becomes more and more dimensionally stable after repeated cycles of rehydration and drying, I’ve given a link to a recent review paper on standardised lab testing of dimensional stability of wood in service. The phenomenon of stability changing with repeated cycles is discussed quite thoroughly here as it relates to laboratory characterisation of stability in service.:
https://link.springer.com/content/pdf/10.1186%2Fs10086-019-1817-1.pdf
Although wouldn’t call the phenomenon of wood swelling and shrinking less with repeated cycles of hydration and drying “traditional wisdom”, it’s not exactly new. I was first exposed to this in forestry school in the 70s. Being a woodworker even then, it resonated. So, whether you’re building a chair or a guitar, it’s not enough to get the wood down to a certain moisture content; maximum dimensional stability requires repeated cycles of swelling and shrinking.


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PostPosted: Sun Oct 13, 2019 1:22 pm 
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Thanks for the link! Here's another good article from the references: https://www.afs-journal.org/articles/forest/pdf/2005/03/F5031.pdf

So it sounds like after drying from green wood, the first time acclimating up to high humidity and then down to low will make a big difference, and then 2 or 3 more cycles will have diminishing returns, settling into its permanent humidity behavior. But since they were cycling between 90% RH and thoroughly dried with desiccants, it may take more cycles in more mild conditions. And with only one full cycle per year, it really does seem plausible that you could continue seeing benefits for many years.

Thank you Tim! I am no longer skeptical.


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