Wood seasoning

[seangil]

am looking for advice on how to best store tonewoods for tops, backs, and sides. I have been keeping my wood on a shelf indoors stacked (on sticks) in an area where I mostly keep the humidity under control. I have three different hygrometers, which all give me different numbers, but I think that I mostly manage to stay in the 45% - 55% range with occasionally going down to a little below 40% during the winter. My wood is all purchased already milled from places like LMI and Hibdon. Temperature probably ranges from high 50s F - low 80s F over the year.

I was reading about seasoning, however, and came across some threads - including from a very well-respected luthier - talking about seasoning and recommending that wood actually needs to be exposed to wide fluctuations in temperature and humidity to be seasoned. Their ideal storage would actually be a sheltered location outside. I am now uncertain about what I should do with my wood. Any advice?

My options are:

- Keep in its current location;
- Place in my attic which probably goes 10 degrees higher / lower in temperatures and humidity trends to match outside (although it will get quite high during the summers);
- Buy one of those inexpensive DIY sheds from places like Home Depot that are normally for garden tools to build in my backyard.

How would you rank these options and how much difference would they make?

Thanks

Sean

[redir]

I keep boards and billets out in my outdoor workshop stacked and stickered to season through cold winters and hot summers but once they are resawn to guitar sized timbers they go into the humidity controlled shop for years before they are used.

So I would not store your already cut wood anywhere else then what you are currently doing.

I don't sticker them once they are seasoned and resawn either, just stack. Don't store them near a window either especially stickered because you will get different coloration.

You should also calibrate your hygrometers. There are many ways to do it. Just look up "wet bulb calibration" and find ideas for that. I have a good one and a few cheap ones and also a device for calibrating them which I do once a year. On the cheap one I simply take a Sharpie and mark on it where 45%RH is. It was off by about 10% so it's significant.

[charles Tauber]

I think it depends partly on how much wood you have to store and for how long you expect to store it. If you only have a few backs, sides and tops that you plan to use in a year or two, I'd keep it where it will be used to build. If you have a lot more than that and expect to season it for a decade or two, outside storage might be fine, properly stickered and weighted to stay flat.

Keep in mind that drying and seasoning are two different things. The humidity range that you state is too large a variation to build in. Braced tops that are convex one day can be concave the next. One can't do close fitting work with materials that are constantly changing size and shape.

Regardless of how seasoned your wood is, it will need to be acclimatized to the humidity level at which you will do the guitar building. You need to be able to have reasonably accurate control of that environment. That starts with reasonably accurate humidity measurements.

Neither the humidity control nor the humidity measurement need to be especially elaborate or extensive. The humidity control can be as simple as a large box with light bulbs, in which you keep the materials when not actively working on them, or a closet with a room dehumidifier, for storage when not actively working on parts. The best solution will depend on your climate.

[seangil]

Thanks for the advice. For any given period, I can usually keep the humidity in about a 5% range. My gaps usually come when the de-humidifier gets full or during winter when it dries out more and I don't yet have a good solution for adding humidity to my workspace.

Can I ask what you mean about seasoning vs. drying? I understand the conceptual difference, but not quite sure how to apply it. Should I consider wood that I purchase from suppliers like LMI and Alaska Tonewoods and Hidbon to be seasoned? Do I need to worry about exposing it to extremes to get dimensionally stable?

At the moment, my wood supply will last me some years, but probably not as much as a decade. I am tempted by the idea of buying some extra tops and such with the idea of letting them season for a decade since I recently acquired some wood that is 20 years old and it is REALLY different from stuff that I bought last month. However, it's only worth thinking about storing for a decade or more if I have the right equipment/set up such that it would age properly. Hence my question.

On the calibration, I am really confused. I have done tests to calibrate two electronic hygrometers. They both pass the test as being calibrated and then differ on their readings of the same place by 5%. Put them in a bag to test and they agree. Put them on a table in an open room and they disagree. I have no idea which one is accurate and don't want to keep buying hygrometers until I find three that agree!

[charles Tauber]

Originally Posted by seangil

I don't yet have a good solution for adding humidity to my workspace.

Evaporative humidifiers, usually. Depending on your circumstances, letting the room be a little cooler can increase the relative humidity.

Can I ask what you mean about seasoning vs. drying? I understand the conceptual difference, but not quite sure how to apply it. Should I consider wood that I purchase from suppliers like LMI and Alaska Tonewoods and Hidbon to be seasoned? Do I need to worry about exposing it to extremes to get dimensionally stable?

In simple terms, drying is eliminating excess moisture from wood. Wood absorbs and desorbs moisture in response to the humidity level of its environment. When wood is cut, it has much more moisture in it than its surrounding air, hence it loses moisture. It will continue to do so until it reaches an equilibrium of its moisture content and that of the surrounding air. When that equilibrium has been reached, the wood is "dry". If you change the humidity of the surrounding air, the wood will change moisture content to achieve equilibrium. So, wood that is outdoors in a higher ambient humidity, when brought indoors to a lower ambient humidity, the wood will "dry", losing moisture.

Seasoning is permanent change to the composition and properties of wood. It happens gradually, naturally over time. It has generally been accepted that using older wood - wood that has seasoned - produces better sounding instruments. It isn't clear that there is scientific evidence to support that belief, but it is a widely held belief. There is no specific time period that is accepted as to when wood has been "aged" or seasoned: "older is better" is the usual adage.

In recent years, some have tried to artificially achieve similar changes to the wood by thermally treating the wood, a process called torrefaction. The jury is, perhaps, still out on the long-term advantages or disadvantages of doing so. Some believe that one gets the sound of an aged guitar on a new guitar built using wood that has be subject to torrefaction.

it's only worth thinking about storing for a decade or more if I have the right equipment/set up such that it would age properly. Hence my question.

The wood will age regardless of what you do. Some, as you know, argue that it ages faster if subject to environmental fluctuations. I'm not aware of hard science that supports or refutes that.

On the calibration, I am really confused. I have done tests to calibrate two electronic hygrometers. They both pass the test as being calibrated and then differ on their readings of the same place by 5%. Put them in a bag to test and they agree. Put them on a table in an open room and they disagree. I have no idea which one is accurate and don't want to keep buying hygrometers until I find three that agree!

First, what test did you do? A common test is to use a specific salt solution that produces a known relative humidity in a closed environment. If you performed the test using a salt that provides a standard at 75% relative humidity (RH), that doesn't tell you much about how accurately the instrument will read at 40 % RH - 40% isn't at or near the value that you tested. For more accurate results, ensure you use a salt that will provide a value nearer the range you intend for the hygrometer to measure, or use a different testing method, such as a sling hygrometer.

Luthier Simon Fay put together a very good pictorial instruction on how to perform a salt test: https://www.acousticguitarforum.com/...d.php?t=575903

Regardless, if they both read the same within 5%, that is probably close enough.

[JonWint]

Martin stored wood in the attic when the North Street factory was being used for manufacturing. Several years’ worth of wood was there enduring an annual temperature range from -10 degrees F to 120+ degrees F. Daily fluctuations could be 50 degrees. Humidity control: what’s that?

It’s been said that some good sounding guitars were built during that period.

[Howard Klepper]

Originally Posted by seangil

am looking for advice on how to best store tonewoods for tops, backs, and sides. I have been keeping my wood on a shelf indoors stacked (on sticks) in an area where I mostly keep the humidity under control. I have three different hygrometers, which all give me different numbers, but I think that I mostly manage to stay in the 45% - 55% range with occasionally going down to a little below 40% during the winter. My wood is all purchased already milled from places like LMI and Hibdon. Temperature probably ranges from high 50s F - low 80s F over the year.

I was reading about seasoning, however, and came across some threads - including from a very well-respected luthier - talking about seasoning and recommending that wood actually needs to be exposed to wide fluctuations in temperature and humidity to be seasoned. Their ideal storage would actually be a sheltered location outside. I am now uncertain about what I should do with my wood. Any advice?

My options are:

- Keep in its current location;
- Place in my attic which probably goes 10 degrees higher / lower in temperatures and humidity trends to match outside (although it will get quite high during the summers);
- Buy one of those inexpensive DIY sheds from places like Home Depot that are normally for garden tools to build in my backyard.

How would you rank these options and how much difference would they make?

Thanks

Sean

That luthier had it right. Bring the sets into your controlled shop environment a couple of months before you build with them. You aren't hurting the woods now, but you are preventing them from getting the full benefit of seasoning.

[charles Tauber]

Originally Posted by JonWint

It’s been said that some good sounding guitars were built during that period.

Since no harm comes to the wood by doing so, and there is no cost to do so, other than just storage space, sure, why not do it.

However, that isn't "proof" that one gets a better sound by letting wood seasonally cycle. One can make fine instruments if one does and if one doesn't.

[Howard Klepper]

Originally Posted by charles Tauber

Since no harm comes to the wood by doing so, and there is no cost to do so, other than just storage space, sure, why not do it.

However, that isn't "proof" that one gets a better sound by letting wood seasonally cycle. One can make fine instruments if one does and if one doesn't.

The issue is not sound, Charles. It's stability, and there is plenty of evidence (it's always hard to know what someone is willing to count as "proof" outside of a formal system) that wood which has been through more seasonal cycles is more stable.

[Alan Carruth]

Charles Tauber wrote:
"Seasoning is permanent change to the composition and properties of wood. It happens gradually, naturally over time. It has generally been accepted that using older wood - wood that has seasoned - produces better sounding instruments. It isn't clear that there is scientific evidence to support that belief, but it is a widely held belief. There is no specific time period that is accepted as to when wood has been "aged" or seasoned: "older is better" is the usual adage."

Actually, there is good science on this going back to the 1950s, it just took a long time to filter up to us from the museum curators. There is a summary of it in the Catgut Acoustical Society 'Journal', Vol.4, #3, (Series II), May 2001, 'Some Aspects of Wood Structure and Function' by Ephraim Segerman, pp.5-9.

One of the things that changes with seasoning is that the hemicellulose 'filler' in the lignin 'glue' that holds things together breaks down slowly over time. The process seems to speed up with higher moisture levels and temperatures. Since the hemicellulose is the only component of wood that absorbs much moisture breaking it down improves the stability of the wood. High absorbed moisture in the wood adds some mass, and lowers the Young's modulus (stiffness), so it tends to drop the 'wood' resonant pitches and changes the sound. Moisture also adds damping. Thus well seasoned wood is likely be more stable in it's sound, as well as structurally.

Wood reaches equilibrium moisture content fairly quickly, so it's not necessary to keep wood you're going to work on in the stable shop atmosphere for a long time before you use it. Dead green freshly cut wood several inches thick can be dried to within 5% of EMC in six weeks if it's cut, stacked and stored correctly, and I've dried spruce for instruments that way without much drying degrade. Usually the advice is to allow one year of drying for every inch of thickness for cabinet stock, and I'd call that minimal seasoning.

[charles Tauber]

Originally Posted by Howard Klepper

The issue is not sound, Charles. It's stability...

Originally Posted by Alan Carruth

Since the hemicellulose is the only component of wood that absorbs much moisture breaking it down improves the stability of the wood... Thus well seasoned wood is likely be more stable in it's sound, as well as structurally.

Thanks for those corrections and additions.

[seangil]

Charles, Alan, Howard - thanks very much for this thread. I am taking away that its fine to store wood in my production/shop area, but there could be advantages to putting pieces that I won't be using for some time into an environment that fluctuates more. At the moment, I don't have an outdoor shed that I can use, but could store in my attic. Over the course of the seasons, that will expose the wood to a temperature range of 40-60 degrees. It will also expose it to VERY high humidity for a few months during the summer.

Should I be concerned about storing wood in a highly humid environment? It would be at least 60% RH and maybe even 70%. I assume that temperature would run into 90 degrees on a sustained basis with that humidity and maybe occasionally breaking 100 degrees.

Any thoughts on whether that environment would be negative? And if I put it into such an environment, then any precautions that I should follow?

For those interested, I saw a very compact set-up on this forum:

http://www.anzlf.com/viewtopic.php?t=465


Sean

[seangil]

To Charles' question on calibration...I used a salt solution/bag test to check reading at 75%. I'll look at the other link that you shared.

[Dyson Guitars]

I store all of my guitars sets in a shed where they get the full brunt of my NC summer and winters. They experience everything but the rain and moisture. I am a believer in seasoning wood this way. It has not led to structural problems with my builds at all that I can see. When I am thinking about building with a set it comes into my shop and gets all the temp/humidity controls I can give it for a while before I work it.

[redir]

Since you mentioned LMI they have a web page dedicated to this topic that you might want to look at:

https://www.lmii.com/blog/2017/10/07...g-and-storage/

"When you receive your wood, you want to store it so that it is not exposed to excess humidity and extreme fluctuations in temperature. In most climates a dehumidifier is a must during the summer months and a humidifier is used during the winter, or whenever intense heating is used (woods stoves especially) or moisture-robbing air conditioner units."

So they actually recommend against it. Of course violin makers have been doing this for centuries.

I don't normally use tops till they are many years old though I did build one with a Sitka top that I got from Alaska Specialty Woods about one month in my controlled shop. From ASW thought they have been seasoned in the rounds for sometimes decades.