how much does humidity matter?

[dan in va]

A few new guitars that had to be babied with humidifiers drove me to buy only older instruments or new ones that were built under dry conditions and needed no humidification. This notion can limit choices a whole lot, so i'm asking for your experience about new cracks forming under winter conditions. i live in the central/western part of VA, near the Blue Ridge mountains and have forced air heat.

It seems the mandola i like the most at the moment is built in a shop that keeps humidity at 45%. Is it true that after a few years of age a mandolin won't need to be humidified in my situation?

Under what situations have your mandolins cracked from dry air? And will mandolins built at 45% humidity need a humidifier forever?

[sunburst]

Instruments need to be built with wood that is somewhere around 8% moisture and the RH where they are kept needs to be maintained between 40% and 50% as nearly as possible for the life of the instrument. Wood is hygroscopic, it will take on moisture when the RH is high and it will give off moisture when the RH is low, forever. If an instrument is built with wood with a moisture content that is too high (green or wet lumber) it will probably be problematic. If it is built with wood that is drier than about 6% moisture, the wood will gain moisture until it is at equilibrium with the air (unless you're in Phoenix or someplace with very dry air) and the wood will swell and that can be problematic. Furthermore, when conditions are dry it will once again loose moisture and shrink, and can crack. There's no getting around the fact that wood moves and we have to control the RH where our instruments are stored, or else take chances with them cracking.

[michaelcj]

John is spot on in his description of what happens to wood during humidity shifts. And that it is most critical during the building phase goes with out saying.

There is something that does make me go HUmmmmm though when I read the myriad of threads on any acoustic instrument forum regarding humidity and instruments.

What did we do before we had the internet?

How did those factories in Kalamazoo and Nazareth deal with the issue in 1850 or 1936? How did Woody Guthrie deal with the issue hauling his Gibsons from LA to Bakersfield, to Grand Coulee? What were Bill and the Boys thinking on the road with the gear in the trunk?

And how did any of the As and Fs, the 28s, 45s, 18s, Jumbos and Ls survive to be so prized today?

To be sure some were treated better than others but there are a lot of survivors that never knew central heating let alone a special humidity controlled room or a Heritage case.

I've been playing since the 50s repairing since the 60's. I remember potato and apple wedges in cases,.... when the first damp-it came out.... and those first silica gel packets, but those early, prized instruments may have seen a potato or two but precious little else.

Now I'm not suggesting that it shouldn't be a consideration, or storing them in the yard in October is a great idea...... but I wonder if we haven't gotten just a bit OCD about the whole thing.

Just things that make me go HUmmmm..... glad Woody and Bill didn't seem to mind all that much.

Mike J

[Michael Lewis]

Laminated (plywood) instruments are far less prone to having humidity issues.

[Bertram Henze]

What did we do before we had the internet?

How did those factories in Kalamazoo and Nazareth deal with the issue in 1850 or 1936? How did Woody Guthrie deal with the issue hauling his Gibsons from LA to Bakersfield, to Grand Coulee? What were Bill and the Boys thinking on the road with the gear in the trunk?

The dangerous thing is not humidity as such, it is the change. To avoid change, you can do two things:
- only play at home, with the instrument in much the same room all it's life, being played sometime.
- play the instrument a lot, two hours daily at least, and your hands, your whole steaming body will provide a natural humidifier.

[David Houchens]

My idea of building in 45, percent humidity, or as close as I can, is its middle of the road and allows movement in both directions to an extent without trouble. If I built in moist conditions for a buyer in a moist climate, all might be great until they sell it to someone in a dry climate. Then I am the one asked to warranty it or get the bad name.
I don't know how some of the older abused instruments I've worked on have survived the conditions they've been kept in, but I've had to repair plenty that haven't faired so well.
When an instrument comes to my shop with a crack to be fixed, the first thing I do is set it on a stand in my shop for several days. If that crack closes up, on its own, I can pretty well guess it lives in a dry place.

[stevedenver]

My two cents.

Moderation in conditions and changes, IMHO, is the key. I can only report my observations of my guitars and mandos over the past 40+ years, here in Colorado. I don't humidify. I don't have forced air. I am mindful, of temp, and storage and treating them like a living being in terms of comfort ranges mentioned.

First and foremost, wood up until the 70s, possibly later, was properly seasoned, dried over MANY years. To my limited knowledge, currently only smaller builders , and then only some, buy wood and let it sit for two to three years in their own storage before building. This isn't the way larger production factories can practically work. I presume one cannot have hundreds of thousands of dollars of wood sitting for years seasoning, as was once the practice.

I have no idea if kiln dried is truly the equivalent, negating my thoughts and theory, but TIME, without fail, seems to reveal if a tree is willing to conform to instrument form, or 'decide' to warp, crack, etc. I tend to buy instruments two to three years after construction, simply because most wood issues will have surfaced by this time. There may be no foundation to this, but following this ....I have had no post purchase issues.

Second, rapid changes, I think, are a real issue. That is why, if left in a regular old case, when not being played, the case acts as a buffer between dry and humid days, creating a less drastic mean, and less rapid absorption or drying.



Otoh, perhaps where I live is simply around 40-50% on average.

After seeing the Taylor video on how their guitars react to excessive dryness, IM really glad I don't have to deal with that. A close friend has a Collings D-42 style, which also suffered a disasterous top crack shortly after leaving the factory-(had to be re-topped). I don't draw any conclusion, but, it appears that some of the modern tech woodworking aspects don't allow a great margin or error for natural variations in humidity.

I agree that playing daily will likely provide the 'mean' I speak about. I don think body moisture has anything to do with a finished (lacquered etc) instruments moisture or absorption, except possibly, the fretboard at best, unless one plays in a body bag, LOL.

[bratsche]

Here where I live, 40% would be close to as dry as it gets - with a dehumidifier on almost constantly.

My instruments must all live in a perpetual state of swollenness, as the room they're in fluctuates only between about 65% and 70% throughout the year. It would likely be higher than that if we left the windows open and didn't turn on the air conditioning (which is only doable in wintertime anyway, or when there's no choice during power outages!)

But they're evidently all happy, as I never have any issues with them. I guess it's because there's hardly any change.

bratsche

[dan in va]

There's a notion out there that maybe over time the cells don't absorb humidity as much, which might be a trait of older wood behavior. Taylor guitars were mentioned, and my experience with them wasn't good and i'll not have another...unless it's from that special run that were braced and sounded like Martins, and a friend has a Dan Crary model that's exceptional, too.

[sunburst]

There's a notion out there that maybe over time the cells don't absorb humidity as much, which might be a trait of older wood behavior.

That notion may exist, but as far as I know, there is scant evidence to support such a notion.

[buchrob]

I am a Canadian snowbird who spends the winter in Arizona, almost NO humidity at all and the summer in Quebec (wet and damp all spring and fall, tapering off to horribly humid in mi-summer).

For years I have brought instruments back and forth and have had no problems because I observe the "moderation in all things" philosophy mentioned above. The killer is having drastic changes over a short period of time, especially with instruments made of materials that act differently. Carry your gear in the trunk of your car in a Canadian winter and then go play in an over-heated, sweaty venue is for sure a recipe for disaster.

For instruments left in Arizona over the summer (humidity up and down, temperatures from 60 to over 110 degrees) as well as those left behind in Canada when the heat gets cranked down in my unoccupied house: they get stored in foam-lined gig bags at the end of the season then sandwiched between a (not too heavy) mattress and a bedspring. This arrangement acts as a giant insulating buffer that eliminates drastic temperature and humidity changes.

When transporting, I avoid the airlines like the plague, and always ship what I can't carry-on via USPS ground. If you've ever put a tetra-pack (square vacuum pack) of coffee in your airline luggage, you will instantly see what I mean at the end of your trip.

I have never had a problem.

[John Flynn]

What I've learned is that humidity is never a problem...until it is. And when it is, there has already been some damage. I have three small builder mandolins. Two of them are 12 years old, one is 8 years old. I have worked really hard to keep them humidified, using house, room and case humidifiers, as well as calibrated hygrometers. Still, the treble side of the top recently sank on one of them. The luthier who worked on it said he thought it was a humidity issue. He raised the top back up and installed a new brace. This caused issues that then required two major setups to resolve. The instrument plays and sounds great now, maybe better than it ever has, but it has given me a healthy respect for humidity.

[bratsche]

If you've ever put a tetra-pack (square vacuum pack) of coffee in your airline luggage, you will instantly see what I mean at the end of your trip.

Never done it, nor am likely to, as I no longer fly. So please, don't keep us hanging. What happens?

bratsche

[buchrob]

Never done it, nor am likely to, as I no longer fly. So please, don't keep us hanging. What happens?

bratsche

Apparently the vacuum (or lack of air pressure) in the cargo bay is greater than that used to seal the packages. They will come out even more compressed into an irregular brick. You may have the same shrivelling experience with packets of powdered sauce mix.

[Bertram Henze]

Apparently the vacuum (or lack of air pressure) in the cargo bay is greater than that used to seal the packages. They will come out even more compressed into an irregular brick. You may have the same shrivelling experience with packets of powdered sauce mix.

I guess they expand during the flight, allowing the contents to shift, and recompress upon landing.
I guess that would not be a problem for instruments - but the cold in the hold could be.

[Paul Hostetter]

Usually the hold shares the same everything that the passenger cabin has: temperature, air pressure, etc. Otherwise there would be a lot of dead dogs and cats. I don't seem to hear much about that.

[Paul Busman]

I'm with MichaelCJ-- I think life is too short to fret (no pun intended) too much about humidity. I've owned wooden stringed instruments since the early '60s. I live in the Northeast where summers are hot and muggy, and where indoor conditions with forced air or hot water baseboard heat get mighty dry. In our current home, for example, the spaces between the planks of our hardwood floors swell shut during the summer, but gap as much as 1/16 inch in the winter due to humidity changes.
In all this time I've NEVER humidified an instrument and NEVER had an instrument crack or had a seam separate. My old Guild F-30, which I bought with funds from my very first paying job in 1966 has the expected wear and tear of an instrument well played and enjoyed, but absolutely no humidity related damage. I think that worrying too much about my instruments would really detract from the pleasure I derive from them. Dunno who said it, but "worry is the interest you pay on a loan you may not even owe".