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Thread: Humidity?

  1. #1

    Default Humidity?

    Hi, all, first post here. I have a Martin D-28 that I put a soundhole humidifier in during the heating season to keep it from cracking. I also have an F-style mandolin that was custom built for me. I have had it for 11 years and have never done anything to protect it from low humidity. It has never cracked. 1) Why should this be? 2) Should I be doing something to humidify it? Thanks.

  2. #2
    Registered User John Bertotti's Avatar
    Join Date
    Oct 2002

    Default Re: Humidity?

    Not knowing where you live I can say I keep humidifiers of some sort in all my instruments or cases or both. My house is already down to 25% humidity. Over the summer my house might get into the 40s or even hit 50 but only for a few weeks to a. Month before it starts creeping down again. I have set up all the instruments at about 35-40% so I don’t need to do much of any tweaking on guitar neck relief as seasons change. Neither of my mandolins have adjustable necks but and old bowl back of mine started to have some neck wiggle until I humidified it in the case. Oasis in tue sound hole and a sponge ona. Soap container with holes up by the headstock. Worked great but I check the case humidity routinely and keep it around 40%.

    It is cheap insurance get a case hygrometer and keep it in tue zone. I think that is much better than rolling the dice it won’t be an issue.
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  3. #3
    Registered User Mandobart's Avatar
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    Apr 2009
    Washington State

    Default Re: Humidity?

    Relative humidity and its effect on musical instruments is something most people don't grasp. Part of my mechanical engineering degree studies involved a good bit of HVAC, ASHRAE tables and such.

    Absolute humidity is the total amount of water vapor in the air. Relative humidity is the ratio of the actual amount of water vapor in the air to the maximum amount it can hold for the current temperature and pressure. Whenever people discuss humidity on an instrument forum they're talking about relative humidity (RH).

    There are multiple factors that determine if a particular instrument will suffer any permanent damage from excessively low RH, incuding the wood used, how the wood was dried, construction methods, how fast the temperature/RH are allowed to change,etc.

    I grew up in northern NM, where winter time RH can often be in single digits (temperature too). I'd never heard of humidifiers then, and my violin and guitar survived just fine. So did my dad's 1940's Martin classical guitar and my grandfather's 1880's violin.

    Since then I've heard multiple horror stories from others whose instruments suffered catastrophic damage under much milder conditions.

    I now keep my instruments hanging out on the wall in a temperature and humidity controlled music room at home. I still take them out to jams, gigs, festivals, camping trips too.

    The only instrument of mine with cracks is my old Applause guitar that went to sea with me on submarines when I was in the navy.

    Those guitar soundhole sponges do no good for an instrument not in its case, and even then don't do anything for the neck, headstock or fretboard.

    The first step is getting a decent hygrometer so you know what the RH is where you store your instruments. The next step is deciding how much time, money and effort you want to spend trying to control it.

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  5. #4

    Default Re: Humidity?

    Pretty much one would have to have a lot of information, most of which can’t be measured, to predict the cracking potential of even two very similar instruments, so those who have expensive ones, which are necessarily frail, tend to get obsessive about the subject. The major way a thin panel will crack is if its edges are rigidly constrained so that tension builds as the panel dries out. In other woodworking, you make a panel float in a frame expressly to prevent that, but as has been said, instruments violate most traditional woodworking rules. So, if a panel is, say, arched, it might be able to avoid cracking by changing shape, or if the rim (sides) of an instrument have a little compliance, or the glue, better survival might be expected. What the bowl on a bowl back does is complex, but I have a bunch of them that have survived crack free for more than a century with certainly no seasonal humidity constancy. Then too, instruments have braces, often cross-grain that presumably do not change length while the panel expands and contracts. Does one brace pattern cause cracking, or prevent it?
    Manufacturers, in the early 20th century, flocked to plywood as the best way to minimize some problems, including weakness of thin solid wood panels, but these days, the knowledgeable folks prefer the weak, expensive material so much that it’s the key word in marketing a mandolin. That, and desire for fancy-grained backs and sides, which are themselves unpredictable and often fragile.

  6. #5

    Default Re: Humidity?

    I'm in NH and usually run a dehumidifier in the summer and humidifier in the winter. A few nice guitars not interested in cracks or bridges lifting. Without those appliances the humidity can get up to the mid-60's and an low as mid 30's humidity percentage.

  7. #6
    Registered User darylcrisp's Avatar
    Join Date
    Oct 2010
    Banner, Ky

    Default Re: Humidity?

    this is a nice, accurate hygrometer to place in a room where your instruments are-if you attempt to keep a humidity level around 40-45% your body and your instruments are more happy.

    this hygrometer does not need batteries or plugged in btw.

    here is a case hygrometer that is decently accurate-does need a battery:


  8. #7

    Default Re: Humidity?

    Chicago is hard on guitars in the winter. I keep a couple of evaporative Airdog humidifiers running 24/7 in my condo to keep humidity above 40%. If you have a prized instrument, keep it in the case with a wet sponge in a small drilled out Tupperware box. I’m thinking that arch top instruments may be less susceptible to cracking than flat tops, but humidity is good for your instruments, prevents viruses from traveling in the air as effectively and prevents that Winter Zombie skin look. Do it. 40 and up.

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