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Thread: Why is Low humidity a problem?

  1. #1
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    Default Why is Low humidity a problem?

    Hi everyone,

    I am pretty new at this and I notice many humidity threads but I haven’t seen the answer to why Low humidity is bad for your instrument. Can someone answer this for me please? I recently purchased a Campanella Duo and would like to know if the low humidity could damage it.

    I live in western PA and noticed that the gauge in the case has been reading low since the temperature has dropped.

    Thank you, Doug

  2. #2
    Registered User Ranald's Avatar
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    Default Re: Why is Low humidity a problem?

    In a nutshell, it dries out your instrument, causing cracks and breaking the glue. If you Google "Mandolin Cafe humidity", you'll find a great deal on this topic.
    Robert Johnson's mother, describing blues musicians:
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    Registered User Doug Brock's Avatar
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    Default Re: Why is Low humidity a problem?

    Lots of good info online about humidity effects on wooden instruments. Here’s one article from Taylor guitars: https://blog.taylorguitars.com/using...-humidity-tips

    Bottom line - low humidity causes wood to shrink, which can cause cracks and other damage. High humidity causes wood to swell, which can also cause cracks and other damage.
    Doug Brock
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    Registered User Tom Wright's Avatar
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    Default Re: Why is Low humidity a problem?

    Arched instruments especially are sensitive to humidity causing dimensional change. This should not be a problem if everything shrinks or expands equally. In lractice I find all modern instruments are ok with low humidity, and only rapid change might be a worry.

    Old violins, by which I mean a couple hundred years, not those Gibson youngsters, will typically have a history of repairs for cracks and breaks. Those wil expand or contract differentiallly, risking new cracks, so owners of old fiddles try to maintain a given humidity. My modern viola was pretty much bulletproof but sounded unhappy in high humidity. An earlier modern instrument tended to come apart in soggy weather, due to that maker's belief in using very little glue.

    My modern flat top mandolins have thrived in humidity readings from low teens (S. California) to high 90s in high heat (Delaware beaches). The only effect humidity changes have on them is they go sharp in wet air and flat in dry air.

    If your instrument is not an antique or five-figure-priced modern archtop pay no attention to humidity readings.
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  5. #5
    Mando accumulator allenhopkins's Avatar
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    Default Re: Why is Low humidity a problem?

    I would cautiously disagree with Tom's post above. A too-dry environment causes wood cells to lose moisture and shrink; thin-cut, straight-grained wood (as in the top of your Campanella) can split along grain lines, since the entire top can't contract –– being glued to the sides -- and the inter-cell strains caused by the shrinkage may pull the cells apart.

    Dryness over a long period of time can also affect glue joints, but top (especially) cracks are the most common damage, back cracks next. The Taylor Guitars work sheet on the subject gives a good explanation and steps to diagnose damage; it applies, of course, directly to guitars, but I've recommended it for mandolin owners as well.
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    Registered User sunburst's Avatar
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    Default Re: Why is Low humidity a problem?

    If you feel like an academic exercise or two, first research the gas laws ("physics 101") and then research the hygroscopic nature of wood (best, understandable explanation that I know of is in the book Understanding Wood by R. Bruce Hoadley). If you understand those things you will then understand what happens to your instrument with changes in relative humidity, and why.

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    Registered User Louise NM's Avatar
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    Default Re: Why is Low humidity a problem?

    Different species of wood expand and contract at different rates as humidity changes. With a spruce top, maple back and sides, ebony or other super dense wood for the fingerboard, all glued together into one object, there are lots of stresses. Particularly if humidity changes quickly, something has to give.

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    Registered User bradlaird's Avatar
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    Default Re: Why is Low humidity a problem?

    Ditto to what sunburst said. And I am in the camp that sudden changes create the most havoc.

    For my complete diatribe on the subject you may enjoy this episode of my podcast:

    Grass Talk Radio 138 - Humidity

    http://www.bradleylaird.com/podcast/...how-notes.html

  12. #9
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    Default Re: Why is Low humidity a problem?

    Tom Ellis has an interesting perspective on this on his site (and nods to the sudden changes being more of the issue):

    Your mandolin was built at a humidity of 45%, please be cautious in the winter and do not leave it out of the case. Purchase a room humidifier, not a case humidifier. I personally think its better for the mandolin to be generally a little stressed (not less than 35%) all winter than to live comfortably at 50% and be taken out and shocked at a 15% humidity jam.
    From the bottom of https://ellismandolins.com/faq_warranty/
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  13. #10
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    Default Re: Why is Low humidity a problem?

    In addition to cracks as outlined, fret ends can poke out the sides as the fretboard contracts without them. I bought a Taylor guitar long ago that had been sitting in a fairly heavily A/C'd store here in NC (where we're usually reasonably humid, even on most winter days). After I got it home I noticed the slightest hint of a finish crack just beside the next on the bass side. My initial thought was to return it, but the store was a trek for me, and I really like the guitar. Took it to the local Martin Certified Luthier (who initially said, "Yeah, I've heard of those guitars" with a smirk, then later admitted he owned a nylon string Taylor, lol), who immediately told me, "Your guitar is slowly dying, man, you've got to humidify!" After some set up work and a week in his humidified shop, the aforementioned crack was no longer visible or palpable. Played that thing for over ten years before small bodied GAS took hold...

    I now have a whole house humidifier on my central heat/air, which I only have to run in the winter time when it gets into the 30-40s at night, but it's so much easier than dealing with as many case humidifiers as I'd have to juggle, even after my downsize 2 years ago.
    Chuck

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  15. #11

    Default Re: Why is Low humidity a problem?

    Quote Originally Posted by allenhopkins View Post
    I would cautiously disagree with Tom's post above. A too-dry environment causes wood cells to lose moisture and shrink; thin-cut, straight-grained wood (as in the top of your Campanella) can split along grain lines, since the entire top can't contract –– being glued to the sides -- and the inter-cell strains caused by the shrinkage may pull the cells apart.

    Dryness over a long period of time can also affect glue joints, but top (especially) cracks are the most common damage, back cracks next. The Taylor Guitars work sheet on the subject gives a good explanation and steps to diagnose damage; it applies, of course, directly to guitars, but I've recommended it for mandolin owners as well.
    That's a good read and fits my thoughts on humidity problems exactly. Some folks get it backwards. Even a well know shop owner in my area has it backwards. Don't quite now how he got such a good rep. Oh well.
    Richard Hutchings

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  17. #12
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    Default Re: Why is Low humidity a problem?

    (Probably in the Taylor write-ups that I read 8-10 years ago, but ...)

    I'm particularly annoyed by drying necks shrinking, mostly across the grain; that can leave sharp fret-ends hanging out to snag fingers, where there had previously been only smoothness. Last winter, I stone-ground the edges of a '30s European guitar's super-hard frets (files were n.g.), waiting for seasonal dryness to extend the frets to max.
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  18. #13

    Default Re: Why is Low humidity a problem?

    I have a friend (guitar player) who got a large crack in a great guitar due to low humidity. We get prolonged periods where it is well below 40 relative humidity.

    Back in my guitar days I observed a badly swollen top in constant 70 relative humidity (it was a Taylor).

    Since then I have tried to keep between 40 and 60 relative humidity in my home, which is what Taylor recommends, I figure it will work for all instruments.

    I moved from the damp place, where I had to dehumidify the home to keep it below 60, to the desert (where I met my guitar friend), where I have to humidify in winter to keep it above 40.

    It's 41 in my place right now... Almost yellow alert. :-)

    I have way too many instruments to fiddle with case humidifiers...

    I do like carbon fiber though, it avoids these problems.
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