Hi Guys,

I know that many luthiers try to maintain 40-50% humidity in their workshop. Mine seems to hover between 30 and 35%. Any suggestions on how I can increase the humidity or am I sweating over a gnats ass.

 Thanks guys. I always enjoy visiting the site. I never fail to learn something.


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Hey nathan how can you tell the moisture content of an instrument. If your space is the RH you desire and someone brings a guitar in for repair that dosent know what RH he keeps his instruments in how do you know what you need to let sit or what you can work on immediatly

Thank you everyone for your input. Building guitars is just a hobby for me now. However I have some wood stored for when I get serious so I appreciate your comments. I live in Eastern Washington  for whatever that is worth. If I lived on the coast maybe I would have a different problem. Thanks again for the input.


Thanks guys - there is a lot more to share on RH and our studies of hygrometers but I've already spent my quota for being long winded today.... ;)

Luke I'm not Nathan but if you don't mind I'd like to share a bit about how we know that we are dealing with a dry guitar and as such how long it may need to sit in the penalty box until it stabilizes.

Dry guitars have visual indicators at times, not always..., such as sharp fret ends being proud of the neck.  Come to think of it some new guitars leave the f*ctories this way so this is simply one thing to look for.  Strings being too low to play or sitting on the frets in the acoustic world are telling of a guitar that has dried out to the point that the dome of the top has reduced or collapsed hence lowering the bridge, saddle, and consequently the strings.  A sunken area in front of the bridge is telling too.

Cracks are also telling when they resulted from no known trauma such as someone sitting on the thing.  Don't laugh we have two in at the moment that were sat on.....

One of the rules of thumb for acclimating an instrument to one's environment is the old inch a year thing.  If the wood is an inch think it can take a year for the wood to acclimate.  Of course with our thin tops and backs, sides too a couple weeks is usually sufficient.

Last week I had an Epiphone with strings sitting on the frets.  I had set it up in the summer past and it had action of 4/64ths" and 6/64ths" at the 12th when I was done with it.  The owner lives in a college dorm with no humidification and forced air heating here in beautiful Michigan.  When it first started misbehaving and started buzzing I advised the owner to get a case humidifier and actually use it....  That was not enough however and this guitar became unplayable.

Recently, in the past two years we have seen far more dimensional instability in some guitars than we have seen prior.  We have a theory that in the struggles of these producers of goods that folks use disposable income to acquire, guitars, and during the great recession.... some factories likely did not invest in futures to the degree that they should have.

More specifically if one is in the business of producing guitars, especially acoustic guitars with thin plates, one knows from experience that the wood that they purchase today likely should be earmarked for production 3 - 5 years out, 5 is better.  Perhaps in the recent recessionary climate where guitar sales dropped off the map.... and producers were struggling just like everyone else the investment in wood for future guitars fell short?

We can't know but we keep seeing one model from a well known manufacturer where the instruments built recently are cracking far easier than they should.  Green wood?  Perhaps - that's our hunch.

By the way one of the methods that I use and was taught to rehumidify a guitar is to bag the sucker...  Use a large sponge such as what one might use to wash their car saturated and placed in the bottom of a "Hefty" garbage bag.  Lower the guitar into the bag, don't let it ever touch the sponge or any drops of water, tape it off at the top of the body and hang it and a day later any crack that has not been left open for too long likely will close as the wood expands.  Once closed the crack can be repaired but just like Nathan's example there is no point in attempting the repair until the instrument is rehumidified.

This is crack season for us here in Michigan.  We still see the usual someone sat on it, my ex shot it with a shot gun, stuff too but many, many more cracked instruments this time of year.

One thing that you never, never want to happen is have a shop dry enough to damage someone's instrument.  So we jump through hoops to get the RH thing down in an effort to subscribe to that old do no harm thing.

Back to Allen and in reference to Nathans very good point - if I am making this sound complicated my apologies.  It's need not be.  Simply get a hygrometer, check it against an accurate standard which one can make for less than $15 with the purchase of two lap thermometers, and then do what it takes to get your shop in the range. 

I tend to obsess over the RH thing because I tend to obsess over everything.... ;)  It is important but need not be difficult to obtain accurate and meaningful readings when one needs to.

So that gnats ass remains important but what I should have added was that it's not difficult most of the time to deal with.

Thanks Hesh. That makes total sense. It sounds like mostly experience, an acurate instrument history and daily living schedule is the key to determining how dry a guitar is. How do you keep the guitar off the sponge in the bag.

Luke my friend a typical 55 gal. trash bag is big enough to tie off at the neck joint while still leaving the sponge far enough below the instrument so that it's not touching.  I use masking tape to close the bag at the neck joint and it works very well.

If the crack is recent and caused by the gutiar drying out usually a day (24 hours) in the bag and then the cracks are closed and perfect for manipulating them back open with our hands and rubbing some glue in there.  This is also why, yet another reason why humidifying our shops can be important in so much as if my shop was say 30% RH even a freshly glued crack is back on the move as the guitar shrinks in the dryness. 

The nightmare would be to have a crack-free instrument crack while it's in our charge....  We are supposed to know better.....

Hey Luke, 

Hesh already gave you some really good answers to your questions, probably articulated better than my explanation.  But, FWIW:

The Symptoms:

Flat tops will have concave tops, concave necks and really low action when they are dried out.  The reverse is true when they have taken on lots of moisture in the summer.

Electrics and acoustics can develop twisted necks and "fret sprout" when they get too dry.  Necks can also twist if they get too humid.

The RH in a customers home:

Most customers have no idea what the rh is actually like in their home (and for people who ship their guitars here, I have no idea what the humidity is like in their state) so I don't bother to ask and I only give them a lecture about humidity if their guitar is really badly dried out (or in rare cases, dangerously humid).  

How I deal with mild and suspected cases:

If I suspect a guitar needs to stabilize in the shop's temp and rh controlled environment I'll add a week or more to the turn around and leave the gutiar laying on a bench or hanging on the wall until I'm ready to work on it.  

I just about always adjust a truss rod when a customer drops off the guitar.  In the summer or winter I will usually see a little movement after the guitar has been hanging on the wall for a week or so.  If it's only moved a little, then I'm good to go.  If it has moved a lot then I let it sit in the shop right up until the deadline, then I do the repairs at the last minute (or keep it longer if need be).

Obvious Cases:

If I know a guitar is dried out or over-humidified I add 2 weeks to the turn around.  If I know it's dry then I put a dampit or two in the case with the guitar and refill the dampits every couple of days until the guitar looks fine (this usually takes one to two weeks).  I then hang the guitar on the wall for a few days to be sure I didn't over or under humidify in the case.  

I am ultimately relying on the shop's continual temp and rh control to stabilize the guitars before any serious work is done. 


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