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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Seems like you need a bigger humidifier. Just a thought.


Hello Mike,

Actually to be honest I don't have a humidifier. This is just the unaltered reading I get. Thanks for your reply.


I have three hygrometers. They all indicate different relative humidity. The expensive analogue "Airguide" reads around 40%, digital "Diamond Crown" from eBay reads 34%. An inexpensive analogue purchased from a cigar shop reads 29%. When I used a very accurate sling psychrometer, it indicated the RH was 40%. I would suggest you chech your hygrometer for accuracy before you pump gallons of water into the air. I am in No. CA valley and rarely need to increase the RH but when I do, I use a hot plate and a tea kettle. Or I invite my lawyer friends over and ask them questions about ethics.

Allen, I would suggest boing to the nearest Drug Store and purchasing a $20 digital hygrometer so you can at least have a vague idea what your humidity level is.

 Most of us deal with this problem as an individual room dictates. For instance, when I took over my 1000sf shop in the basement of an industrial building, I knew I was in it for the long haul, so I made some permanent and some temporary solutions. It was forced air heating. I sealed/blocked the intake vent, then sealed up both rooms with caulking, doing all the ceilings and floors, installing door seals/weather proofing , (*inside doors I am talking about) , bought my own heaters  (two Kenmore portable oil filled rads)  and did everything I could to seal this shop so I could control the humidity. I then bought the first in a long line of humidifiers

My humidity in the shop (as in most forced air buildings without any humidification) was at 27% before. Now I keep it at 50%. 

If you are not doing serious repairs were wood storage and solid wood instruments are being affected, I am not sure I would worry too much. You should defiantly  search out what a humidity starved guitar looks like also, so you can see exactly what all those symptoms look like. The list is not all that long, but with 30% humidity, I would make it my business to  to know.

 In my case, I think I was down about 2k for all the renos/finishing/sealing my shop. Your situation may just require buying a humidifier. I hope this helps.  

It was the cheap $20 hygrometer I purchased that indicated the RH was 29% when it was actually 40%. Depending on the temperature of your shop (that is why RH is relative) and the size of your shop, you would need to evaporate a lot of water to get from 29 to 40% RH. If the added moisture is not needed you may be creating more of a problem than a solution. Please let me know what drug store sells hygrometers, I have never seen one there.

Up Canada way, they are in every single one Harrison. And we could easily start a thread about how notoriously inaccurate the digital hygrometers are. Sometimes they are bang on. My current one reads about 5% low, but the last one was accurate. It has to do with the calibration at the factory, and the sea level were they are at I have read on the beauteous Collings Forum. 

Well - never been to a Canadian pharmacy but apparently they all think I need Viagra cause they email all day about it. RH is important in guitar building and repair but also important for proper hydration of humans, kudos to our brothers and sisters to the north for stocking RH monitors in pharmacies, down here they tend to focus on candy and booze.

Hey thanks Harrison. My neighbor right across the street is a lawyer. I never thought of that.


Digital hygrometers are inherently inaccurate and even if we find one that is pretty accurate in the range that we care about (40 - 50%RH) they can be way off in slightly higher or lower ranges.

I use a psychro-dyne which is basically a powered wet bulb to check the RH and then twice a year or so use the results to calibrate my wall hanging Abbeon hygrometer so that I have a reading at a glance when need be.

Wet bulbs are pretty accurate but one also has to understand that RH readings can be impacted by many things such as our own breath when testing.  So multiple readings is what I use and then I average them.  I find that I have to make slight changes to my mechanical Abbeon as frequently as a couple of times annually.

When we were learning about RH in a Lutherie shop we took it pretty far and tested every hygrometer that we could find.

The results of our testing were very telling with the conclusion being that many of the digitals on the market today are glaringly off and off enough to cause problems with what we do.

Wood moves, an understatement, and countless builders who have not taken steps to either humidify or dehumidify as required have paid the price in cracked tops, potato chipped plates, and more.  Most new builder discussions concentrate on what bandsaw to purchase, the meaning of grain spacing on tops, using a mold or no....  What I always suggest to new builders is that job one is to deal with what ever one needs to do to have a stable, acceptable RH range in your building environment.  Then you can purchase the mother of all bandsaws.... ;)

By the way not only do we humans benefit from the very same RH range that most factories use for guitar building (40 - 50%RH) your tools including power tools will benefit by not rusting.  All of my stuff that lives in my RH controlled space looks like new and I am not the biggest on waxing tables either so this is helpful.

My hats off to ya Allen for asking about RH.  It's not a gnats ass by any means or at least it isn't to the builder who I know who invested over 200 hours in his first gutiar only to be rudely awakened at 3:00AM one morning by a loud crack heard from his basement.  His first guitar that had been sprayed with the final coats of finish the day before decided to ventilate itself and do so in a rather dramatic manner.  The gutiar split down the front....

Lastly if one has any aspirations at all to ever sell their creations RH is even more important in terms of limiting the potential liability associated with a warranty claim.  One of the reasons why the pre-war Martins are so very iconic in the minds of many is that back then Martin was not as keen to have an understanding of the associated liability with having to honor warranty claims.

It's also why over the years Martins have been built heavier, thicker, etc.  We can still build on the light side but if one ignores the potential issues of not addressing RH, using well seasoned materials, one may be learning far more about gutiar repair sooner than they may have ever planned to do so.

I applaud Hesh's research and his generous willingness to share his knowledge on this subject.  Hesh, good work, you've given us all a lot to think about.  

Allen, don't be deterred by the complexity of the subject and related solutions.  At the very least, buy a digital hygrometer and strive to keep the humidity at 50% and the temperature around 70 degrees.  

I have a 400 square foot shop.  It takes two of the large consumer grade humidifiers that they sell at sears to keep this space humidified during the driest months.  I find that I have to change the filters every 3 months or so for the units to operate efficiently.

Keeping my shop at or close to 50% rh and 70 degrees year round is a must for me.  If a guitar has too much or too little moisture, I can't do any repairs except a little set up work.  I always get a guitar back to 50% (which can take a couple of weeks, even with a little help from a dampit) before I do any repairs that involve permanently changing guitar's geometry: refrets and neck resets are a couple of common examples that come to mind.

 Holy !!! Hesh, how much trouble was all of THAT!!! Hats off to you for that amazing post!   

Hesh is the Gold Standard for me. 


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