Is 35-40% humidity acceptable?

[yell03]

Originally Posted by L20A

We have a humidifier on our central heating system.
It only keeps the house at about 30% to 35% RH.
The furnace doesn't run all the time and the unit only adds humidity when it is running.

I added a room humidifier to our bedroom. My guitars are in a closet in that room.
That helped bring the humidity up to about 35% to 40%.
This is in Utah which is the second driest state in America.

After several years on nightly adding water to the humidifiers and replacing them about every other year, I gave up on them.

I have always used in case humidifiers and keep my guitars in their cases.
Some of my guitars are over 35 years old and show no signs of humidity related problems.

For me keeping the humidity constant is as or more important than keeping the humidity high.[50% to 60%]

I also have a whole house humidifier in my system and also only see 30-35%.

The guy who installed it told me there is a relay that you can add that will allow the humidifier to work by leaving the fan on even when the heat is not running.

I might do this.

For now, my acoustics are in their cases with sponge humidifiers and humidipacks.

In case is in between 40-50%.

Closer to 50 if I use two sponge humidifiers, closer to 40 if I use one.

[rokdog49]

Originally Posted by Bruce Sexauer

I typically build at 38%. Most guitars live in a wetter environment than that. I am quite comfortable with my work down to 30%, but lower is not such a good idea. Up to 65% does seem to do any harm. If a customer knows they are going to be outside that range, or are usually going to be at one extreme or the other, I can build drier or wetter, but not by more than about 5 to 8%.

Good enough for me and as I said in an earlier post, I think this humidification thing is overblown. One or two of my guitars reside in the consistent humidity
range of 35-40% for weeks at a time in the winter. I have had no shrinking fret boards and no other issues whatsoever.
Obviously, if it makes folks feel safer, opinions are just opinions.

[leew3]

As you've seen in this thread, anecdotal evidence trumps the recommendations of guitar builders. The manufacturers of each of my guitars recommends an average humidity of 50% so I take them at their word and use a room humidifier to keep them in that range. Doubtless others will disagree, that's the charm of an online forum.

[RustyAxe]

I find that to be ideal tonally (guitars seem to resonate a bit better), but usually keep my studio at 45-50% in the winter because "that's what yer s'posed to do".

[john57classic]

Originally Posted by RustyAxe

I find that to be ideal tonally (guitars seem to resonate a bit better)

I agree! More articulate as well to me.
With one possible exception, I think all of my steel strings sound their best in the 35-40% RH range. I don’t “target” that range, but I don’t take any action to correct upward either.

[mmasters]

I remember a prewar martin I had, 70 years old, one owner. It was scratched all over, beat to death, discolored and the finish was gone on most of the top. It was in Arkansas for all those years.

Here's the guitar
https://www.dreamguitars.com/shop/in...-00-21-00.html

Well, I doubt this guitar was ever humidified during the winter and not one single crack. Think about that, 70 winters un-humidified in Arkansas and not one crack. It was lightly built too.

Another thing I noticed about that guitar was it was built with good quartersawn woods. So if you have a guitar with good quartersawn woods I don't think you have to worry about 35% or possibly even 30% humidity.

[hdsteele]

Martin comments in their owners manual....
"Martin keeps the factory at a constant 45-55 percent humidity and 72-77 degrees Fahrenheit. If either humidity or temperature get far away from these factory conditions, your guitar is in danger."

Well fine. I live in South Florida and as high as the humidity gets outdoors the inside of my house is always 35%-40% and 75 degrees. Most times humidity is right at 38% but have seen it as low as 34%. For the past 6 years I have kept my Martin CSNY dreadnaught out on a stand away from windows/sunlight 24/7. No frets sprouting, no top sinking, nothing. Seems to be happy. Maybe I am just lucky. I will say that these levels are really consistent and never vary much for long.

[Earl49]

Consistency is key, even toward the lower end of the RH range. You are watching the key symptoms to catch it quickly if your guitar starts to react.
Wild swings up and down will hurt the guitar more than constant humidity at 35-37%. The factory limits are stated to protect the builder from warranty claims - it gives them a convenient "out". Slight variations really won't hurt anything generally.

[ljguitar]

Originally Posted by ld27

I just got a new acoustic guitar and I want to make sure it's being handled properly.
My hygrometer reads between 35 and 40% humidity.
I did not a get a case with the guitar. I have one on order but it is showing a 2 month wait. It's an Epiphone Masterbilt EF-500R.
I ordered a soundhole humidifier which will be delivered on Tuesday.

So my 2nd questions is how often should I use the humidifier. The guitar is almost always on a stand.

Thanks
Len

Hi Len

You will get radically diverse answers. Depends on which 'EXPERT' you 'ANOINT' as the master.

My guitars live between 35-40% and have for nearly 40 years. Never a crack nor a warp. My last guitar was built in a shop which was kept about 37% during the winter (because we have really low humidity in the winter in this part of the world).

When it gets below 35%, mine tend to go into cases.








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[CaptRedbeard]

35-40% RH has been right for me and my various types of guitars. When we moved to the high desert of Nevada we bought a large humidifier, set it on 40%, and just fill the water tank every few days. Even in the back bedroom, it stays about 37%. I really never paid much attention to RH and my guitars but never abused or treated them badly. One thing I consistently do is wipe them down and put them in a hard case when done playing. They all stay together in the office closet.

[lar]

Two more data points (as if you need more information):

Lowden: says the minimum is 45%!

And Larrivee:
https://www.larrivee.com/pdfs/Larriv...aintenance.pdf

[colder]

I try to keep mine around 50% but there’s no reason to panic if it’s 40%. Or even lower, if it’s a guitar that’s been properly humidified throughout its life and it’s just temporary. Yes cracks can happen but these are mostly due to protracted periods of neglect, like a guitar that goes a whole winter dry and under tension and is never attended to at all. If you’re losing sleep over it, put a trash bag over it with damp sponge or two in the bag, and tie it until your case comes.

As others have said, old timers will tell you that they never humidified their old guitars for many years and never saw cracks or parts of the guitar shriveling up to make the guitar look like it’s in a Picasso painting.

Do what you can and don’t worry too much, especially at 40%, nothing is going to happen

[JayBee1404]

I have Martins and Lowdens. Both CFM and GLG recommend 45-55% for their instruments, and that’s where I try to keep mine. During the winter, when the room RH Drops to the low 40s, into the cases they go with the humidifiers. In the summer, when room RH rises to the low 40s, out they come again.

It seems to me that it’s eminently sensible to follow builders’ recommendations where RH and their instruments are concerned.

The only time I’ve had a problem was when I left my Martin J-40 out on a stand during the winter with room humidity around 35%. The top sank to the point that the guitar buzzed all over the FB, fret-ends became ‘sharp’, and the finish was cracked around the body where the wood and binding met. Fortunately, our excellent local luthier told me what was wrong, and three or four weeks in its case with ‘sponge-in-a-baggie’ humidifiers, plus a fret-end dressing, put it back in to playable condition.

The usual disclaimers apply......IMHO, YMMV etc.

[hdsteele]

Realizing that 35%-40% is on the traditional low side of things I did go looking for a good hygrometer a few months ago to verify what my A/C system tells me. Went to a well known, respected, local guitar store/luthier. Asked the owner what he had in stock and he told me he didn't carry any at all. With the humidity down here there wasn't much interest in them and everyone keeps their inside humidity about the same, 35%-40%. Was sort of surprised at his comments. Again, well known shop, I believe the only luthier with a Plek machine on the east coast or at least use to be the only one. He said my 35%-40% was fine for my 4 electric and one acoustic guitars as it was a pretty stable environment. Just another take on things.

[jaymarsch]

As you can see, you are getting answers all over the place since no two situations are exactly alike in either the environment or the guitars. From the luthiers who built them, I know that two of my guitars were built in a shop at consistently controlled 38% relative humidity, while the other was constructed at a consistently controlled relative humidity of 45%. I own 5 hygrometers and keep them in the cases. I keep one in the room where my guitars are stored in their cases and one in the room where they are most often played. None of my hygrometers are more than 2% off from one another and they are measured against a hygrometer that has been calibrated. I have not had a problem at either a week of 65% humidity or a stretch of days of 32% humidity.

The secret to all of this is really to measure and then monitor as needed depending on seasonal changes. I was shipped a guitar from a drier environment and the fret ends were protruding and very sharp. No cracks in the wood yet but I knew I needed to hydrate the instrument slowly. Since my inside relative humidity was between 52% and 57% during those months, I left the guitar out of its case secured on a stand in my living room. It took 6 weeks for the guitar to regain enough moisture to bring the wood back even with the fret ends. So, time is also a factor in whether or not an instrument can be adversely affected to the point of no return. Sudden drastic changes in humidity and temperature can create their own issues.
I hope this information is helpful.

Best,
Jayne