Is 35-40% humidity acceptable?

[Herb Hunter]

I consider 35 to 40 % too low for my guitars. First, in that range, I can feel the frets beginning to protrude from the fretboard. Second, hygrometers are less accurate at the low range and the actual relative humidity could be lower than the instrument indicates. Third, too little humidity is worse than too much so it is better to err on the high side. I keep my guitars in the 44 to 52 % range. Fourth, if I'm maintaining a 47 % average during the winter and loose power for an extended time (as during and after an ice storm when humidity can reach the single digits), it will be a longer time before the humidity becomes critically low than if I were maintaining a level between 35 and 40 %.

[devellis]

Originally Posted by PWoolson

What warranty claims would those be? EVERY builder that I know has an exclusion for humidity for their instrument.

Paul -- You'll note I said warranty claims and not warranty repairs. Even if builders aren't on the hook for fixing problems, I'm sure they're happier if problems never occur and customers never need to contact them about issues. Also, I was suggesting what the actual RH should be, not what a hygrometer should read. But I take your point and I agree that being closer to an ideal 45% nominal RH provides a measure of assurance. I hope my comment didn't come across as suggesting anything critical about builders. that wasn't my intent. There are good reasons for them to make conservative recommendations (as you do when you caution people about hygrometer errors). I don't think they're "pulling a fast one," or in any sense acting against their clients' best interests by doing so at all.

Regarding hygrometer calibration, there is also the problem that errors from the nominal reading are not linear along the range of RH values. So, calibrating it to be correct at high humidity levels (as the salt method does) doesn't by any means guarantee that it will be accurate when the RH is, say 40%. In fact, I wonder if calibrating near one extreme (high end) of the RH range actually has an adverse impact on accuracy at the other (low) end, where errors are more critical. This is just speculation, though, and someone may have actual data that prove me wrong. Just thinking out loud here.

[deja]

Originally Posted by devellis

Regarding hygrometer calibration, there is also the problem that errors from the nominal reading are not linear along the range of RH values. So, calibrating it to be correct at high humidity levels (as the salt method does) doesn't by any means guarantee that it will be accurate when the RH is, say 40%. In fact, I wonder if calibrating near one extreme (high end) of the RH range actually has an adverse impact on accuracy at the other (low) end, where errors are more critical. This is just speculation, though, and someone may have actual data that prove me wrong. Just thinking out loud here.

I use a self-made psychrometer (wet bulb) to gauge how far off my cheap $12.00 hygrometer is. At lower levels between 37% to 45% my hygrometer is consistently off by 5%. At higher RH levels (around 50% or higher) my hygrometer can be off by as much as 10%. So, yes, it's definitely not a liner relationship.

[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%.

[MojoFelix]

I am posting this in case it helps someone.

I have 8 acoustics, some very very expensive, some not. Where I live, the relative humidity is often in the single digits. Keeping them in their cases cuts down on my playing time. When they are accessible, I play more.

I read about a player who happened upon a cabinet with glass doors and he put his acoustics inside on stands and he put a big sponge in in a bowl of water in there and a hygrometer and he had RH of about 50% all the time.

Noticing that I have a fairly large armoire in my room, I took out all the clothes and put my six-guitar stand in there along with two bowls with shallow water and medium size cellulose sponges.

I found could fit 2 parlors and 2 OMs in there. I put a digital hygrometer in there and I put a small cheap fan electric blowing on one of the sponge bowls. The RH in there is always around 50% and if it sometimes tends high (57%), I can regulate by just turning off the fan for a bit and that lowers the RH to the high 40s.

It is much easier than fiddling with the many widgets needed to humidify multiple guitar cases. Really all I do it pour a coup of water in the fanned bowl every morning and read the hygrometer when I happily open the door and just grab a guitar and play!

I also have an evaporative humidifier in the room (600 square feet), but that is more for me than the guitars, but I am sure it does not hurt the guitars when I have them out for playing. With the humidifier running the RH in the room reads 42% while the RH outside is less than 10%.

[Samogitian]

I have 3 different hygrometers (consistent readings within 1% margin) and maintain my apartment at 50% give or take all year round with aircon/dehumidifier and humidifier.

Something important probably not all people know - 50% humidity is not only recommended for guitars, it also happens to be ideal humidity for humans, so I would maintain it even if I didn't have a guitar.

[Von Beerhofen]

It helps when you understand your local weather patterns, i.e. how outside humidity can change in various seasons. Some people live in areas where the weather stays relatively much the same for long periods of time, I on the other hand live in Holland near the coast and weather can fluctuate greatly. Both in winter and summer indoor Rh can fluctuate between 25 and 70 here, with summers usually a bit more steady if the weather stays nice.

You can't humidify one moment not knowing if Rh will climb to extremes, or vice versa. Adding humidity overnight when the weather may change to top peaks is more dangerous to me then waiting for a change in the weather.
Here sometimes it just lasts a few hours and then things clear up again.

One moment it's dry, the other it's abnormally humid. Since I know it will probably change in a few hours I just watch how it devellops, and if I see it lasts more then a day I will know my guitars have had an impact from it and I can take counter measures knowing that the guitar will need something extra to ballance things out. Even when the weather changes around I might give it a bit too much in a situation where the guitar just had too little but it won't do much harm in 8 hours.

It's a kind of after the fact type of humidifying, because there is no other way I can see, other then perhaps installing airco or like some put things in an airtight chamber, which probably wouldn't work here anyway. So most of the time I do nothing, except for monitoring humidity.

As I said, being aware of what the weather will do with your humidity levels in any given season will allow you to more or less forecast that behaviour by just looking at the sky and seeing clouds roll in or out.

Here temperatures behave the same too, up and down with most extreme peaks during summer. If you change your indoor temperature for whatever period, you will influence Rh accordingly even if the outside weather hasn't changed. However if it did change then your guitars may be in an extreme Rh for that time.

It's not something to worry about since 8 hours may not necessarily cause problems, but understanding how things work is just as essential as monitoring the weather and knowing what the forecast will bring. It will give you better control. I.e. I know what is coming on forehand for the next few days and I know it's nothing that should worry me.

Ludwig

[rokdog49]

I'm going to get thrown under the bus for saying this but to me unless the humidity is consistently below 35%, this humidifying a guitar thing with all these devices you have to buy is a money making racket to me.

I repeat "to me."

[jpd]

Originally Posted by harmonics101

For my peace of mind, 35 to 40 percent relative humidity is definitely in the acceptable range.

I would be more concerned with sudden large fluctuations in humidity than the actual value per se.

35 to 40 percent RH and keeping your guitars cased when not being played keeps me asleep at night !

Guitars sound pretty darn good at that humidity level as well !

Harmonics101

+1...

[DCCougar]

Originally Posted by Les Tension

....After this I cut a small dish washing sponge in half, soak it, then wring it out as much as possible-put it in the baggie, put it inside the guitar and fuggetiboutit. "Till the sponge is dry. Rinse and repeat.
I'm in Colorado... pretty dry.....

That's what I use, too. Oh wait - inside the guitar? No, I put it inside the case, and I don't wring it out all that much. Not dripping, of course, but I leave quite a bit of moisture in that sponge.

Yeah, very dry here in the Wild West. Hygrometers in the cases show a bit less than 40%, even with bagged sponges in the cases. This isn't ideal, but my guitars aren't shriveling up. I think it's a sudden change in temp or the guitar's environment that you've got to look out for.

[Judson]

I forgot to refill the tank on my room huidifier last night. Went to bed with a very comfortable 45% and woke up to a disturbing 27% !!

Ouch!

No visible damage upon close inspection, but I now have two room humidifiers pumping away and I'm back to 40% and climbing.

I hang my guitars on the wall and I've never had a problem as long as I keep the humidifier running.

Living in central North Carolina, we don't have terribly dry weather, but we're in the midst of a cold snap and with forced air gas heat, it's worse than normal right now.

For me, 45% is the sweet spot. I'd love to have that year-round. Unfortunately in the summer, I have to fight to keep it below 60% ...

[kaos]

Originally Posted by Judson

I forgot to refill the tank on my room huidifier last night. Went to bed with a very comfortable 45% and woke up to a disturbing 27% !!

No worries, I don't think your tops will crack at 27% for one night.

[Earl49]

Just my opinion -- worth the price you paid: For an older well-seasoned guitar, 35% is on the edge but not immediately deadly. My house drifts down there from time to time, then I start humidifying them in their cases. I would not let a newer guitar go below 40% for very long -- more than a day. Felix, the glass-doored case with dampened sponges inside is a good idea, just an extension of a humidified case.

We also need an award for the first zombie thread of 2018.
The OP and main activity was from NOV 2010!

[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%]

[mercy]

A factor I dont see but in Bruce Sexauer's post is that it depends a lot on what RH your guitar was built at. I have mine built at 40% so if it goes down to 30 its no problem. If your guitar was built at 50% then 30 would be a problem. One thing on Burce's post, thank you Bruce for your willingness to add knowledge to our guesswork, that isnt correct but which I think he just left out a letter is that 65% doesnt hurt a guitar. Ive added the t to his post.