Question about strings going sharp

[Ellen T]

I had to lay off playing for three or four weeks due to hand pain, and when I got my mandolin out the other day, all the strings were pretty significantly sharp. I could understand strings going flat during a non-play period of time, just from the tension causing a slow unwind, but I just do not understand the physics or whatever that would cause a dormant instrument to go sharp.

If it's relevant, the weather has been mostly humid but all over the place in terms of temperature, so during the time I didn't play, we had the heat on, we had the A/C on (both of which would reduce humidity), and we had neither on and the windows open (which would increase it). I do keep a homemade humidifier in the case but admit to being a little lazy about keeping it damp at all times.

I'm just curious about what causes strings to tighten on their own. For all I know, the Fret Fairy was upset with me because she also caused my pick container to go flying when I picked it up and I still can't find all of them.

[Charlieshafer]

Humidity does indeed cause strings to tighten up, as the wood top expands ever so slightly. On large instruments, like my cello, it can go very wonky after just a couple of days, going from dry to humid. It's all in wood expansion, nothing to do with the metal strings themselves.

[pheffernan]

If it's relevant, the weather has been mostly humid

It's relevant. In my experience, increased humidity leads a mandolin to go sharp.

[multidon]

This happens to my instruments quite often. Especially my hammered dulcimer.

If you brought your strings up to pitch at a certain temperature, then the instruments gets cooler, the strings would contract a bit then tension goes up and there is the sharpness. It wouldn't take much. Just the normal variability of the room temperature is enough.

Another theory. If your case is very air tight and you tune your instrument with the heat on then put it away, the case would act as an insulator to the heated room air and so it would cool down in its case. Same result.

I think it is a product of temperature variation and does not have anything to do with relative humidity. Just my opinion.

[Tobin]

I get it all the time. Higher humidity or colder temperature will do it. In your case it's probably humidity. Even if you're not playing for more than a few days, you should still open up the case and check that it hasn't gone too sharp in there, which of course increases stress on the instrument.

Sensitive little things, they are...

[Phil Goodson]

What Charlie said. Happens at my house almost every day.

[Ellen T]

Thanks to all, even for the slightly contradictory answers. I'll know next time I have to leave the poor thing in its cage that I still need to open it up and tickle it under the chin to keep it healthy.

[Nashville]

yep, when it rains here my tuning will go sharp. even though my windows are closed. odd. very noticeable.

[Larry Simonson]

What I have seen over the past 5 to 8 years or more is that all three of my mandolins go sharp while setting in the case after a day or two during the warmer months and go flat in the colder months. It is happening again this year. I am pretty convinced that this is a result of the water content in the air. Warm air at some % humidity holds more water than cold air at that same humidity. Thus waters partial pressure is greater in warmer air for a given relative humidity.

The good news is that tuning is easier in the winter as one only has to bring it up to pitch. The bad news is that tuning in the summer means you have to flatten all strings and then bring them up to pitch.

[Ellen T]

The good news is that tuning is easier in the winter as one only has to bring it up to pitch. The bad news is that tuning in the summer means you have to flatten all strings and then bring them up to pitch.

Yes, that really is a nuisance and made me think, for the first time, that I might get an electric tuner. I've been using a pitchpipe for almost fifty years, but I think I am less patient than I used to be. My hearing is still excellent but it's possible there is some nuance loss, so it just might be taking a little longer to tune than it used to.

[Ivan Kelsall]

From Tobin - " Higher humidity or colder temperature will do it." I get exactly the same thing caused by low temps. During the winter months my mandolins will go sharp from one day to the next,in the summer they go flat,& it's been that way since i began playing 9 + years ago. I accept it for what it is & just tune 'em up (down !),
Ivan

[Mandoplumb]

Something we have to put-up with. When all I had was cheep overbuilt plywood mandolins I don't remember that being a issue, weather. Didn't seem to affect them, guess we could go back to those. NOT ! ! !

[Carl Robin]

Yes, that really is a nuisance and made me think, for the first time, that I might get an electric tuner. I've been using a pitchpipe for almost fifty years, but I think I am less patient than I used to be. My hearing is still excellent but it's possible there is some nuance loss, so it just might be taking a little longer to tune than it used to.

It's possible to tune with pitch pipes, or a tuning fork, but SO much quicker with an electronic tuner, and in a noisy environment, the only way--for me at least. I love my "Boss TU-88" with an additional clip on mic on the bridge. It makes a satisfying beep when the string is tuned perfectly. It's surprising to hear that mandolins go sharp with increased humidity. Cooler temperatures obviously will, but I've had mine go mysteriously sharp too. Live and learn.

[sblock]

If you play indoors in a heated home whose temperature is fairly stable, then it's not the temperature making your strings go sharp. It's in increase in the humidity. Wood swells as it absorbs more moisture, making the neck longer at the same string tension. So the string goes sharp. Yes, strings can also go sharp in colder temperatures, as some have already noted, but I don't think that's what's going on in your case, unless you allow your house temperature to fluctuate significantly. Playing outdoors is another matter...

[catmandu2]

This happens to my instruments quite often. Especially my hammered dulcimer.

My HDs are somewhat affected, but not dramatically - as they're quite sturdily built. As on a piano - the strings are fixed at each end by heavy maple pin blocks.

Harp is a bear in this regard - one end is fixed in a heavy (bridge arm) block, while the other end inserts directly into the sound board of a light and lively gigantic box of wood; tuning is a constant.

[Stacey Morris]

When all I had was cheep overbuilt plywood mandolins I don't remember that being a issue, weather. Didn't seem to affect them, guess we could go back to those. NOT ! ! !

Weather affects my cheap mandolin . When I got it out last night after not playing it for 2 or 3 days, it was sharp on all the strings. I do have a electronic tuner, which I really like.

[Carl Robin]

My HDs are somewhat affected, but not dramatically - as they're quite sturdily built. As on a piano - the strings are fixed at each end by heavy maple pin blocks.

Harp is a bear in this regard - one end is fixed in a heavy (bridge arm) block, while the other end inserts directly into the sound board of a light and lively gigantic box of wood; tuning is a constant.

My harp strings go flat with increased humidity, quite reliably. Because the "box" relaxes with higher humidity, and the sound board gets a "belly"--the harp maker's term. Wood is also known to swell, with moisture. It's interesting that the differing geometry of the instruments causes the opposite effect: mandolin sharp, harp flat.

[Ellen T]

This is all so interesting to someone like me, who has enjoyed playing for decades but never got into the technical stuff. It's good to still learn!