Rapid humidity changes?

[weldon7]

This may be a no-brainer, but I was wondering if folks could enlighten me on which course of action is better. I live in an apartment that only has a window A/C unit in the bedroom. During the day, my wife and I leave the A/C off and the humidity in the apartment gets up to ~55%-60%. At night, we turn on the A/C, and humidity falls to around 40%-45% with the A/C running all night.

My issue is that I had the mandolin in the bedroom in the winter, where we run a humidifier to keep the humidity >35%. I never thought about moving it come summer. I noticed yesterday a fair number of very thin cracks in the fretboard. They're only visible at a certain angle and quite close up, but they're there. So, for the summer, would it be better to move the mando to the living room? The humidity is 50%-60%, but there wouldn't be nightly fluctuations with A/C. Thanks!

[sunburst]

More stable humidity is probably best, but we're not talking extremes here. If you're staying under 60% and over 35% throughout the year, that's pretty easy on the instrument compared to playing by a traveling musician in places like Atlanta in the summer, Phoenix in the summer, Seattle in the winter, Portland in the winter, that sort of thing.
Keep in mind that it takes a while for the moisture content of the wood to reach equilibrium with the air, so daily changes in RH in your home result in more subtle changes in moisture content of the wood in the instrument. I think of a rapid humidity change as a situation like carrying your mandolin from your air conditioned hotel room to the middle of the festival grounds and opening the case in the 90% RH.

[allenhopkins]

What wood is your fingerboard made of? John's spot-on regarding humidity levels; the conventional wisdom is that instruments are made and function best around 50% humidity, but fluctuations 15% on either side of that shouldn't damage an instrument. You may notice some tuning fluctuations, the mandolin going sharp with higher humidity and wood expansion, but no damage.

Some woods do show a bit of grain separation when exposed to dryness, but that shouldn't happen in the humidity range you describe. Some woods do have half-hairline separations along grain lines, which are basically stable and not a real concern. Keep an eye on the separations, change humidity (and temperature) as gradually as possible, and if you notice other changes, a visit to a pro repair shop might be in order.

[paulspafford]

I just bought an Eastman mandolin back in the winter. It's my first instrument that was expensive enough for me to worry about these things. The guy at the store recommended leaving it in my case whenever I'm not playing it, and buying a case humidifier.

It's not as nice as having it out where you can easily grab it and just play, but it takes all those worries about humidity away.

[EdHanrahan]

I'd worry more about the quick changes of temperature than of just simple humidity. A good friend kept his Martin guitar on a stand in his bedroom (that is, out of the case), and did like you: A/C at night (to REALLY cold, like 60 or 65), and then, thanks to full sunlight, high 80s or more during the day. (Old house, marginal insulation). When the top seem separated, Martin denied the warranty coverage.

[weldon7]

The fretboard is made of rosewood. I've put the mandolin in the living room, so as not to expose it to rapid temperature and humidity changes every night. The cracks are pretty small, and I'm just monitoring them for now. Thanks for all the responses!

What wood is your fingerboard made of? John's spot-on regarding humidity levels; the conventional wisdom is that instruments are made and function best around 50% humidity, but fluctuations 15% on either side of that shouldn't damage an instrument. You may notice some tuning fluctuations, the mandolin going sharp with higher humidity and wood expansion, but no damage.

Some woods do show a bit of grain separation when exposed to dryness, but that shouldn't happen in the humidity range you describe. Some woods do have half-hairline separations along grain lines, which are basically stable and not a real concern. Keep an eye on the separations, change humidity (and temperature) as gradually as possible, and if you notice other changes, a visit to a pro repair shop might be in order.

[Boomslang]

Just wanted to concur on three major points that were referenced, that I've found most significant, in my experiences. Rapid temperture changes are "rapid", opposed to humidity fluctuations, which play havoc more insideously, and manifest in their distruction over time. Having related that generality, leave your mando in the car here in Maricopa County AZ., when it is ohhhhhh, say 112, (outside the car), and just see how rapid temperture changes can redesign your favorite sound box. Wherever you are, 5% humidity of AZ or soaking wet at the NY Island, leave your mandolin in that trusty hardshell when your not enjoying it; Tends to help with humidity and temp peaks and valleys in the short term. In the arid climate where I live, I use "2" Oasis humidfiers in the case with a hygrometer. I'm usually at 55/57%.

[jaycat]

I'd worry more about the quick changes of temperature than of just simple humidity. A good friend kept his Martin guitar on a stand in his bedroom (that is, out of the case), and did like you: A/C at night (to REALLY cold, like 60 or 65), and then, thanks to full sunlight, high 80s or more during the day. (Old house, marginal insulation). When the top seem separated, Martin denied the warranty coverage.

Was the top seam separated, or did the seam just seem separated? If a seam only seems separated, they'll never honor the warranty.

[weldon7]

How do you all put oil on your fretboard when you polish it? I was thinking of just running a Q-tip with some lemon oil on it under the strings, but wasn't sure if that would work. Do you all just wait until you're changing strings anyhow?

[Tim2723]

I've done it that way (but with a bit of paper towel). Don't over oil.