Basics of humidity control - Info/FAQ

Gombessa · 2024-07-20T00:28:43+00:00

I thought I’d put some of the thoughts and learnings I’ve had on the topic of humidity control to paper, in the hopes that it benefits other piano owners/buy...

rogerch

Gombessa This right here. Very cold air holds more moisture, so if you have 15 "units" of moisture in the air, in cold air it would be only 10% RH because the air can absorb more, but in hot air it would be 80% RH, because relatively, the air is almost at saturation.

Hey Gombessa I think this is backwards. Warm air can hold more water than cool air. As temperature goes up, RH goes down if absolute humidity stays the same. At least that’s my understanding and it’s consistent with my observations where I live: as the outside temperature changes throughout the day the outside RH changes in the opposite direction.

Since you have studied humidity way more than I have I may have either misunderstood you or else I’m just wrong. What I wrote seems consistent with https://themachine.science/relative-humidity-and-temperature/

Gombessa

rogerch Hey Gombessa I think this is backwards. Warm air can hold more water than cool air. As temperature goes up, RH goes down if absolute humidity stays the same.

Ugh, yes you're right, I'm all in the middle of confusing myself. Warm air can hold MORE moisture than cold air, so RH goes down because it has now more capacity relative to what it could hold at a cooler temp. I have to go back and edit a few posts/responses to correct the record here 🙂

navindra

Rubens I live in Montreal, Canada

[OT]
Oh nice! Montreal is a beautiful city. I lived there for a decade. It's amazing. Pierre Marchand is not too far away and Esmonde White as well... would love a report on Oliver's pianos with the Fandrich action one of these days.
[/OT]

However, after a decade in Montreal, I could easily survive "winters" elsewhere in a t-shirt and shorts... I don't miss those -40 deg winters at all and it's not like the summers don't get hot either. I would have thought it would be hard to do optimal piano climate control under those Montreal conditions, but it sounds like you're doing just fine based on the other thread!

Rubens

navindra
Thanks! Yes, the only problem is that the missus is not too happy about me turning down the heat in winter and the AC in the summer. Very counterintuitive for normal people!

ShiroKuro

I’m glad I’m not the only one who is willing to suffer with a cold house in the winter to protect the piano! 😄

@iternabe another sign of high humidity might be sticking keys.

rogerch

This discussion made me curious so I moved my piano hygrometer outside and let it sit for a while.

The outside temperature was 100.9F, RH was 27% (Yes it is hot here! We have had an unusually hot summer!)
At the piano, the temperature was 77F, RH was 40%

I found a calculator that given a source temperature, source RH, and target temperature calculates the expected RH at the target temperature: https://www.markusweimar.de/en/humidity-calculator/

According to that calculator, cooling the outside air to 77F without changing the absolute humidity should result in relative humidity of 57%. That's 17% higher than the measurement that hygrometer took at the piano. From what I have learned today about air conditioners I suspect that 17% lower RH is due to condensation happening in the air conditioner. Somehow it all works out so that the RH at the piano is reasonable, and I'm fortunate that this is the case year round.

Thanks everyone educating me, this has been most interesting! 😀

Gombessa

Interesting find! I believe that being at home also contributes to a baseline RH increase indoors, too. If we aren’t home, the RH at my house stabilizes at around 40%, when we are back, even without a change in temp or climate control use, the RH typically rises (enough for the dehumidifier to kick in and bring it back down to 45%).

rogerch

Gombessa That makes sense! Humans are wet!

pseudonym58

I think I could easily drive myself crazy worrying about RH. I have had a Piano Saver device installed (on a Yamaha C2), I try to keep the temperature below 65° F during our cold, dry winters, and below 78° F (using central AC) during the hot humid summers in northeastern Connecticut.
I also have an ultrasonic humidifier (I try to clean it frequently) in the room with the piano, but I have my doubts as to its effectiveness.
The piano seems to hold its pitch well for a few months at a time, so hopefully it's okay.

Gombessa

pseudonym58 I think you're doing more than enough here 🙂 I definitely agree it's easy to get carried away. I certainly do, but mainly because I find it fun, and I'm interested in the data!

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