Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Help - humidification causing rust on strings/pins?

Hi all,

Two years ago I bought a used ~2003 C. Bechstein 7 footer that we keep in a living room that is about 15x15. We had a large Dampp-Chaser installed on it. The first time we got it tuned, the technician said the Dampp-Chaser is not enough and since the living room has double doors, we should keep that closed and put in a humidifier to supplement. He tuned it in November of 2018 and despite having baseboard heating our hygrometer indicated during the winter that the humidity fell into the high teens and the piano fell out of tune and one of my hand made acoustic guitars actually saw the wood split (even though it was in its case the entire time). As a result, we purchased a Boneco S450 steam humidifier and have run that daily trying to keep a humidity of around 40% although there are times it is off for a few hours when it runs out of water and we don’t realize (it is off during the spring-early fall).

Here is the issue, over the past year I had noticed the humidifier has completely rusted the decorative nail heads of our couch in the room. And now I’ve noticed the strings and pins (i might be using the wrong term here, not the tuning pins but the other side of the piano that holds the strings in place) closer to the humidifier is rusted!!!! The decorative brass and main brass plate framework all looks fine. As does the metal bass bridge. And the strings closer to the keys and tuning pins near the keyboard is fine.

I assume the damage is done but not sure what to do? We have not had the piano tuned because of COVID. For now, I’ve closed the top board. I could move the humidifier but I don’t think there is any escaping this issue or it could end up rusting the parts closer to the keys. We have a hygrometer in other parts of the house and it measures 20%.

-What should we do for now?
-Is there a solution or something to try to rub on the strings? Or something to prevent further damage? When i ran a microfiber cloth across the strings lightly, rust residue rubbed onto the microfiber cloth.
-Can a technician fix this, is this going to require restringing the entire piano - again this is <20 years old? What would something like that cost?

Help and thanks in advance?

Here are some photos and on closer inspection the tuning pins are starting to show some slight tarnish and the strings are rusted there as well? I’m not sure what to do but have turned the humidifier off for now but I distinctively remember the piano falling out of tune when we didn’t run the humidifier which is why I purchased the humidifier.

[img]https://lightroom.adobe.com/shares/8daa8390b6cc40f2a6cf48e8c272701f[/img]

[img]https://lightroom.adobe.com/shares/028d041c8487483c9ff5f29e4b75d729[/img]

[img]https://lightroom.adobe.com/shares/c14de66c7779476f8eab52d1b234726b[/img]

Wow it's bad. You can clean strings from rust fairly easily but the point is that you can't really clean them where bearing points are without taking them off (and then you might just put a new set of strings), on agraffes, capobar, bridge, tuning pins, hitch pins and those are most important points. This piano would probably be very hard to tune in that state. I don't really understand how could this happened, humidity in this room must have been very high, even up to 100%, or maybe your humidifier was blowing moist air directly on your piano? (if it is that kind of humidifier)

You will see lots of debate about humidifiers on these forums.

The short version from my opinion and my opinion only: Dampp-Chaser is not enough. Steam humidifiers very bad. Wick good. Calibrate a hygrometer to measure RH. Never let the humidifier decide the RH. Try to keep it 40-42%, BUT BUT BUT your mileage may vary.

We had to lower humidity to 35% because in our new house 42% grows mold all over the doors and windows. I’m not worried about 35% + Dampp-Chaser hurting the piano. Huge wick humidifier with 4 gallons that I refill as my routine every morning.

Dehumidifier keeping in it 42% in the summer.

We do leave the top open all the time. Perhaps it is the steam humidifier. Our thought using the Boneco S450 was steam prevents mold. It is warm when it comes out of the humidifier but wouldn’t burn you at all. It was my understanding that this humidifier would also reduce white residue that comes out using the other humidifiers more prone to rust.

What humidifier should we use?
Should I keep the top closed for now?
Should I have the humidifier on for now?

We have the humidifier set to 40%. We have a digital hygrometer called sensor push and the follow shows the temperate and humidity for the last year. The humidifier is used during November to March and the doors are closed then. The rest of the year we leave the doors open to the foyer and don’t run anything.

[img]https://lightroom.adobe.com/shares/bed59d6e5b5345b79fdd4620bcbc4652[/img]

Humidity will cause mold, rust, etc.

The theory behind the steam version is that it is so hot that it kills any bacteria before shooting it out all over the room, likea child’s bedroom. I thought the steam ones cause the white residue, not prevent it.

Anyway, I’ve had a 3000sqft wick humidifier for ten years that’s been just great, aside from needing to adjust the output each time we move to a different house.

Your hygrometer... have you calibrated it, though? At least once a year. Google how to stick it in a bag with rice and all that.

Hmm. It appears that it’s the ultrasonic that leaves the residue. The wick is another option altogether. Boneco appears to have a high capacity hybrid one that uses this method so maybe I’ll buy it ($380). The wick ones I see online that are recommended are all only a gallon capacity like the Honeywell 350.

What is the brand of the wick humidifier you gave. I would love the idea of sticking a whole house humidifier in our foyer to power the whole house and not just that one room?

I have not calibrated the hygrometer as it’s this weird digital sensor. Will look into it. Thanks.

Looking at your data plot, there are long periods of time where the humidity is approaching 60% and the temperature is in the low 60s. When steel, like piano wires and hardware, gets cold it stays cold for a long time because it has a lot of mass. When warmer humid air meets that cold steel, moisture condenses and you get rust. Not sure where you live, but you need to get a dehumidifier to keep the humidity down below 50%, and less if possible depending on the outside temp and cost of energy, etc. It would help a lot to keep the lid closed and a cover on it. What you want to do is slow down the temperature/humidity changes inside the piano to try to prevent warm humid air from meeting cold steel.

I live in northern NJ and not by the shore or anything. We do not open the windows at all due to allergies. When the humidity is in the 60’s that in the August through October period where we do not run the humidifier but have our central air conditioning maintain about 69 degrees but may be colder in that room as it’s just a smaller room. Do you really think that is the culprit?

Here is what I’m wondering is the issue. First I have a steam humidifier. Second until this year we did not use distilled water but our well water which goes through a water softener. I don’t taste it but is it possible that the water is actually acting like sea salt and then because it’s steam it the condenses on the strings and causes it? I wonder if that is the issue and switching to a non steam but also non ultrasonic humidifier will not cause more issues?

I assume the damage is done here but maybe a technician can try to clean some of it off based on other threads I’ve seen on here. I may also consider restringing the whole thing but I assume we are talking $6k-$10k? I also don’t know that process at all. Would it be done in my house? Could it end up sounding different? Is there any risk during this process? And then I don’t want to do it and corrode it in another three years. When I received the piano 2.5 years ago it was in near mint condition despite being made in 2003 and within that time frame even with minimal usage and trying to follow the rules I’ve messed up the finish.

Mine is a 4DTS900. The reviews aren’t that great, but it’s been great for us for a long time. I believe the tanks are 2.5 gallons, two of them. I only need to fill it every day or every other day. If you put it by a return air duct, the furnace will suck it up and take care of your entire house. I go through two wick filters a season.

Calibrating a hygrometer usually doesn’t mean changing the display, as only the very high end ones let you do that. Instead, use the bag/water/rice method and note the difference displayed. Adjust your humidifier output accordingly. Most people over humidity their homes once they get their hands on a humidifier.

Shoot for 42-46% year round if you can. If you have guitars, too, they want 52%, so compromise.

Don’t overlook summer. You will probably want a dehumidifier, too. Hook it up to a drain so you don’t have to empty the tank every day.

Probably. It only takes a few times when moisture is condensed on the strings to initiate the rust process, you don't need to have unfavorable conditions for weeks or months. If you have central air conditioning you likely have forced air heat. Have you considered putting a humidifier on your furnace?

Salt does not evaporate with the water, it stays behind in the humidifier (assuming there is any salt in the water), so if you are concerned about salt in your water evaporating and then condensing on the strings, that can't happen. I think if your steam humidifier is close to the piano it might be contributing to the problem because it outputs warmer mist than different types of humidifiers. Hopefully you don't have it pointed right at the piano.

I think given the numbers on your data plot if you keep the piano closed and covered it will stop further rusting because your environment is not extreme, it's not like you're living in the jungle. I'm not a tech so I have no idea what to do about the existing problem, that's a very sad thing to happen to your piano.

I use a room evaporative humidifier, not a mist humidifier in the winter. I have a room dehumidifier for the summer months. If you are getting condensation in the winter months, that means you are pushing the RH% too high in relationship to the current conditions. Her in central Indiana, I never push the RH over 40% in the winter. Sometimes in the winter, I can't push it above 35% when we're having a polar vortex of temps below 10 degrees. I have my piano tuned after the season has shifted to cooler weather, the RH% has dropped, and the piano has settled for a couple of weeks. In the summer, I try to keep the RH around 50%, so the seasonal swings are minimized.

There are tools to clean the rust off of strings. I recommend talking to you technician about having that done ASAP.