In my experience, pianos should be kept between about 35% and 60% RH. Below 35%, glue joints often break from wood shrinkage; above 60% you start to get mold on hammers and condensation on metal parts. The highest I've measured is 75%, and there were drops of water on the tuning pins and plate! Within these extremes, control within about a 10% range is ideal. With the DC systems, you can choose various "set points" for the humidistat. Standard is 42%, "wet" is 52%, "dry" is 39%. For new pianos in NM, I choose a "dry" humidistat to match our climate, and so that the customer doesn't have to fill the water tank so often. If a piano is older and is used to a normal or wet climate, I pick the corresponding humidistat to ease the stress on the piano. Dampp-Chaser has done a lot of research on this; you can call them for technical reports. I've got some pictures on my Facebook page (see below) of humidity damage. The first thing I notice is tuning instability, typically in octave 6 or above (OK, the first thing I notice is soundboard cracks!). I'll find small gaps at the base of bridge pins, where the strings have moved them sideways. A little CA stabilizes the pins. If left untreated, those gaps become cracks, which can merge in the top notes where the bridge pins all line up. Worse than soundboard cracks are broken glue joints: jack support posts in uprights, jacks themselves ungluing, etc. And of course loss of adequate pin torque is the real killer. Cracked ivories due to keystick movement, warped keys and keyslips, heck, humidity can damage just about everything except casters! --Cy-- Cy Shuster, RPT Albuquerque, NM www.shusterpiano.com http://www.facebook.com/shusterpiano On Jun 17, 2010, at 4:49 AM, Leslie Bartlett wrote: > Thanks for responses about humidity, specifically regarding issues > with the Baldwin I mentioned. Now I’ve another question for which > I’d appreciate help. The same church has a Shigeru Kawai, and two > Estonia grands. There was a major issue with tuning pin torque on > one Estonia, which has been resolved, but Mr. Josh Foust raised > another issue. He was fairly strong in his assertion that humidity > be kept between 50-57% for the Estonias. This can only be managed > with DC units, as they have AC running in the major music centers of > the church at all times and it is running in low-to-mid 60%. > > My question(s) regard humidity in general. If humidity levels are > maintained at a consistent level “x”, how crucial that they be kept > at a particular “x”? How does that significantly affect things > like integrity of pinblock and bridge pin holes being damaged by > expanding/contracting of metal against wood? Is there any general > consensus about how much the piano’s life will be shortened because > of humidity caused wood deterioration either by crushing fibers, > leaving looser tuning pins, and/or cracks in bridges? > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100617/f78e6dc5/attachment.htm>
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