I was once tuning in the SC recital hall when an obvious malfunction occurred with the humidity control. I noticed it happen immediately, when I felt the cool humidity falling from overhead and smelled the odor of stale water that was released by the system. My hygrometer, laying on the plate of the piano started up from somewhere in the mid 40% range and within 15 minutes read over 70%. I checked the tuning I had already accomplished up to that point and realized it had begun changing so fast that continuing to tune was a waste of energy. I just quit where I was, packed up my tools and left because I knew it would change back as soon as the system reset and restabilized. Jeff ----- Original Message ----- From: "David Love" <davidlovepianos at comcast.net> To: <caut at ptg.org> Sent: Saturday, December 12, 2009 11:40 AM Subject: Re: [CAUT] temperature and pitch Are you suggesting that the moisture content of the wood of the piano changes in 20 minutes enough to influence the tuning? I don't think so. Otherwise the piano in my house would go out of tune every time I boil a pot of spaghetti. Very simple experiment. Take a wooden dowel and rub it along the string with just enough force and speed to heat up the string. See what happens to the pitch and then see what happens when it cools. Then, bring your hot plate into the room with the piano and boil a pot of water watching your hygrometer for a change in humidity. After one hour measure the pitch. David Love www.davidlovepianos.com I feel these two examples are due to humidity changes that corresponds to the temperature changes, rather than changes in the strings/plate. Certainly the strings and plate can be affected by temperature changes but I don't see that as a primary reason we see such a change in tuning stability with a 5° to 10° change in temperature. Joy! Elwood Elwood Doss, Jr., M.Mus.Ed., RPT Piano Technician/Technical Director Department of Music 355 Clement Hall The University of Tennessee at Martin Martin, TN 38238 731/881-1852 FAX: 731/881-7415 HOME: 731/587-5700 -----Original Message----- From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Fred Sturm Sent: Friday, December 11, 2009 10:50 PM To: caut at ptg.org Subject: Re: [CAUT] temperature and pitch On Dec 11, 2009, at 4:07 PM, David Love wrote: > Can't comment on the amount of change per unit of temperature but > the speed > with which it happens is fairly quick. Started tuning a piano in a > church > this morning with the temperature about 50 degrees at the start. > Pitch was > about 2-3 cents sharp in the tenor section. Tuning up from there by > the > time I got to C5 (20 minutes or so) the temperature had risen to 70 > with the > heat on and a remeasure of the tenor section showed that the pitch > was about > 2 cents flat--pretty uniformly. Steinway D. It does show that > there are > clearly two aspects to pitch swings. Temperature in which probably > the > metal parts are affected, and humidity in which the wooden parts are > affected. What I think my example shows is the whole thing, strings and plate, getting to the new temp and stabilizing there. Strings themselves move pretty fast, especially if there is a bit of air movement with either hot or cold air moving, or radiant heat (sun, stage lights). Some of that is bound to be happening if the temp is rising in a room by 20 degrees over 20 minutes. That is one thing. But another thing is the plate catching up with the temperature change, and possibly/probably counteracting the initial pitch change a bit. I am assuming that happened thoroughly overnight in my example, that plate and strings had plenty of time to come to a stable new temp. Not that this is some kind of definitive proof of anything. I just had the opportunity to take data from an experiment that happened without my needing to go to any effort. So I did so and documented it "for the record." One Steinway A under the conditions I described did what I described. Regards, Fred Sturm University of New Mexico fssturm at unm.edu
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