Trying to make sense of all this... Ray, although I follow your argument, I don't think we can assume that a room or a house is a sealed container. Heated air, because of heightened molecular movement (of course you know this - allow me to babble) will require more volume at the same atmospheric pressure. Since we are not increasing atmospheric pressure (a sealed container), the excess air has to go somewhere (in an attempt to equalize) and leaves the room, house or whatever, taking whatever moisture it is holding with it. Conversely, as air is cooled (I know - not cooled, looses heat) does the lower volume requirement not draw air from outside the house and bring in with it whatever moisture it is holding? It would seem to me that this would be at least a partial explanation to why a piano will accept and lose moisture with movements in temperature. Total moisture will fluctuate as the air, and the moisture it is carrying, flows back and forth. Concerning the original question of temperature variations, I think we have missed an important issue (or maybe I wasn't paying attention). What happens to the strings and plate with the changes. We all know what happens to our tunings in a concert hall when the stage door is opened and the room temperature changes rapidly. These changes in our tunings can't possibly come from moisture concerns, as the effect is almost immediate. Or think of what happens in the middle of a tuning when the sun comes through the window and hits a portion of the strings. Whether the concern is temperature or moisture related, I wouldn't want my name on a tuning of a piano whose environment changes 10-12 degrees on a daily basis. At least not without some sort of disclaimer. Rick >> Sorry, guys. >> >> I've taught science too many years to accept that the relative humidity >> change has anything to do with the change in wood moisture content. >> Relative humidity changes as temperature changes, but the actual amount of >> moisture may indeed stay the same. I understand all about dew point, etc., >> but actual moisture content does not change because the relative humidity >> does UNLESS the temperature stays the same. >> >> A sealed container of air (or wood)may hold X amount of moisture. If it is >> heated, its relative humidity goes down, because it is capable of holding >> more moisture at a higher temperature. The converse is true upon cooling. >> True, wood being a solid, there is less difference caused by temperature >> than in air. But the content doesn't necessarily change with the relative >> humidity reading which depends upon the temperature at which the humidity >> reading is taken. >> >> Ray T. Bentley, RPT >> Alton, IL >> >> Ready to retire this spring after 37+ years of teaching. >> >> >> ----- Original Message ----- >> From: <vem@email.byu.edu> >> To: <caut@ptg.org> >> Sent: Tuesday, January 22, 2002 3:12 PM >> Subject: Re: Temp fluctuation affect? >> >> >>> No, but the wood moisture content would change (be higher with a lower >> heat and >>> lower with a higher heat) because of the relative humidity change. >>> >>> - It's true that lowering the temp will decrease the relative humidity >>> - reading, but it will NOT mean that more moisture is present. Relative >>> - humidity is just that...relative! The absolute amount of moisture >> present >>> - will not change solely by lowering the temperature. >>> - >>> - >>> - -- >>> - Ray T. Bentley, RPT >>> - Alton, IL >>> - ray@bentley.net >>> - www.ray.bentley.net >>> - >>> >>> vince mrykalo >>> >>> >>> >> > > ------------------- > Brent Fischer > Senior Piano Technician > Arizona State University > > > _____________ Rick Florence Piano Technician Arizona State University, School of Music
This PTG archive page provided courtesy of Moy Piano Service, LLC