To Avery Todd, thank you for thinking of Dampp-chaser relative to harpsichords and humidity. Let me add just a bit to what Gayle passed on this morning and yes, please forward it to the harpsichord list. RH goes up when the temperature drops. There has to be some other factor affecting the environment to make it go down. The phenomina is that the air has the capability to hold moisture at the reduced ( or dropping) temperature. A cloud forms or fog sets in for the most part not because of a change in moisture content of the air but because the temperature has dropped to dew point. This is the temperature at which the air cannot continue to hold the amount of water present and therefore starts to come out in the form of visible water vapor. I suspect that in Mr. Feeser's situation the hygrometer he was sing to measure RH did not wrk very well. Without going into a long disertation about hygrometers, let me say that they become terribly inaccurate if not "excercised" periodically. Klaus Fenner does a very good job of explaining this phenomina in the July 1993 ( I think) PT Journal. If anyone would like a copy of this please call me on 1-800-438-1524. If Mr. Feeser's RH was 35% at 68 degrees F, the psychometric chart tells us it would be 82% at 45 degrees F, and certainly this wouldn't be considered "dry". On the other hand, if his hygrometer was current, the 45 F/ 32% RH would yield a very dry 15% RH at 68 degrees F as Bud Finc points out. While temperature is important in itself and its effect on string length, it's most significant import comes from its influence on relative humidity. What we have found in so far unpublished test results is that temperatures effect on tuning is moderate and immediate, while humidity' s effect ( caused by temperature change) is significantly more severe and begins to take place several hours after the temperature change. Far more information on hygrometers and psychrometers let me provide the following. Radio Shack handles a small electronic hygrometer that sells for about $25.00. From what I've seen of this, it's reasonably accurate. The problem is long form reliability. A film will develop on the sensor in about a year and its accuracy gets into the questionable area. Comfort Staation is handled by Piano Climate Control at 800-443-7509 and PianoTek at 800-347-3854 for the same price or perhaps slightly less. For long term reliability but somewhat harder to use, is a sling psychrometer available from Abbeon Cal Inc. My choice is model # 10-140. It was priced in my somewhat old catalog for $41.90 with replacement wicks (socks) at $4.00 for 12. This will provide good long term accuracy. Either one will put you in the ball park. To get better than ball park will cost a lot of money and it simply isn't worth it for general humidity measurements. Thanks again, Bob Mair
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