[CAUT] Reading low humidity (was seasonal SB failure)

[Greg Newell]

Accurate reading have always been somewhat of a 
concern to me but the question I keep coming back 
to is "Does it really matter how much relative 
humidity is in the air or should we be more 
concerned about the moisture content in the 
wood?" I'm somewhat familiar with using the 
charts and determining the moisture content based 
on how long the wood has been in the specific 
environment, etc. but I wonder if soundboards, 
specifically, are holding true to that equation 
since their also coated wood. Seems like that 
would have some effect. I don't know how to 
factor that in other than to take a moisture 
content reading from the wood directly. Perhaps 
this has all been covered before and just hasn't 
sunk in yet.    .......wouldn't be the first time.

best,
Greg


At 09:35 AM 3/2/2006, you wrote:
>This thread seems to be heading in all sorts of directions. Heading
>back to low humidity, and what that does to tonal production, I have
>been puzzling recently over how to measure low humidities accurately.
>I have a sling psychrometer, but I have found that the lowest
>readings I can get with it are in the 18 - 20% range. I am thinking
>this is the limit of the particular instrument: that there is only so
>much evaporation that will take place from the wick, it only holds so
>much water, there are limits to how many calories that will be
>extracted to to the change of phase from liquid to vapor, something
>along those lines.
>         It is bone dry here, no rain since November (well, we had a trace
>last night). My Air-guide hydro-thermo (similar to Radio Shack) has
>been reading 11 - 15% consistently as it sits in the music building.
>My Mannix (the grey one, about $80 from Pianotek, with a bulb on the
>top, that reads to tenths of percent/degree) has been down to 3% in
>one location, and under 10% consistently in many. Another indication
>is frost on the windshield. There hasn't been any, with overnight
>lows of 20F on average. Meaning dew point is below 20F. Pretty dry.
>Under those conditions, I thought the psychro would read lower, but
>no, 18%.
>         So I'm wondering if anyone has thoughts about accurate measurement
>of humidity below 15%. I guess a dew point devise would work, where
>you lower the temp of a reflective surface (eg, polished stainless
>steel), and at the point where it begins to cloud over, that temp is
>the dew point (by definition). Not something I can make, and probably
>quite expensive to purchase. How do these electronic devises work?
>How accurate are they really? How much do they change in calibration
>over time?
>Regards,
>Fred Sturm
>University of New Mexico
>fssturm@unm.edu
>
>
>
>_______________________________________________
>caut list info: https://www.moypiano.com/resources/#archives

Greg Newell
Greg's piano Forté
mailto:gnewell@ameritech.net