Temp fluctuation affect?

[Michael Jorgensen]

Hi Ray,
     You are correct that changing the temperature does not reduce the actual
amount of water chemically held in the air.  But the amount of water held
chemically is not what we feel.  Relative humidity  (RH) is what is felt and
what affects wood etc.  It is essentially the % of saturation.
     Lowering temperature increases RH.  The dew point is that temperature where
there is complete saturation or 100% RH.  Lowering the temperature beyond the
dew point results in condensation, removing actual water out of the air, and
also releases latent heat.  A dehumidifier coil cools air past the dew point so
water is removed from the air.   A heating rod or "dehumidifier bar" simply
heats the air in the piano, thereby lowering relative humidity.  Latent heat is
stored energy in the chemical process of evaporation, which is released upon
condensation.   It cannot be felt until it is released by condensation.   Like
latent heat, actual amount of water in the air is not measured, as it is held
chemically.  It can be calculated though using RH, temperature, and dew point.
     The higher the dew point is, the more moisture is actually in the air.  I
hope that explains my reasoning.

-Mike

"Ray T. Bentley" wrote:

> 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
>
> The difficult, I do right away.  The impossible takes a little longer.
> > From: Michael Jorgensen <jorge1ml@cmich.edu>
> > Reply-To: caut@ptg.org
> > Date: Tue, 22 Jan 2002 10:32:47 +0000
> > To: caut@ptg.org
> > Subject: Re: Temp fluctuation affect?
> >
> > Hi John,
> > It might help preserve the tuning.  Lowering temperature, increases
> > relative humidity.  Since wood absorbs moisture faster than it gives it
> > up,  there would be an overall higher moisture level in the wood during the
> > dry season.
> > Just a thought,
> > -Mike Jorgensen
> >
> > John Minor wrote:
> >
> >> Anyone have any hard evidence(or direct experience) with tuning
> >> instability caused by regular temperature fluctuations? Several private
> >> customers are in the habit of turning the thermostat on 60 degrees F at
> >> bedtime. (brrrrrr) Daytime temps are 68-70ish. Would this wreak havoc on
> >> tuning?
> >>
> >> John Minor
> >> University of Illinois
> >
> > -Mike
> >
> >