[CAUT] FW: Temperature/Humidity range

[John Ross]

At the University, I do the pianos for, they had a humidity controlled 
space for a new Yamaha CF.
This was my first year.
The person, that sold them the CF, said just controlling the humidity, 
was all they needed to do.
They had a Steinway D in there, and when I had it taken out to tune in 
the summer, the moisture, condensed on the plate, the hammers went up 
and wouldn't come down. The piano was saturated.
I determined, that the dehumidifier, was cooling the place down, and 
when it came out to the stage, the coolness caused water to condense on 
the piano.
I told them, that in this situation, they needed heat to be controlled 
as well.
They had obviously, assumed that the room's temperature would be the 
same as the schools, but the dehumidifier, acted like a refrigerated 
space.

I am not disagreeing with Ron, just indicating that exceptions can 
happen.

John M. Ross
Windsor, Nova Scotia, Canada
jrpiano@win.eastlink.ca
----- Original Message ----- 
From: "Ron Nossaman" <rnossaman@cox.net>
To: "College and University Technicians" <caut@ptg.org>
Sent: Saturday, January 14, 2006 5:56 PM
Subject: Re: [CAUT] FW: Temperature/Humidity range


>
>> I'd say that temp will be fine if it's comfortable for the people in 
>> the
>> building. IOW, a reasonable small range, which will typically be 
>> between 68
>> and 75 F. They'll have to maintain that to keep the people happy. 
>> (Yes, Ron
>> is correct that you might have your pianos happiest at a constant 50
>> degrees, but that ain't gonna happen).
>
> Hi Fred,
> Well, no, that's not what I meant. My point is that the temperature 
> can fluctuate quite a bit (even with the heating thermostat set at 50° 
> in the old country church, it often gets considerably warmer than that 
> as the weather fluctuates), and the pianos keep up fairly well. It's 
> the humidity extremes resulting from trying to keep a constant 
> temperature, that are the problem causing the major seasonal pitch 
> changes. The MC of the wood in the piano is what we're trying to 
> control indirectly. For instance, a temperature of 70°F, with a 42%RH 
> results in an 8%MC in an arbitrary piece of wood (piano) stored in 
> those conditions. Keeping the RH% at  42 when the temperature drops to 
> 50°F results in only a 8.2%MC in the piano, where maintaining 70°F 
> temperature and driving the humidity down to fairly mild 35%RH results 
> in a 6.2%MC and a pitch raise. Each degree F change at a given RH% 
> results in a bit over 0.01%MC change. Each 1% change of RH at a stable 
> temperature results in approximately 0.15%MC change. So, given the 
> choice, I'd not spend too much time worrying about temperature 
> control, and try to get control of the relative humidity.
>
> Ron N
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