Humidity (Moisture mystery)

[Michelle Smith]

Hi Jere and others-

It's interesting that you posted this today.  I tuned a piano for a customer
6 weeks ago and encouraged them to resume use of their Dampp Chaser system
that had been left off for a couple of years.  (We replaced the pads and
filled it with water and the bottled solution.)

They have since kept it hydrated and called to say that the pitch was off
and could I come take a look.  As I assumed would happen, some of the notes
were pretty out of whack but to my real surprise, the whole piano (except
for the high treble) was 14 cents FLAT!  I was quite surprised because I
thought the addition of all that water would cause it to go sharp.

Anyone have any ideas of what happened here?  (I have my own theory but want
to hear from some people with more experience.)

Thanks!

Michelle Smith
Bastrop, Texas


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of jere fryett
Sent: Tuesday, October 10, 2006 7:59 PM
To: pianotech at ptg.org
Subject: Humidity

List,

Sometime in the past someone wrote about how humidity changes affect pitch 
changes.  In the article they said that for every % in humidity change the 
pitch changes by a certain amount also.  I have been searching the archives 
and I can't find those figures.  Does anyone know how much the pitch will 
change with every % of humidity change?

I need this to make a point at our local college.

Jere

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