Where did the RH Go

[DIANE HOFSTETTER]

Sarah,

For fourteen years now my partner and I have been measuring and graphing the 
tuning on every piano immediately before we tune it.   We also record the 
relative humidity and temperature most of the time, whether it has a 
Damppchaser installation or not, and if it is functioning correctly.

Then when we next tune the piano and record all the data again, we have a 
way of understanding how to service the piano to make the tuning as stable 
as possible.

Over the years I have had fun with a variety of experiments.  One day I 
arrived to tune a piano in a room that is routinely kept unheated with no 
climate control in the piano.  The maintenance people had just turned on the 
heat before I arrived and a stream of warm area was shooting out of the 
register about ten feet away.

I was dismayed; the heat should have been turned on hours before.  I knew 
the tuning could not be reliable.  I went ahead and graphed the tuning.  As 
soon as I finished that graph, I remeasured the tuning and graphed it again. 
  Then I remeasured and regraphed, and then once again.  I ended up with a 
graph showing four distinctly separate lines of the tuning as it changed 
with the relative humidity and temperature for each line carefully recorded.

There is no question in my mind that changes in relative humidity affect the 
tuning dramatically and that a Damppchaser system does an excellent job of 
helping control that.  I have numerous graphs to show it does.

Diane





Diane Hofstetter





>From: "Sarah Fox" <sarah@gendernet.org>
>Reply-To: Pianotech <pianotech@ptg.org>
>To: "Pianotech" <pianotech@ptg.org>
>Subject: Re: Where did the RH Go
>Date: Mon, 12 Jan 2004 21:48:30 -0500
>
>Hi Don,
>
> > I did not say your system didn't work. What I said was a DC system would
> > work even better.
>
>Perhaps.  Perhaps not.  I don't mean to be argumentative on this point.  
>I'm
>really asking a question here:  Have you (or has anyone else) done
>measurements with a good, accurate hygrometer on a complete DC grand
>installation, during dry ambient conditions, showing that humidity is 
>indeed
>evenly distributed all over the soundboard, both under and on top, and in
>the action cavity?  Also, have the same measurements been done inside the
>piano with a closed lid and inside the action cavity during predominantly
>dehumidifying periods?  In other words, are DC's claims fully 
>substantiated,
>as determined empirically with a hygrometer?  I've heard lots of claims
>regarding stability of pitch.  That's all well and good, of course.
>However, how well does the DC system regulate humidity (in contrast to
>pitch)?
>
> > I do recommend room type humdifiers as well--but only to "assist" a DC
> > unit. If it is a choice of one or the other the DC provides much better
> > year round control than is generally possible with a room type. There 
>are
> > exceptions, but they are very rare.
>
>This sounds like a reasonable approach.
>
> > Do you have measurements for the summer time? Where I am I have 
>documented
> > as low as 4% and as high as 84%.
>
>Without humidification, humidity levels inside my house vary from 27% in 
>the
>winter to 67% in the late fall.  I have forced heat and refrigerated A/C,
>BTW.  I suspect humidity levels are far different in other parts of the
>state.  I'm in Central Ohio.  In the lake areas, humidity is undoubtedly
>much higher during moderate weather.  Also, I have no idea what humidity
>levels occur in other people's homes here in Columbus.  (I don't service
>their pianos. <grin>)
>
> > I would love to have a controller for a DC type system that had much
> > narrower limits. I know, for example, that rare bird hatcheries have 
>units
> > that are calibrated to 1/10 of one percent humidity that power an
> > "electronic" fan (read no blades--some sort of vibrating plate) combined
> > with an ultrasonic humidifer. I'd love to get my pinkies on one!
>
>Well, I can't boast 0.1% limits with my system (WOW!!), but I do quite a 
>bit
>better than the specs DC boasts.  I did a 100% non-DC-brand installation on
>my concert grand, using a GE humidistat that cycles the system adjustably
>between 40 - 44% (or occasionally as widely as 39 - 45%) when the ambient 
>RH
>is in the upper 40's.  The installation is fairly recent, so I haven't yet
>been able to observe its behavior at higher humidity levels.  I'll give you
>an update in the spring if you're interested.
>
>Peace,
>Sarah
>
>
>
>
>_______________________________________________
>pianotech list info: https://www.moypiano.com/resources/#archives

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