Humidity Factor, workload

[Don]

Hi Fred,

I have data that suggests that "if" a piano is allowed to stabilize that a
5% change in R.H. causes a pitch swing of 4 cents at A4. So I think your
revision needs to have a much narrower window for "excellent" humidity
control.

At 12:09 PM 5/8/02 -0600, you wrote:
>I'm going to throw a revised humidity factor at you, based on feedback
>received both on and off list. (And don't worry, I'll compile all these
>altered numbers in one document, probably by the end of May so we can
>all chew on them for a while before convention).
>For comparison:
>> 2002 version
>> 1.3 - Excellent: 15% maximum variance in relative humidity (or has
>> humidity control unit installed and well-maintained)
>> 1.0 - Good: 30% maximum variance in relative humidity.
>> 0.7 - Fair: 50% maximum variance in relative humidity
>> 0.4 - Poor: Greater than 50% maximum variance in relative humidity
>
>revised version
>1.2 - Excellent: 10% maximum variance in relative humidity (or has
>complete humidity control unit installed and well-maintained, with back
>covers on uprights, string and bottom covers on grands)
>1.0 - Good: 25% maximum variance in relative humidity (or has complete
>humidity control unit installed and well-maintained)
>0.8 - Fair: 40% maximum variance in relative humidity
>0.6 - Poor: 60% maximum variance in relative humidity
>0.4 - Very Poor: variance in excess of 60%
>
>Notes with respect to piano installed humidity control systems:
>1) It is likely that a complete system without back/bottom/string covers
>can bring a piano into the Excellent category if the variance in the
>building is no more than 30%. Some discretion should be used in
>assigning categories.
>2) "Half systems" (a humidistat with a dehumidifying unit) can help in
>situations where ambiant humidity rises above 50% on a regular seasonal
>basis. In general, such a system might improve tuning stability by one
>step. Complete systems are strongly recommended wherever possible under
>most conditions where humidity varies more than 15%.
>3) There is a certain amount of maintenance time involved for complete
>systems. Most of this maintenance is unskilled, and can be accomplished
>by, say, a work study student, thereby freeing up technician time.
>4) Systems must have the appropriate wattage and position of components,
>as recommended by the manufacturer, to produce the predicted level of
>effectiveness.
>
>General note with respect to humidity control: 
>	Variance in humidity is by far the largest factor in maintaining tuning
>stability, and it has structural effects on the long term integrity of
>every piano (particularly soundboards and pinblocks). The effect of
>humidity variance is amplified many-fold in modern institutional
>environments, due to code requirements for HVAC systems. Modern HVAC
>systems exchange the entire volume of air in the building many times a
>day. As a result, air is in constant motion (leading to more rapid
>movement of ambiant humidity to and from wood), and changes in outside
>humidity are reflected almost instantly within buildings.
>	Hence, the importance of humidity control to the quality of piano
>service cannot be overemphasized. In all likelihood, the multipliers for
>"fair" through "very poor" are very conservative, in terms of showing
>the effect of large scale humidity change on overall tuning quality and
>general long term need for rebuilding and replacement of instuments.
>
>As always, comments and suggestions welcomed and solicited.
>Regards,
>Fred Sturm
>University of New Mexico
>
>
>

Regards,
Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.

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