[pianotech] DC (was:To unplug or not to unplug)

[Ron Nossaman]

On 1/24/2011 5:42 PM, Jon Page wrote:
> This past summer I tuned a vertical with a full DC system.
>
> The AC was going and the house was rather cool.
> When I opened the piano, the interior felt warm and humid.

Yes, and if the piano had a cover, it feels even more warm and humid 
when you open it, and goes even farther out if you try to tune it before 
the strings cool down.


> I left the knee board on,

??? Do you normally not?


> I could hear the center's pitch migrating as I was
> heading into the treble.

Yes. That's why you give it, like John Formsma said, ten minutes to warm 
up before you start.


> Even if I had done action adjustments while the piano acclimated,
> it would have still gone out once the piano was closed up.

It will with any temperature difference between the inside and outside 
of the piano. Back in the day of analog watches, it was often a quarter 
to four. With everyone having digitals now, it's 3:43:31. The physical 
realities in the piano are the same aurally, but there are more decimal 
places to worry about with the ETD. If you were to warm the room up to 
the temperature inside the piano before starting, the tuning would go 
smoothly even though heating the room lowered the RH% of the room 
significantly below that of the interior of the piano.


> I'm not a fan of keeping a water tank in/under a piano
> in the summer. Why have a humidity source in an already
> humid climate. I think it's a good time to pull the tank out
> for cleaning and then replace it in the Fall.

You must have similar rich and gullible customers to the guys who charge 
for 2¢+ pitch corrections twice a year. Smoke 'em if you got 'em.


> I have always said, humidify the room first and then if you need
> to micro-manage the piano's RH add a DC.

And dehumidify the room as necessary too. I agree absolutely.


>It makes no sense to
> 'climatize a piano' and have the DC's effect dissipate when opened
> because the piano is acting as a humidifier for the room.

And as has been pointed out 3 or 79 times in the last couple of years, 
those short term tuning effects are entirely temperature related, not 
humidity.
Ron N