On Mon, Jan 24, 2011 at 5:42 PM, Jon Page <jonpage at pianocapecod.com> 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. > I left the knee board on, > > I could hear the center's pitch migrating as I was > heading into the treble. > Which is why you give it 10 minutes to acclimate *before* beginning the tuning. Change the pads first. Talk to the customer, etc. Then tune. > > Even if I had done action adjustments while the piano acclimated, > it would have still gone out once the piano was closed up. > It goes to an overall different pitch level once closed up, but the tuning "arrangement" stays the same once the temperature changes take full effect. In the case of verticals with DC systems, just make an allowance for pitch shift once the lid is closed ... so it will be at A440. Pitch shift happens even without a DC system. I was tuning today in a church with one of those programmable thermostats. The heat turned off midway, and the temperature went from 70º down to 64º by the time I finished. The tuned upper treble octaves were noticeably sharp. I know for certain as I was tuning the single octaves that I didn't leave the double octaves beating 2 bps. But by the time I was finished, things had changed. This piano has a DC system in it, but it had acclimated for over an hour with the lid up. It was totally temperature related. Last week, tuning a piano without a system, the heater vent pointing directly at the piano. All this heat is blowing on me and the piano for half the tuning. Then it shuts off. Geez, what to do? Tuning is all wacked out. I don't try to fix it because I don't know where it's gonna end up. Shift happens. :) > > 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. > > Makes sense to me. Now if you can get your customers to extricate and install the tank once a year, or pay you to do it, it should be fine to do it that way. Good luck. :) And I'd hate to think what would happen when someone waters the piano with the tank removed. Ick! > I have always said, humidify the room first and then if you need > to micro-manage the piano's RH add a DC. 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. > > The effect doesn't "dissipate." Wood moisture content doesn't change that rapidly. Tuning changes resulting from moisture content in the wood start happening in hours/days--not minutes. It's the sudden temperature change that causes that immediate pitch change. A similar effect happens when you use a heat gun to "burn"/twist a hammer shank. All that heat drastically lowers the pitch of the section that received the hot air. But once it cools, it goes back to exactly where it was. One of those laws of thermodynamics. :) -- JF -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110124/afceec55/attachment-0001.htm>
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