On Dec 17, 2009, at 2:22 PM, Jeff Tanner wrote: > Temp under the lid - in the dark - was 73.5 and the temp on the > table next to the piano was 73.0, bright lights in the room, etc. > That's half a degree. I don't think a difference in temperature that small is significant. If it gets above 2 degrees, then maybe you start to take notice, and at some point it actually affects things. In my own experience of sticking my thermo-hygrometer various places in and on D/C installed pianos over 20 years or so, I haven't seen any temperature difference more than a degree. This includes up on top of beams in bottom cover installations, under a closed lid of a grand, inside a bottom panel of a upright, etc. That's not to say it couldn't happen, but it hasn't happened on any of the pianos I service. I suspect that bigger temperature effects (D/C produced effects, that is) would happen in higher humidity climates, since the drying rods would be activated more (though I haven't seen it here during our high humidity season). And that heat could build up when a piano is covered, especially an upright. I don't have any uprights with covers and with D/Cs. I'd be curious to know what anyone has actually measured in terms of temperature differences inside and outside a covered piano. I think it would be especially interesting to know about grands with full length covers, since they are likely to be concert instruments. If there is enough temperature build up to cause pitch drift for 15-20 minutes after uncovering, that would certainly kill the deal for me. I can't spend that long twiddling my thumbs. A lot of times there is just a half hour window of access to the hall for a touch up, and losing half of it waiting for the instrument to settle down is out of the question. And I can't see having the performer uncover an instrument and experience pitch and tuning drift for that long, and it not being a pretty significant problem. Even 5 to 10 minutes would be an issue, though maybe more livable. I think a few on the list have installed such covers on pianos with full D/C systems, so maybe they have some experiences to share that would shed some light. Seems like an important thing for us all to know. Regards, Fred Sturm University of New Mexico fssturm at unm.edu
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