Sarah, I'd say that DC systems are doing a good job, if enclosed, always better to have some water ready near the instrument than none, . The biggest point that is always untold about the R.H regulation is that the 42%,45% or whatever number we consider ideal for an instrument is not meaning the same in a cold atmosphere or a warm one. Assuming that people tend to warm more their places in winter than necessary, and that then the inside temperature is higher than during the nice season, as I noticed often : I'd say that it is fairly acceptable to have 40% moisture in air during winter in warm rooms and that is , from a wood moisture point of view, about the same than having 50 % moisture during summer, so our instruments are accepting a slightly wider range of H.R. than we think, and saying that we want to keep a permanent 45% HR without mention of the room temperature , is not telling the whole story. For us human beings, a somewhat cold (18° 20°)place is comfortable with 50% to 60% H.R, a more tempered one (21-23°)from 40% to 50%, while a warm one 524°-26°) is cool with 40-45% R.H. The same idea apply to pianos to a lesser extent, a few degrees centigrade change in air change drastically the H.R. , while the real amount of water (in weight) stay the same. what changes is the tension state of the vapor making it more or less efficient to go thru materials (but I don't know how to deal with this concept) I don't know how to tell you that in Farenheight degrees so it is up to you to look in wood moisture tables to have an idea about what it mean. It have been usual in our climates to admit 40% in winter up to 50% in summer as very acceptable conditions for pianos. But indeed that does not mean not warning against extreme dryness as it occurs in winter or the high rise of humidity, that all together give the cracks and other problems. With all the best. Isaac OLEG Entretien et réparation de pianos. PianoTech 17 rue de Choisy 94400 VITRY sur SEINE FRANCE tel : 033 01 47 18 06 98 fax : 033 01 47 18 06 90 cell: 06 60 42 58 77 > -----Message d'origine----- > De : pianotech-bounces@ptg.org > [mailto:pianotech-bounces@ptg.org]De la > part de Sarah Fox > Envoyé : vendredi 11 avril 2003 16:50 > À : Pianotech > Objet : Climate Control; DC thoughts and concerns > > > Hi all, > > I've been reading the soundboard torture and killer octave > posts with > considerable interest. One of the results of these posts > has been a lot of > comments to the effect of, "It surely goes to show how > important it is to... > (insert some climate control maxim here)." > > This has all started me to thinking about the climate > control situation > around my own piano. You see, I have a very difficult > house. Unless I were > to put my piano up against the fireplace or in the kitchen > against the sink, > I have no usable interior walls. Perhaps a bedroom? I > think the piano is > bigger than any of the bedrooms, aside from the upstairs > master. Bathrooms > are not a likely option. > > Kidding aside, my exterior walls are my only option. They > are each around > 75% glass (double-paned) and are where the heat registers > are located. I > realize exterior walls are not as significant a problem for > a grand piano as > an upright, but should I still be concerned? Of course I took the > precaution of blocking the heat registers in the room and > allowing the room > simply to get the cross-flow from the adjacent rooms -- still quite > comfortable. I spaced the piano about 2 feet from the > window, and I have a > ceiling fan in the room to keep the air stirred/mixed. > During the dead of > winter (Ohio), I have insulated drapes for protection. Is > anything about > this arrangement problematic??? > > I am also about to install climate control devices. I will > be putting a DC > dehumidifier system in the piano for the moderate months. > (The piano will > soon be making a move to a warm, humid climate, so I will > definitely need > this.) I am left wondering about the humidification end of > DC's system, > though. I'm not sure I entirely trust the thing. I'm also > left wondering > whether a tiny column of water vapor from the humidifier > will really spread > over an entire sounding board and not just condense in the > middle and/or > waft away. The system also presupposes that the moisture > doesn't just > evaporate back out of the board on the top-side, resulting > in a MC still > somewhat less of where it should be. Finally, it appears > to me that the > heater bars and humidifier would be alternately fighting > each other in the > complete system. Is it really smart to heat the board during dry > conditions, even if the (tiny) humidifier is also adding > moisture? Would > this not speed moisture loss on the top side? It doesn't compute. > > It seems to me a much better approach would be to humidify > the area. My > house dropped to a low of 28% RH this winter -- not so low > as to throw me > into a panic, but low enough that my piano complained > somewhat. Anyway, the > DC system cycles over about a 12% RH range, as I recall. > It would only take > an additional 8% RH to put my house at the low end of this > range. Fifteen > percent would put my house in the middle of the range. > Would this small > amount of added humidity really pose a problem for my house? > > I figure I could humidify the house to a minimum of 40% RH, using a > whole-house humidifier/humidistat system. Then the DC > heater bars could > kick in during higher humidity conditions to drop the > microclimate RH to its > 36-50% RH range during the moderate months. There would of > course be no > heater bar activity during the winter. > > If I opt for whole room (vs. whole house) humidification, > how far away from > the piano should the humidifier be? (I would be using an > ultrasonic unit > with distilled water.) Remember that I have a ceiling fan > to keep the air > slowly stirred. > > Misc. concerns about the DC: > > The same would be true of the dehumidification process as > the humidification > process: Heat would escape the soundingboard from the > topside, and so the > effective temperature of the board would be roughly the > numerical average of > the air temperature above and below the board. Thus, the > board would not > really be kept at its target MC. The error would increase in direct > proportion to the overall magnitude of correction. Let's > say the ambient RH > is 100%, and the DC system raises the underside temperature > to achieve an > ambient RH of 42%. The net effect, I believe, (making > liberal assumptions > here) would be an effective overall RH of 71% in the microclimate > surrounding the board. If there were also a heater bar > under the closed > lid, conditions would of course be better. It seems to me > that the DC is > only really effective at fine-tuning the RH. Perhaps the > prudent piano > owner would also keep a room/household > dehumidifier/humidistat running to > keep the RH down to a max of, say, 60%? > > In the grand installation, there's no heater bar behind the > action, under > the pin block. Why? Would it not make sense to have a > second humidistat > and heater bar -- perhaps attached to the backside of the action? > (Incidentally, the need for keeping the MC of my pin block > and action parts > up during the winter makes me believe all the more in > whole-room/house > humidification.) > > I don't know if I'm being too compulsive here, but the > little soundboard > torture experiment.... Wow! > > Any advice and/or perspectives would be greatly appreciated. > > Peace, > Sarah Fox, > Chilly Columbus, OH > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives >
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