Whole room humidity control better than Dampp Chaser. ( Right?)

[Farrell]

I disagree almost completely. If the piano lid is left open, yes the DC unit would likely have little ability to deter rust forming on strings. But if the lid is kept closed, and of course, better yet, if a string cover is used, and, of course, better still yet, if a nice thick quilted full piano cover is used (that means placed on the piano!), the DC unit will indeed very effectively deter the formation of rust on strings.

If one were trying to add humidity to the environment on top of the soundboard, indeed, a DC humidifier placed on the bottom of the soundboard would have little effect. That is because the humidifier physically adds water molecules to the air, and if there is a barrier (soundboard panel) to the migration of those molecules, then the water vapor will stay in the environment of their origin (below the soundboard). 

However, the holes, or lack thereof, in the soundboard have little to do with the transmission of heat. The dehumidifier portion of the DC system adds heat (raises the energy level of the air) to the environment below the soundboard panel. Heat energy can and does transmit through the panel and heats the air above the soundboard. The air below the soundboard warms, the soundboard warms and then the air above the soundboard warms. The warm air from below the soundboard does not have to mix with the air above the soundboard for the temperature above the soundboard to warm. 

In fact, if the piano could be perfectly insulated from the room environement, the temperature above the soundboard would be equal to the temperature below the soundboard after a period of system equalization. Of course that won't happen, because a piano will not be perfectly insulated from the room environment, but a good string cover or especially a good blanket should get you most of the way there.

As long as that heat above the soundboard can be retained (close lid, string blanket, whole piano cover), the environment of the strings will be at a higher temperature and thus a lower relative humidity than it would without the DC system. And thus the formation of rust will be deterred.

Terry Farrell
  ----- Original Message ----- 

  SNIP My post, however, was dealing with the prevention of oxidation and/or rust not the promotion of it. A DC unit in a grand won't do much to prevent it. One could argue that the string cover will retain some of the DC unit's effects but it seems to me that little is afforded here since the only pass through from the underside of the soundboard to the top side are through the nose bolt holes. I doubt that the amount of air passing through these holes in the board are enough to effect much of a change topside.

   

  Greg Newell
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