Pianotech

It was posted on this list recently that Dampp-Chaser humidistats responded to temperature change. I always thought that they responded to humidity and, after a conversation with Dampp-Chaser, I find that I am correct. The nylon band in the humidistat responds to humidity change. It is true that raising the temperature of a given volume of air will lower the relative humidity but the humidistat responds directly to humidity change.
It was also posted that the boundary layer was “molecules thick.” That suggests to me something that is easily countable, like 10 molecules or 1000 molecules. Molecules are really, really small and there is a lot of space between air molecules. If the boundary layer were only 1000 molecules thick, I don’t see how the system could work at all. I don’t think anyone is able to measure exactly how thick that boundary layer is but 1/4” sounds like something much more reasonable.
It was also posted earlier that the boundary layer couldn’t reach the end of the soundboard in a 7’ grand. I don’t buy that at all.

Bob Anderson, RPT
Tucson, AZ

There may have been some miscommunication on that thread.  I don't think anyone was talking about how the Damp-chaser humidistat registers its readings. It is after all a humnidistat, so it makes sense that it cycles on and off relative to rh changes.

My understanding of the discussion was questioning whether we ascribe changes to tuning as a result of humidity, when, perhaps, since RH and temp always change together, changes in temp were actually more responsible for the pitch changes, than the humidity.  Maybe its both temp and humidity,  and maybe its predominantly one or the other. we don't have any decent data, because temp and rh, in ambient conditions change together, always. One would have to design an environmental chamber that could change temp while maintian constant RH, and visa versa. Its probably doable with some fancy equipment....but I don't see that test happening anytime soon.

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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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Original Message:
Sent: 07-19-2021 11:29
From: Robert Anderson
Subject: Dampp-Chaser systems

It was posted on this list recently that Dampp-Chaser humidistats responded to temperature change. I always thought that they responded to humidity and, after a conversation with Dampp-Chaser, I find that I am correct. The nylon band in the humidistat responds to humidity change. It is true that raising the temperature of a given volume of air will lower the relative humidity but the humidistat responds directly to humidity change.
It was also posted that the boundary layer was "molecules thick." That suggests to me something that is easily countable, like 10 molecules or 1000 molecules. Molecules are really, really small and there is a lot of space between air molecules. If the boundary layer were only 1000 molecules thick, I don't see how the system could work at all. I don't think anyone is able to measure exactly how thick that boundary layer is but 1/4" sounds like something much more reasonable.
It was also posted earlier that the boundary layer couldn't reach the end of the soundboard in a 7' grand. I don't buy that at all.

Bob Anderson, RPT
Tucson, AZ

Re the barrier layer, the "molecules thick" theory comes from laboratory experimentation undertaken in the height of the oil crisis in the 70's. They were trying to assess how the insulating properties of insulated glass worked. The conclusion was, that the barrier layer was a molecular layer. I'd have to dredge the study up somewhere. Nobody has tested it on a piano, of course, and, again, I don't see that happening anytime soon either. This leaves us with plenty of ammunition to continue a rather inconclusive discussion for the rest of eternity.

------------------------------
Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
------------------------------

Original Message:
Sent: 07-19-2021 14:59
From: Jim Ialeggio
Subject: Dampp-Chaser systems

There may have been some miscommunication on that thread.  I don't think anyone was talking about how the Damp-chaser humidistat registers its readings. It is after all a humnidistat, so it makes sense that it cycles on and off relative to rh changes.

My understanding of the discussion was questioning whether we ascribe changes to tuning as a result of humidity, when, perhaps, since RH and temp always change together, changes in temp were actually more responsible for the pitch changes, than the humidity.  Maybe its both temp and humidity,  and maybe its predominantly one or the other. we don't have any decent data, because temp and rh, in ambient conditions change together, always. One would have to design an environmental chamber that could change temp while maintian constant RH, and visa versa. Its probably doable with some fancy equipment....but I don't see that test happening anytime soon.

------------------------------
Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026

Original Message:
Sent: 07-19-2021 11:29
From: Robert Anderson
Subject: Dampp-Chaser systems

It was posted on this list recently that Dampp-Chaser humidistats responded to temperature change. I always thought that they responded to humidity and, after a conversation with Dampp-Chaser, I find that I am correct. The nylon band in the humidistat responds to humidity change. It is true that raising the temperature of a given volume of air will lower the relative humidity but the humidistat responds directly to humidity change.
It was also posted that the boundary layer was "molecules thick." That suggests to me something that is easily countable, like 10 molecules or 1000 molecules. Molecules are really, really small and there is a lot of space between air molecules. If the boundary layer were only 1000 molecules thick, I don't see how the system could work at all. I don't think anyone is able to measure exactly how thick that boundary layer is but 1/4" sounds like something much more reasonable.
It was also posted earlier that the boundary layer couldn't reach the end of the soundboard in a 7' grand. I don't buy that at all.

Bob Anderson, RPT
Tucson, AZ

Robert - I don't recall the thread you refer to. What is the "boundary layer"? A boundary layer reaching the end of a soundboard??? I don't understand at all.

------------------------------
Terry Farrell
Farrell Piano Service, Inc.
Brandon, Florida
terry@farrellpiano.com
813-684-3505
------------------------------

Original Message:
Sent: 07-19-2021 11:29
From: Robert Anderson
Subject: Dampp-Chaser systems

It was posted on this list recently that Dampp-Chaser humidistats responded to temperature change. I always thought that they responded to humidity and, after a conversation with Dampp-Chaser, I find that I am correct. The nylon band in the humidistat responds to humidity change. It is true that raising the temperature of a given volume of air will lower the relative humidity but the humidistat responds directly to humidity change.
It was also posted that the boundary layer was "molecules thick." That suggests to me something that is easily countable, like 10 molecules or 1000 molecules. Molecules are really, really small and there is a lot of space between air molecules. If the boundary layer were only 1000 molecules thick, I don't see how the system could work at all. I don't think anyone is able to measure exactly how thick that boundary layer is but 1/4" sounds like something much more reasonable.
It was also posted earlier that the boundary layer couldn't reach the end of the soundboard in a 7' grand. I don't buy that at all.

Bob Anderson, RPT
Tucson, AZ

I was referring Jim Ialeggio’s post of 6/26/21 on the thread “Dampp Chaser, extreme humidity changes?”, Terry. He posted a clarification yesterday afternoon. Perhaps you have seen it by now. I apologize for taking so long to reply but I seem to do everything pretty slowly these days.
Anyway, Jim wrote “The system moderates the RH using temp of soundboard. The conditioning happens, relative to temp, on a layer of air adjacent to the board called the ‘barrier layer’ (a better term than my ‘boundary layer’). This conditioning layer is only molecules thick.”

I don’t remember whose post it was (shortly before the above) but he wrote that Dampp-Chasers had to be watered every day and that the ‘barrier layer’ (although he didn’t use that exact term) couldn’t reach the ends of the soundboard on a 7’ grand. I didn’t take this seriously because it suggested to me that he had only heard about Dampp-Chasers but didn’t have any experience using them. I don’t claim to have the last word about it but I came to my own conclusion very early in my career that humidity control was important and I installed a system in my own grand to see how it worked. After concluding that it did work, I started installing Dampp-Chasers in other pianos. That has been over 40 years ago. I know that other technicians have had different experiences, but that has been mine.

BTW, I thought that Charles Rempel of Dampp-Chaser used to have very useful comments on humidity control. I discovered that he is no longer working in the piano industry.

Bob Anderson, RPT
Tucson, AZ


Original Message:
Sent: 7/20/2021 5:22:00 AM
From: Terrence Farrell
Subject: RE: Dampp-Chaser systems

Robert - I don't recall the thread you refer to. What is the "boundary layer"? A boundary layer reaching the end of a soundboard??? I don't understand at all.

------------------------------
Terry Farrell
Farrell Piano Service, Inc.
Brandon, Florida
terry@farrellpiano.com
813-684-3505
------------------------------

Original Message:
Sent: 07-19-2021 11:29
From: Robert Anderson
Subject: Dampp-Chaser systems

It was posted on this list recently that Dampp-Chaser humidistats responded to temperature change. I always thought that they responded to humidity and, after a conversation with Dampp-Chaser, I find that I am correct. The nylon band in the humidistat responds to humidity change. It is true that raising the temperature of a given volume of air will lower the relative humidity but the humidistat responds directly to humidity change.
It was also posted that the boundary layer was "molecules thick." That suggests to me something that is easily countable, like 10 molecules or 1000 molecules. Molecules are really, really small and there is a lot of space between air molecules. If the boundary layer were only 1000 molecules thick, I don't see how the system could work at all. I don't think anyone is able to measure exactly how thick that boundary layer is but 1/4" sounds like something much more reasonable.
It was also posted earlier that the boundary layer couldn't reach the end of the soundboard in a 7' grand. I don't buy that at all.

Bob Anderson, RPT
Tucson, AZ