I believe the blanket could be at the source of the problem in combination with lack of air flow, humidity levels, use of humidifiers for dry air in the winter months.
I do not think a geo-thermal system has anything to do with this. Geo-thermal is an efficient system used to heat and airconditioning by storing heat pulled from the air and storing it in the ground. there are two types- a closed loop and open loop but at no point is air with minerals in it circulated. There can be dust in the ductworks of the home that frequently gets there during drywall construction . If that is the case it would be all over furniture, on top of the piano, on floors etc. I have a closed loop geo-thermal system and I do not have anything on top or under the lid of my G2 Yamaha
The white film is a white dust that may be a form of light mold. The lid is probably sweating from the blanket and heat used for winter heating. I see certain types of mold here when there is poor drainage of ac systems, equipment is broken or not properly serviced . Deep cycling- shutting off or turning down the temp at the thermostat and then running at turbo speed can cause molds.
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James Kelly
Owner- Fur Elise Piano Service
Pawleys Island SC
843-325-4357
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Original Message:
Sent: 04-11-2021 09:51
From: Martin Snow
Subject: Fine "dust" coating on underside of Steinway lid
John, this is interesting, one of my very regular concert venues for maintaining 2 in house Steinway model A pianos was a museum that had a very elaborate but effective climate control system both for the galleries and the lower level where the pianos were housed and also workshops for ongoing conservation and storage of museum owned art and Shaker collections not in the current rotational display in the galleries. A large freight elevator delivered the piano of choice one day prior to concert and I would tune morning of recital.
There often was identical white micro 'dust' primarily on underside of main lid that the curator would remind me to wipe away, I never thought to ask him if the museum HVAC system was a "geo thermal heat pump " of which you speak . I have never encountered this in other pianos. Martin.
www.snowpianos.com
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Martin Snow
South Burlington VT
617-543-1030
Original Message:
Sent: 04-10-2021 23:00
From: John Minor
Subject: Fine "dust" coating on underside of Steinway lid
Customer has a 1920 Steinway M that has a very fine coating of "dust" on the underside of the lid and fallboard on the decal side. I wondered if it might be mold. Customer leaves piano closed up and covered with a blanket. The dust wipes off easily, but I'm wondering if this has something to do with their HVAC being geo-thermal heat-pump that runs more constant than conventional HVAC system. Under a bright flashlight the dust has a slight sparkle to it. Any guesses on what it might be? I've seen similar dust from ultrasonic humidifiers that are known to leave a "white mist" on some surfaces.
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John Minor
The Piano Shop Inc
Champaign IL
thepianoshopcu@gmail.com
www.thepianoshopcu.com
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