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Fine "dust" coating on underside of Steinway lid

  • 1.  Fine "dust" coating on underside of Steinway lid

    Registered Piano Technician
    Posted 04-10-2021 23:01
    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.

    John Minor
    The Piano Shop Inc
    Champaign IL

  • 2.  RE: Fine "dust" coating on underside of Steinway lid

    Registered Piano Technician
    Posted 04-11-2021 01:12

    If it's  white dust, it's  a non-harmful type of mold. Just wipe off, and provide more air flow for the piano.


    Sent from my Verizon, Samsung Galaxy Tablet

  • 3.  RE: Fine "dust" coating on underside of Steinway lid

    Posted 04-11-2021 09:51
    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.

    Martin Snow
    South Burlington VT

  • 4.  RE: Fine "dust" coating on underside of Steinway lid

    Registered Piano Technician
    Posted 04-11-2021 10:59
    Hammer felt? Especially if you have ever filed the hammers.
    Fred Sturm
    "Tradition is not the worship of ashes, but the preservation of fire." -Gustav Mahler

  • 5.  RE: Fine "dust" coating on underside of Steinway lid

    Posted 04-15-2021 16:24
    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.

    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC