Pianos are not the only objects to suffer from mold.  Our saddles
got it.

The circulation blower motor for our new heating and air-conditioning
system died, due to a manufacturing defect.  The local air-conditioning
company could not get the correct replacement motor immediately (it was
a variable-speed motor that ran on DC through a smart controller) so they
installed a single-speed AC motor, uncontrolled, and always operating.

Normally the air conditioner removes water from the air as it condenses
onto the chilled coils, and then the water drips down into a pan from
which a tube carries it outside.  Because the circulation fan never
stopped, the water never dripped down.  Every time the cooling cycle
ended, the blower picked it up and put it back into our house!

The result?  Mold all over anything leather.

High humidity is sufficient to grow mold on leather, regardless of
what treatments might have been used.  Verbum sapienti sat est.

Peter Neilson
Sanford NC