Tom,

No doubt Owen Daly and others in the Pacific NW will weigh in with 
useful advice: if it contradicts mine, believe them over me!

I had similar problems.  Indiana was 80% in summer and hit 20% in 
winter.  Michigan was not as humid (summer only lasts two weeks) but 
got down to 20%.  Much depends upon the RH at which the soundboard 
was installed.  I installed that in my Italian in Michigan in winter, 
so I have no problems with it.  There is not much that needs to be 
done about high RH for my Flemish double, but I do keep the RH up to 
40% in winter.

I recommend that in winter you put your instrument in a small room 
and keep the door shut.  The door, windows and walls will still leak 
moisture, but you can control that in a small room with a decent 
humidifier.  The only humidifier I would personally consider is the 
Venta.  They are not cheap, but they work and last.  Before getting 
one, I bought a lot of devices from Target and places.  They were all 
inadequate and did not survive long.  Venta also sell an electronic 
hygrometer.  I have no idea how accurate it is; I have found it to be 
quite adequate for this purpose.

If you have a small crack in the treble, as many harpsichords do, you 
can use that to show you whether the RH is getting too low, as it 
will open up!  Alternatively, get hold of a piece of spoundboard wood 
an inch or so wide and about 2-3 ft long.  The grain should be 
parallel to the short side.  You can measure the length of this piece 
of wood once a week and, after a couple of cycles, you will be able 
to tell from these measurements when the humidity is getting low.

There is a lot written on this subject in the archives.

David

At 23:51 05-05-16, Tom Mcgreevy wrote:
 >
 >Can anyone give me some guidance on what is a good level of humidity
 >to maintain for the health of my harpsichord?
 >I live in Oregon where for most of the year the humidity is 80% but
 >then for two brutal summer months it can drop to 20% or less.  So all
 >year I've been running a dehumidifier at about 50% but now it's going
 >to start getting dry as a bone around here.
 >Any advice would be very welcome.
 >Thanks,
 >Tom 

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