<html> <body> Terry, Wool does absorb and release.  I'm thinking of extremes.  Common example: air-conditioned house, door opened for guest, warm wet air blows over cold dry plate and strings and you quickly have visible condensation.  Not with a cover.  The humidity doesn't hit all at once. Barrier or buffer, it still works well. Andrew At 09:19 AM 2/18/2008, you wrote: <blockquote type=cite class=cite cite="">Andrew - I've heard this before. I'm not going to argue against it, but I have to admit it makes no sense to me. Perhaps I just don't understand. Logic tells me that if the wool cover "buffers" humidity, that means it absorbs humidity. Humidity is water vapor, i.e. water molecules. So where does the water go then? At some point, the blanket is going to start dripping when it reaches saturation.   If one were to ring the wool cover out now and then and discharge the water that way, I could understand, but otherwise it seems impossible to me. What is the physical/chemical mechanism at work here?   Are you aware of any authoritative source of information regarding this?   Thanks.   Terry Farrell <dl> <dd>----- Original Message ----- <dd>A wool-felt string-cover alone will protect the strings against rust.  That has been well established by grand pianos in (ocean front) beach-houses with string-covers that have brand-new looking interiors after decades as compared to their unprotected neighbors.  Wool has the natural capacity to buffer humidity and any sort of cover probably prevents condensation.  This is the first accessory I recommend. <dd>Add a DC system and undercover and you will then reduce the sound-board oscillation to negligible resulting in tunings that last until your next service.  You get to do a concert level tuning each time you return to the instrument.  <dd>I have two Sauters on the floor here.  They are fine pianos which are much more stabile than average.  One has a DC with undercover and the other has DC with undercover and string-cover.  The one without the string-cover is noticeably (to me) affected by the weather.  The other one hasn't been tuned in a coon's age and still has a solid tuning on it. <dd>YMMV <dd>Andrew Anderson </dl></blockquote></body> </html>