Humidity Change and Unisons

[John Lillico, RPT]

At 08:36 PM 08/17/2000 Don Rose stated

>Hi John,
>
>I agree that a broken string will cause the plate to move. But the same
>effect would happen without a soundboard/wooden support structure. How does
>humidity affect the plate? (Other than rust in extreme cases). 
>
Don,

I was tempted to say, "heavy metal" but........

Throw away the soundboard and bridge and just have your strings and plate. If the plate doesn't swell with humidity, although I think it might, it will at least be tilted somewhat through expansion of that upon which it rests. The plate edge beyond the bridge keeps getting longer, not by note but by string. This is on both grands and uprights and that's why your right string is found to be at a greater tension than the left.

This may not be as extreme where you have those "adjustable" duplux doohickeys on some grands though.

John Lillico, RPT
Oakville, Ontario