Simple in principle. but not in practice.
Wood expands and contracts more across the grain than along the grain, so round holes become oval across grain when the wood moisture content increases, and oval along the grain when the wood dries.
But the process can be irregular, because the surface wood may respond faster than the full piece of wood. An open hole may first become smaller with increased humidity, then larger as the rest of the wood expands.
And then, if wood has been compressed, as in easing keys, the compressed wood may respond to humidity by swell back to its original shape.
It's a wonder anything made of wood works. (It helps if you use the right wood.)
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Ed Sutton
ed440@me.com(980) 254-7413
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Original Message:
Sent: 11-05-2017 05:18
From: Rick Butler
Subject: Is verdigris cause of sluggish Teflon Steinways?
To add to Karl's comment, a wood engineer from Kimball, Jon Light, explained the same thing; add humidity and the hole enlarges. If I remember correctly, Jon wrote an article in the Journal sometime in the mid 80's on this subject.
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Rick Butler
Bowie MD
240 396 7480
RickRickRickRickRick
Original Message:
Sent: 11-04-2017 20:23
From: Karl Roeder
Subject: Is verdigris cause of sluggish Teflon Steinways?
Mr. Blees,
I had a hard time with this too then a wood technologist (Warren Albrecht) at Steinway cleared it up for me in one sentence. " When you add humidity to the wood and the wood swells the entire part including the hole gets bigger."
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Karl Roeder
Pompano Beach FL
Original Message:
Sent: 11-03-2017 18:15
From: Willem Blees
Subject: Is verdigris cause of sluggish Teflon Steinways?
Jon
As I was writing my response I got to thinking about this effect of moisture and the hole. It's hard for me to wrap my head around the concept that when wood expands, a hole in the wood does too. I've heard about it, but it's still hard to visualize it. Mind you, I'm not arguing with you, because you have proof. It's just doesn't make sense, to me.
But the bottom line, regarding the original question, remains. Humidity changes have a big effect on Teflon bushings.
Sent from my iPhone
Original Message------
Wim, the opposite happens. When the wood takes on moisture, the wood expands and so does the hole. That's why they click in wet weather. I saw a demo where a s/f was placed in a glass of water and the bushing became loose in the yoke.
Heat's effect on the bushing is probably a cause for expanding plastic or cold causing shrinkage.
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Regards,
Jon Page
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