When to do it

[Tony Caught]

Hi Jim,

Hammer heads are made of lamb's wool felt (generally Australian lamb's wool)
and yes, this expands with humidity, to a point where the increased tension
causes by this swelling causes the hammer to lift of the wood. Especially
when there are no staples holding the hammer felt into shape.  You have seen
hammer heads with the felts popped off ?.  This is common in areas of high
humidity.

And yes wool felt does expand.  In my first post on this subject I mentioned
that there is a high possibility that the backtouch felt used by Yamaha,
which is "not wool felt" may not expand as much as does "wool felt" thus
giving the Yamaha more stability in this area.

I know that in different areas you will get different humidity swings that
will not show the effects of the moisture penetration as much as other areas
but in this town I live in the swing is high. No experimentation is needed
here because it is so obvious.

Regards

Tony Caught ICPTG
Australia
caute@optusnet.com.au

----- Original Message -----
From: <JIMRPT@aol.com>
To: <pianotech@ptg.org>
Sent: Friday, December 29, 2000 7:34 AM
Subject: Re: When to do it


>
> Terry, et al;
>  I have no doubt that leather tends to swell up when soaked with water but
I
> don't 'think' that wool does so. Has anybody done any experimentation on
> whether wool changes size with moisture absorption? There has been much
> speculation in this thread based on the felt changing size and I wonder if
it
> really does?
> Just a passing thought.
> Jim Bryant (FL)