steaming

[David Stanwood]

Dear Dave,

Imagine a single wool fiber. Crumple it down and it springs up again 
repeatedly to 90% of it's original straightness.  Wool fibre has the highest 
regain of any fiber man made or nature made.

Now heat that fiber up and it softens like plastic.  Now press it down
and it doesn't come up to 90% maybe only like 30% or 40% or less depending 
on how much heat and pressure... This is like hot pressing a hammer.

Now hit it with the steam and it springs back to 90%
The steam simply releases the hot pressed effect.

Hammers that have been hot pressed gain additional density at the expenes of 
regain and resiliency.  Steam releases the effect of the hot pressing and 
causes the fiber to puff out, the air spaces in between to open up, the 
density to drop, ant the felt to become softer and more resilient.

Heat and water are the activating agents.  Steam is nice because it puts 
very little moisture into the felt and it drys out in a very short time and 
the effect is long term.

David C. Stanwood

>From: "Dave Nereson" <dnereson@dimensional.com>
>Reply-To: pianotech@ptg.org
>To: <pianotech@ptg.org>
>Subject: steaming
>Date: Tue, 5 Jun 2001 03:05:13 -0600
>
>Welp, I checked all the archives (I'm pretty sure) on hammer steaming, and 
>the gist was that steaming is meant to soften, not harden hammers (which I 
>surmised), although no one said that explicitly -- the general reason given 
>for the process was to "improve the tone".   And there never was a definite 
>answer as to what happens to the tone when the moisture from the steam 
>evaporates from the hammer.  Does the hammer stay soft or does the drying 
>cause the wool to shrink and get hard and have a "bangy" tone again?  I 
>didn't see any definite answers in the archives, unless I'm missing 
>something.  I have steamed hammers that were extremely hard and it did 
>soften down the tone.  That was a while back and the customer hasn't called 
>back to say it's strident again, but then many piano owners don't notice 
>it's out of tune until it's really bad, either.  --Dave Nereson, RPT
>

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