Hi Rob.
I've seen it before, and, here's a shot in the dark that you've probably
thought of, I wonder if someone poured hammer softener or hardener onto the
dampers and hammers? Does the client known if someone did that?
Bruce
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From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of pianotech-request at ptg.org
Sent: October 19, 2009 12:40 PM
To: pianotech at ptg.org
Subject: pianotech Digest, Vol 12, Issue 163
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Today's Topics:
1. U1 - stained bass strings (Rob Mitchell)
----------------------------------------------------------------------
Message: 1
Date: Mon, 19 Oct 2009 11:31:52 -0700
From: "Rob Mitchell" <tpa2sfr at pacbell.net>
To: <pianotech at ptg.org>
Subject: [pianotech] U1 - stained bass strings
Message-ID: <000601ca50ea$6e137a20$4a3a6e60$@net>
Content-Type: text/plain; charset="us-ascii"
I've been working with Yamaha on this, but the best we've come up with is
that some sort of atmospheric contaminant is attacking the strings. Thought
I would try this group to see if anyone has seen the problem. This is on a 4
year old Yamaha U1.
As you can (hopefully) see from the pictures, this is a very unusual
phenomena. It looks to be some kind of ink or marker in some very odd
places. It occurs on ALL the wound bass strings under the damper felts and
at the hammer strike points. For the damper felts, the stain is exactly at
the contact point between the felts and strings. For the monochords, the
stain wraps around the string. For the bi-chords, the stain is between the
strings from the wedge. It's as if someone used ink-soaked dampers and
hammers to check for damper contact and strike point. (The hammers and
dampers themselves on this piano are normal and show no signs of the stain).
The stain is not just on the surface of the coils -- it seems to be all the
way into the grooves.
Furthermore, both the L and R strings on B1 (as well as some other strings)
have the markings smeared from the dampers almost up to the tuning pins.
And there is an every-fourth-string marking again closer to the tuning pins.
All the strings look completely normal and free of the markings below the
dampers. I tried some fine emery paper on a B1 string and the marks seemed
to scrape off fairly easily. I didn't want to try anything more aggressive
like alcohol, wire brushing or steel wool.
The customer's concern is that at a minimum, this diminishes the resale
value of her piano and at worst, might be something that would accelerate
string wear/breakage.
Anyone seen this before?
Rob
Mitchell Piano Service
(415) 994-1030
www.mitchellpianoservice.com <http://www.mitchellpianoservice.com/>
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