Rob I see by your web site that you are in the San Francisco area. Is this piano close to water, like a river or the ocean, because I see this a lot in Hawaii. It's a humidity problem. Moisture gets in the damper felts, and transfers it to the string. The same with the hammers. They are "wet", and when they hit the strings, the moisture transfers to the strings. Now that it is on the strings, there is nothing you can do to get rid of it. To keep it from getting worse is put in a dampp chaser. Not just in the bottom of the piano, but also up in front of the action. Willem (Wim) Blees, RPT Piano Tuner/Technician 94-505 Kealakaa Str. Mililani, Oahu, HI 96789 808-349-2943 www.Bleespiano.com Author of: The Business of Piano Tuning available from Potter Press www.pianotuning.com -----Original Message----- From: Rob Mitchell <tpa2sfr at pacbell.net> To: pianotech at ptg.org Sent: Mon, Oct 19, 2009 8:31 am Subject: [pianotech] U1 - stained bass strings 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20091019/209d42e9/attachment.htm>
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