Capo Hardening, was: Tuning problems under capo bar

[Robin Hufford]

Steinway, for many, many years has hardened the Capo bar, using heat, as, I
believe, did other high quality American  manufacturers,  and, in the older
pianos,  they did so very effectively.  In the 60's, or thereabouts, Steinway
began to neglect this with the result that some of their newer production
exhibited problems in the treble.  The Piano Technician's Journal contains an
article, written perhaps ten or fifteen years ago, describing the hazards of
attempting to harden a Capo with heat and dealing with such a piano.  The essence
of the problem is the deleterious effect of differential heating in the plate.
The effects of this were minimized by a very rapid, intense method of heating,
which aimed at quickly  heating and hardening the surface while  containing the
penetration of heat into the remainder of the Capo.   It was performed, if memory
serves, by a professor of engineering at the school which owned the piano and for
whom the technician  provided repair services.     The article describes a
successful procedure for dealing with these hazards and achieving a useful
result.  This result was reported as an immediate improvement in tuning stability
and quality of sound in the relevant areas of the scale.
Regards, Robin Hufford

Ron Overs wrote:

> At 6:28 PM -0500 24/1/03, Farrell wrote:
>
> >Hello Ron. I there anything you can tell us about hardening the capo.
>
> Yes but unfortunately I am not prepared to publish it on the list,
> since I'm not prepared to hand a process to the major manufacturers
> 'on a plate'.
>
> >I've seen you write about that before. Is this something you do in your shop?
>
> Yes, and its a routine procedure that we've been using on all
> rebuilds since 1995.
>
> >Do you do it to all pianos? Do you have a method of testing the
> >hardness of the capo?
>
> I use a piano wire off cut, holding it perpendicular to the bar an
> hitting the wire with a hammer to check relative deformation between
> the bar and the wire (obviously this test is done at the ends of the
> bars and not where the strings contact the bar).
>
> Ron O.
> --
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>
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> Grand Piano Manufacturers
>
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