Recrowning

[Horace Greeley]

Jon,

Gee, I don't know, this is my fourth post to the list in one day...

You wrote:

>I heard from a guy who claimed he can re-establish sound
>board crown with shims. Even if it has 3/8" negative crown.
>
>Can someone fill me in on what I might have missed in the
>last few years of trying to keep up with the last few hundred
>years?

Sure - this is something a bunch of us retired a long time ago.  It does
keep surfacing, however.

So, now that you know what my prejudice is:

While there are different methods, the deal is to disassemble the piano,
usually invert it, wedge the board up by driving wedges(!) between the
beams and ribs, then proceed with whatever repairs are in order for the
board (shimming, etc.), then glue all in place (except for the wedges, of
course).
Among the variations I've seen/tried have been keeping the piano in a
_very_ humid environment for an extended time (like a couple of months),
using hot sandbags on the inverted board which is pressed into what amount
to a custom caul which is clamped to the rim, insertion of V8 valve springs
(yes), and last, but no least, a completely freeform attempt using go bars
braced against the case which rests on the floor.

Do any of these make a difference - yes.  How much - it depends.  For how
long - ah, now there's an interesting question.

For the most part, I think this is a waste of time and energy - sorry.
There are substantive reasons for a board to lose crown/go flat, or invert.
Most of them have to do with structural deterioration of the wood as much
as the form into which it was made.  There always seem to be folks who can
sell this work - but there is so much involved to do this well - why not
just do it right and put in a new board?

The most successful job I ever did was a combination of some of the above
methods on a piano that was sold used from the San Bernardino area of
California (read desert) to the Naples section of Long Beach (on the
water).  I had a caul similar to the one described some years ago by Jack
Krefting in the Journal, and used it in conjunction with go bars, a very
humid room, and heated sandbags.  The results worked "ok" for an old L
which was used mostly to hold up family portraits.

The hot sandbag thing is actually quite a viable technique for luthiers in
the repair of stringed instruments.  They make (usually) a sand-cast form
of what they want the fiddle front/back to be, and then, after disassembly
and some humidifying of the wood, the workpiece is weighted into the form
with sandbags which are kept hot with heating pads.  The length of the
process varies greatly, two weeks is not unusual.

I think Frank Hubbard's "Three Centuries of Harpsichord Building (Making?)"
talks about this in the section on Pascal Tasquin.

So, now that I've thoroughly insulted someone somewhere, AND the red light
is blinking to tell me I'm running off at the mouth (again) - Ta Ta, for
now.

Best to all.

Horace




Horace Greeley			hgreeley@leland.stanford.edu

LiNCS				voice: 415/725-4627
Stanford University		fax: 415/725-9942