In the 110612 MMDigest, Mark Ritzenheim said:

> The 12 lb., 14 lb., etc. weight of hammers refers to the weight of
> the sheet of felt from which the set of hammers is made.  A 14 lb.
> sheet will be thicker than a 12 lb. sheet, obviously.  Also, the
> entire sheet of felt is not used in making one set of hammers.  This
> is still a legitimate way of referring to hammer sets, because a
> heavier weight will also make a heavier hammer.

I agree with Mark that we are talking about "the weight of the sheet of
felt from which the set of hammers is made".  I do not agree, however,
that "a 14 lb. sheet will be thicker than a 12 lb. sheet".  And I do not
agree that "the entire sheet of felt is not used in making one set of
hammers," nor that "a heavier weight will also make a heavier hammer".

Felt is made of hair (wool), and with the same amount of wool (thus
with the same weight) one can produce different thicknesses of felt.
And conversely it is possible to produce sheets with the same thickness
but with different weight.  A higher weight means more wool used, more
labour involved (both causing more costs, which means a more expensive
product), and given the same thickness (possibly, but not necessarily)
a harder felt.  It's a compromise between the type and quality of the
wool used, the wanted quality of the felt regarding the proposed use,
and of course the piano makers wishes and calculations.

By the way, a sheet of felt for hammers does not have just one
thickness over all but follows the proposed dimensions of the hammers,
so such a sheet is thicker on one end (the bass side) an gradually goes
down, all the way, to the highest descant note, where it is quite thin.

And, in order to get at least the same quality of felt from the lowest
to the highest note just one sheet is used to produce a complete set of
hammerheads, normally including some spare hammers, thus widening the
range of pianos that these sets can be used for.

Apart from that, the split between copper-wound bass strings and plain
blank descant strings, always somewhat a problem, would be widened,
since if at the weakest point two different felts would meet that would
not make life easier for the tuner.

A heavier weight of the sheet of felt is not guaranteed to cause a
heavier hammer.  A hammer consists of more than just felt -- some wood
is involved, often two layers of different felt are used, impregnation
is common, tacks may be used, and so on.  The weight of the felt is
important in relation to the size of the piano and the way the
instrument is proposed to be used.

But weight is just one of very many components responsible for the
tonal quality.  Proper caretaking, regulation and tuning/intonation is
by far more influence than those minor differences in weight, as is the
room in which the instrument is played.

Nowadays lots of information on this subject also can easily be found
on the Internet.

Jan Kijlstra
The Netherlands