Twist GC bass strings?

[John Delacour]

At 15:29 01/09/01 -0700, Diane Hofstetter wrote:


>I'm just about to install my first set of Danny's strings in years.
>
>I forget, my "oldzeimers" is acting up again, I don't need to twist them, 
>right?


I write as a restorer of 27 years standing and as a commercial bass string 
maker.

My answer is that you should twist them and I'll give two reasons:

1.  When the stringmaker stretches the steel core on the machine between 
the chuck and the hook, the wire is "flat", that is to say not twisted.  It 
would be possible to pre-twist the wire and there may even be some 
masochistic stringmaker somewhere in the world who does so, but I'll deal 
with this question in a moment.  The stringmaker next proceeds to wind on 
the copper covering wire.  The thicker the covering wire, the harder he has 
to pull the copper as it is going on, in order that the wire may wrap 
itself tightly round the steel core.  This tension is applied firmly and 
evenly until the end of the second flattened portion of the core is 
reached, at which point the wire is broken off.

The tension applied to the copper is, of course, less than the elastic 
limit of the copper wire;  the wire is therefore elastic and stretched, 
having the potential to restore itself to its natural length.  At the point 
where the copper encounters the perimeter of the steel core it is suddenly 
forced to change direction and the effect of this is to compress the under 
part of the wire and stretch the upper part _beyond_ its elastic limit.

The wire, which was soft and pliable through the stringmaker's gloved hands 
is now more brittle;  its cross-section is no longer round but rather 
egg-shaped with one side of the egg slightly flattened against the 
steel.  The lesser diameter of this egg is say 8% less than the original 
diameter of the soft round wire.  But in spite of the trauma the copper 
spiral has undergone, it retains some on the tension that was applied and 
is trying to unwind.  This it cannot do because it is gripped at each end 
of the steel by the flattened lengths of the steel and the ends of the 
steel are gripped in the chuck and the hook of the machine.

What happens when the string is released from the chuck is that the 
residual tension in the copper, now free to exert itself, twists the steel 
core until the opposing action of the steel balances this force.  This 
twisting (ie. unwinding of the copper) is clearly observable by the 
stringmaker.  The actual degree of twist will vary according to the 
relative thickness of the copper and steel wire; the thinner the core, the 
less it will resist the twisting force of the copper.

Now this release of tension in the copper needs to be restored.  A properly 
made string will not buzz even if the technician installs it without 
twisting, but nevertheless the copper will not be as tight as it should be, 
not as tight as it was wound by the experienced stringmaker, and AT LEAST 
that twisting that occurs on releasing the string from the machine should 
be restored to it.

2.  To be sure of regaining the lost tension, at least one whole turn would 
need to be applied, but experience shows that the tone of a (new) string 
will actually be improved by further twisting.  I personally give at least 
two full turns to the thinnest strings and at least one full turn to the 
thickest.  The great makers (of the past) vary in their practice but many 
of them did roughly the same and after 120 years their strings still sound 
good.

I don't believe this increased brilliance of tone can be explained simply 
by the fact that the twisting tightens the winding, though this is 
obviously a factor.    There are many contributory factors to piano string 
tone and the most obscure of these is at the molecular level, for which 
there is no exact science.  When a replacement bass string is first 
installed, it will rarely sound as good as its neighbours, provided these 
are in good order, and the difference can sometimes be so great as to lead 
one to suspect the quality of the new string.  After two or three days and 
one or two tunings, the difference will be scarcely perceptible.  After 
eight days the new string will either match its neighbours perfectly or 
exceed them in tone quality.  Any experienced tuner will recognize his 
phenomenon.  The cause of it lies in the very gradual realignment of the 
molecules in the steel and copper wire to accommodate to their new 
stretched state, that same realignment that leads to the lowering in pitch 
of newly-installed strings.


Finally, I said I would say a word about the possibility of "pre-twisting" 
the cores before winding.  Certainly this would do no harm, but from the 
stringmaker's point of view it is not only a waste of time but rather 
pointless, since the technician who buys the strings will either know what 
he is doing or not and no amount of molly-coddling is going to improve the 
work of a ham-fisted technician.  I have one customer with a shop 
locally.  Whenever I visit the shop, I like to hear the strings we have 
made and judge the results in different pianos.  On every set he installs 
there will be dark marks where the copper has been handled.  Every time, I 
repeat my injunction to him and his son NEVER to touch the copper and 
either learn to string without touching it or else wear gloves.  He will 
not learn because he belongs to that superior cat-like breed of technicians 
whose hands never sweat even in the summer!

JD