[CAUT] pre-stretching new string?

[Ron Nossaman]

> Hi Ron,
>     "Measurable" is not a precise word. Depends what your level of accuracy
> is. + or - what? Under what circumstances?
>     The experience I refer to isn't just noticing how strings go flat over
> time. It's also knowledge of how materials behave. Most processes like
> string stretching (deformation under load, if you like) happen in a
> parabolic curve, with more rapid change at the beginning, and more gradual
> change approaching and never quite reaching a limit over a longer time. I
> have trouble with the notion that piano wire is different. How rapid at the
> beginning and how gradual later? The more the process is "front-loaded," the
> more impression one might get that "it all happens instantly" and it could
> be "true enough for most applications" but still not absolutely true.  I
> first heard that "piano wire doesn't stretch" (more or less what you quoted)
> over 25 years ago. I've been keeping that in mind as the "official
> scientific opinion" ever since. But I haven't been able to digest it yet.

Hi Fred,
I expect that is precisely why the information was worded that 
way - to avoid making an absolute to the molecule statement 
that steel doesn't creep at all, not ever, even a little bit. 
That's not what they, or I said. I doubt there is anything on 
this planet that is absolutely dimensionally stable. Whether 
or not the expected dimensional drift will be measurable, 
noticeable, annoying, or catastrophic, is the question. I've 
looked around, and asked what engineering type folks I know, 
for some reasonably authoritative source for low temperature 
creep information on steel. Nearly as I can tell (not 
absolute, note) it's so minor that nobody seems to be 
concerned enough about the amplitude of the phenomenon to 
measure and record it - if it is indeed measurable. High 
temperature, certainly. I easily found dozens, if not hundreds 
of references to high temperature creep, but only the two I 
quoted for room temperatures.


>     My take is that some of the pitch drop could be in the coils, some could
> be in wood crushing, some in "conforming to bearing points," and some could
> be in string stretching. I don't think any of us has full evidence to say
> how much or little results from which. 

No one has said different, have they? None of us will ever 
have full evidence on anything. It's not possible, to my 
incomplete knowledge.

There, a closed self reference. Get out of that one. <G>

Seriously though, I said what I think to be the case, and I 
indicated that it was what I thought to be the case - not an 
irrefutable absolute truth.


> We're probably all right and all wrong
> to some extent. 

Like we're all partially and incompletely right, and partially 
and incompletely wrong. What we're discussing here is what 
percentage of which, on whatever the current question is.


>I do know that new strings drop in pitch over time on old
> instruments with zero to negative bearing, in my experience (meaning wood
> crushing probably wasn't a significant factor there).

Wait a minute. We did this already. Why would wood crushing 
not be a factor with negative bearing? Hasn't it already been 
determined fairly reasonably that soundboard rise, or fall, 
isn't a significant (there's that word again - not absolute or 
exclusive, even if measurable) factor in pitch change? Isn't 
there still lateral pressure on bridge pins? Isn't there still 
longitudinal pressure on tuning pins? Haven't we all seen 
bridge pins that had been pushed back by string pressure 
enough to produce a visible gap between the pin and the side 
of the hole? Haven't we all seen in removed pinblocks how 
deeply indented the block is where the edge of the plate 
flange sat, and how detailed an impression of the plate 
irregularities is pressed into the surface? Haven't we seen 
tuning pins (lots of them) that had a very noticeable gap 
behind them where string tension through the years pulled them 
toward the hitch pins? How is that not wood crush, and how 
could that not be a very *major* factor in long term pitch drop?

Be a skeptic, by all means, but hopefully with an eye toward 
accumulating better data, rather than discounting obvious 
evidence that doesn't fit the preconception.

Just an observation of evidence needing processing.
Ron N