pitch raising

[A440A@AOL.COM]

 les  writes:

<<  My question is regarding the
"stretchiness" of strings on ordinary pianos needing PR's of 50 cents or
more, and better pianos which need less adjustment, but may not have been
tuned in two-four years. >>

Greetings, 
    There is more to this than the strings.  They are  the power in the 
entrainment equation, but other variables are involved.
   The "change/loss of stability" to the strings is going to occur primarily 
at the bends, since a100 cent raise moves a piece of new string  into the 
radius found at the agraffe, and to a lesser extent, at the tuning pin coil 
and the bridgepin.  This deformation is one factor in stability, but is  
easily resolved by a light tapping of the string in the direction of the 
bend.  
    The entire rim assembly is going to see additional pressure from the 
soundboard.  If you add a lot of tension, there is going to be a change of 
stress somewhere in the wooden structure of the instrument, and that is going 
to take time to fully resolve itself.  How much? I have no difinitive answer, 
but the more crown and downbearing pressure, the more influence the wooden 
structure has on stability.  A flat board doesn't seen to have as long an 
adjustment period.  
   What to tell the customer about a 100 cent flat piano?  I say two passes, 
(one fast and the second very careful) will be needed on the first visit, 
(currently  $150 worth of work, and I check the plate bolts and stuff as part 
of this).  Then, anywhere from two or three weeks to two or three months, 
they may want to tune it again, after which they are ready to resume a normal 
tuning schedule.  
   It has often been fortunate that I left the expectations this loose,  
sometimes the piano will sit there singing decently for a season, and other 
times it will head for outer space in a month or two.  Preparing the customer 
is the essential part of the job. 
REgards, 
Ed Foote RPT