Hello,  After reading D. L. Bullock's submission on the use of RTV
I could not stop myself from giving my opinion.

Everyone who has restored instruments that others have "restored",
patched or screwed up in other ways, has likely encountered silicone
used in ineffective and or destructive ways.  I restored one piano
that comes to mind that had so much glop of various kinds that I spent
more time dealing with the effects of the glop than the rest of the
rebuilding process.  Silicone was dripping off places it never should
have been and oily residue was left from some sort of plasticene clay
that had been used where silicone could not be smeared on.

Any material can be used to the detriment of a fine instrument.
Probably as much damage has been done with hot glue as with any other
glue, but it is true that [hot glue damage] is usually reversible.  The
point that I would like to make is that it is not the material chosen
but the way it is used.  Paddy Handscombe has clearly considered the
consequences of the use of RTV silicone.  His proposed method of
providing an isolation film assures that there will not be any problem
using other adhesives in the future.

It is ridiculous to think that the materials used by the original
manufacturers were the best possible and that nothing today is better.
There are some incredible adhesives made today which need to be
carefully considered, especially when the classical ones become
unavailable.

The concern about deterioration of silicones and the releasing of
caustic agents is unwarranted if good materials are used.  Silicone
rubber is one of the most stable materials available today.  If a good
grade of neutral cure RTV silicone is used, it will outlast everything
else in the piano and will not damage anything.  It does not deteriorate
except in extreme conditions that would destroy the piano itself.

My main concern when restoring a pneumatic instrument is the fact that
materials, which were common when the instrument was made, are not the
same today.  In the 1920s manufacturers had their choice of many
suppliers of pneumatic cloth and many different grades.  Today you get
what you can get, which is very limited.  I have bought the best and
have seen it to start showing signs of wear after just a few years.
I have had better luck, so far, with synthetic materials.

My preferred method of making it easier to restore in the future is
to attach the pneumatics with screws, the way there were often attached
in the finest instruments.  It is quite a lot of extra work but no one
will have trouble removing the boards without damage, unless they don't
figure out that the screws are there and even the least conscious
restorer should discover this after removing a few of them.

It is most likely to be the pneumatic cloth that will require replacing
before anything else if a restoration is done today.  If the cloth
fails in 10 years it is going to be much more difficult to remove
pneumatic boards that have been recently glued with hot hide glue.
I don't like the smelly mess that heating boards makes if you do this
to remove them.  It is possible that restorers of the future might not
be familiar with these methods and may do considerable damage.

When I work on an instrument and use unconventional materials or methods,
I like to write a little note and put it in the piano in a place where
it is likely to be found, describing what to expect.

Best regards,
Spencer Chase