Reading Spencer Chase's post on attaching pneumatics was an intelligent
breath of fresh air!  Like Spencer, I put restoration notes inside
instruments I work on.

It makes good sense to attach pneumatics with screws.  Broadwoods used
this approach in their beautifully made unit valve/pneumatics 100 years
ago (see MMD 2005.03.29.10 and 2005.03.30.12)

I rebuilt an Aeolian stack some 35 years back and fixed each striker
pneumatic on with two round head screws, fore and aft of the hole in
the fixed board, one accessible through a hole in the moving board
which I sealed with a disc of rubber-cloth.  This was totally effective
and allowed pneumatics to be moved slightly to achieve perfect pitman
location.

The key to any such method, of course, is the gasket material.
Broadwoods found that after a few seasons their leather gaskets, even
though of the finest quality, tended to go slack and needed nipping up
regularly.  I used high quality expanded neoprene sheet, which is still
in perfect condition, and have never had to re-tighten.  This is by far
the best material for separable gaskets, as several UK expert rebuilders
can testify.  I have also used just the right grades for valve faces
and they are working perfectly many years on.

Again I must stress the importance of choosing an appropriate material,
its quality and, as Spencer said, using it correctly.  This is not just
a matter of trial and error or vague opinion.  Knowledge of materials,
published spec sheets, experience and imagination are powerful tools.

For instance, it was clear before it was ever used that Perflex would
be poor for pouches: it's an isotropic, un-reinforced, extended
urethane plastic/elastic with relatively high hysteresis and frictional
characteristics, and almost impossible to bond reliably.  Nevertheless,
there are still excellent durable modern substitutes for today's
inconsistent zephyr skin, pouch leather and rubber-cloth, but which
would need to be ordered in significant quantities to be produced.

My main reasoning for screwing pneumatics on was, like Spencer's,
ease of future servicing.  However, implementing the system took quite
a time, and I found that years on, the rubber-cloth I'd chosen being
still perfect, I'd had no need to dismount a single pneumatic.  So
I decided to find a reliable fixing method which saves time and effort
yet allows later removal of pneumatics without damage from hot glue:
whoever would countenance having to make new sets of boards or repair
decks rather than use good originals?!

The obvious solution is, of course, to interpose like Aeolian and
Hupfeld a sufficiently strong interlayer which can be parted.  But
since today we can get neither leather, card nor glue exactly as the
original, and we want to achieve a first-time reliable and durable
result, why not use an adhesive which itself forms a gasket interlayer?
RTV proved to be ideal, and totally reversible when used as I have
described.  I also used it totally successfully for Duo-Art steamboat
pumps, which shows how strong and reliable it is.

I am, by the way, amazed that some readers still choose to confute
PVA [polyvinyl acetate] and PVC [polyvinyl chloride]!  They are
entirely different.  *Do not use* PVC, PVC-E, casein or epoxy
adhesives for any bonds which may need to be parted!  PVA, on the other
hand, is water-soluble, pH neutral and can be used safely anywhere.

Also note the difference between silicon and silicone.  Silica
(ceramics) and silicones (lubricants, adhesives, rubbers...) will
become ever more common because they are predominantly silicon, the
second most abundant element in the universe, and energy efficient
and non-toxic methods now exist for producing them cheaply from sand
without the need for oil.  Silicone rubbers are the most durable,
consistent, stable and inert over a huge temperature range, and one
of the few biocompatible materials possible to use in the human body.
When incinerated silicones become simple silicon dioxide -- fine
white sand.

With our vast heritage in Britain we are as aware as any of the
arguments distinguishing renovation, restoration and conservation.
I was born and raised in a 700-year-old house which had its last major
rebuild in 1485; and I worked with restorers of some of the world's
most important paintings.  There are two important points to be made:

First, it is why and how things are made and used -- their context --
which makes them truly important, not mere possession or market value,
which is why our still-lived-in, constantly-evolving country houses
are considered far more valuable than museums and collections.
A 300-year-old church pipe organ (relatively common here) is worth
nothing if it cannot be used reliably for worship, so most have been
rebuilt and changed through the centuries.  I have no use in my sitting
room for an immaculate, expertly-restored Duo-Art that is unreliable
and does not reproduce properly.

Second, traditional materials can be terrible liabilities!  Old
canvases were relined using corrosive wood resins and animal glues,
and removing them is today a hugely long and risky process.  Nowadays
PVA is always used.  Since pictures were for pleasure rather than
keeping in vaults, most received some kind of intervention at some time
or other.  In the past, cleaning and repainting were blithely carried
out using traditional, often toxic materials which caused significant
damage, and again undoing these ravages is enormously difficult.  Today
after cleaning and conservation with complex chemicals selected not to
damage original paint, a benign transparent isolation layer requiring
a unique solvent is sprayed on before restoration with modern pigments,
so that the process is totally reversible.  Sounds familiar...

Paddy Handscombe
Wivenhoe, Essex, UK