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MMD > Archives > December 2001 > 2001.12.02 > 04Prev  Next

Rebuilding Valve Pouches & Pillow Pouches
By Craig Brougher

Reading the offerings about repouching and pillow pouches (puff
pouches) as well as zephyr skin material, I was surprised to learn that
Miguel waited for his leather pouches to dry and then pouched them with
a heavy marble.  He said:

> Usually I make the depression in the pouch before I glue it into the
> pouch hole.  This time I glued the pouch without making the depression,
> and after the glue dried I stretched the pouch leather with a round
> marble, big enough just to enter a small part of it, so all the 88
> pouches took the same size."

I just wanted to warn amateur rebuilders never to do it this way.  One
property of leather happens to be that it both stretches and shrinks.
If you stretch leather while it's wet and leave it stretched until it's
dry, it will stay stretched but it will get hard (depending on the
tanning process used).  If you just stretch leather while it's dry and
leave it, then, depending on the weather, it will return gradually back
to its original size over a long period of time.

We have all broken in a tight pair of shoes that we wore continuously
for awhile, put them away and didn't wear them for a long time, then
tried to wear them again and noticed that they were uncomfortably tight
again.  Player rebuilders have, on occasion, come across actions whose
pouches had shrunk, due to the pouch leather returning to its original
size.  It's best to dip the pouch while placing it.  Putting a stretch
in dry leather is going to be temporary, and I hope that hobbyists
understand that.

Another thing to know is that unless bugs have gotten into old zephyr
skin, it's still fine.  It won't rot.  Zephyr skin is permanent.
However, something in zephyr skin attracts certain moth larvae, it
seems.  I don't know another reason why I have never found pouch
leather with bug holes in it, but lots of zephyr skin I have found
eaten up.  It also doesn't bode well for its future in the player
piano, either.  That means that you could replace old zephyr skin with
new, perfectly tanned zephyr skin, and the same thing could happen to
the new stuff a year from now.

Regarding pillow pouches made of pouch leather: I would encourage using
it, rather than zephyr skin, but use only the very thinnest fringe
material, no thicker than .008" [.2 mm].  That's when you need to have
on hand a number of extra-thin skins.  Also, make sure the ends of the
"pillows" are not pinched off too deeply, cutting down the power they
should have.  The pillow pouch gets its power by being able to balloon
against the pouch deck, giving it twice the rise of a normal pouch in a
well, in the same length of time.  This can operate in valves requiring
more pouch travel in the same length of time, and they can drop quickly,
giving better repetition in certain applications where those factors
are needed.

I would also suggest using "Dow 111 Pure Silicone Grease", thinned, as
the sealer, and then put talcum on the leather.  Pillow pouches have
to be quite tight.  When rubber cement is used as the sealant, it
becomes stiff in about 20 years time, and will no longer repeat as
well.  I have seen small 1" pouches so stiff with rubber cement that
they would hardly work at all.  And rubber cement will not preserve the
pouch, either.  Rubber cement just temporarily seals pouch leather, at
the expense of good repetition several years down the line.

The last issue I would like to take with other natural oils and greases
is that all normal grease is lighter than water, it is slightly acidic,
and it creates a vapor pressure inside every player it is used in.
This will eventually cause corrosion and verdigris on metal parts like
valve stems and plates.  Besides its own tendency to vaporize slowly in
low pressure, all animal grease -- like Neatsfoot oil and mink oil,
lanolin, and bear grease -- attracts bugs, and slowly saturates the
wood wherever it contacts wood.  I strongly advise against it.  Use Dow
Corning 111 Silicone Grease to prevent all of these properties from
ruining your rebuild.  But remember that you cannot glue things to
leather sealed in this fashion, so if you need a lifter disk mounted on
the pouch, put it on first, and apply the sealing solution carefully,

There have been many otherwise conscientious, careful, thorough
restorations ruined 10-20 years down the line by using the wrong
sealants, or procedures, such as pouching after the glue has dried.

Craig Brougher

(Message sent Sun 2 Dec 2001, 15:23:46 GMT, from time zone GMT-0800.)

Key Words in Subject:  Pillow, Pouches, Rebuilding, Valve

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