As perhaps the first person in MMD to suggest the use of silicone
rubber as a pouch sealant, I feel justified in making a few comments.

First of all I would like to *strongly* urge all subscribers to the
MMD, especially the newer ones, to go back and search the MMD Archives.
It is easy to do using the elegant search engine provided.

 [ Thanks for the "elegant" complement, Phil, but it's really just
 [ an index, created for us by MMDer Bob Fitterman.  To truly search
 [ the MMD Archives for a key word which isn't indexed, I recommend
 [ the Alta Vista search engine, http://www.altavista.digital.com/
 [ which seems to know about practically all of the Digests from the
 [ beginning of MMD!  -- Robbie

I joined the MMD about two years ago and some of my first postings
were on the subject of pouch sealants.  (As we used to say when going
to the movies, "This is where I came in.")  I had recently constructed
a device to allow the accurate measurement of air leakage in almost any
pneumatic component, with the results displayed as cubic inches of air
per minute.  I measured and reported on the leakage/sealing efficiency
of virtually every available type of suggested sealing compound: mink
oil, Carter's Rubber Cement, egg white, silicone grease, air-curing
silicone rubber, PVC-E, etc.

At that time I reported that only two materials tested appeared to
give complete sealing: PVC-E and silicone rubber.  The PVC-E caused
noticeable stiffening in the pouch and I therefore felt it would not be
useful for pianos.  The air-cured silicone rubber, on the other hand,
left the stiffness of the pouch virtually unchanged.  At that point
I suggested that restorers may consider the use of silicone rubber as
a pouch sealant.  Consequently I believe a number of people have done
that.

It is important to clarify the term "silicone" as it applies to pouch
sealing compounds.  It is unfortunate that it can be used to refer to
two quite different materials, the first being silicone grease: a
non-hardening grease or paste not unsimilar to mink oil in viscosity.
This may or may not bleed when applied to piano pouches -- I certainly
don't wish to enter into that discussion.

The second material that the term "silicone" can refer to is air-
curing, or silastic, silicone rubber -- the familiar bathroom caulk
material that gives off a vinegar smell as it cures.  When wiped onto
a pouch and allowed to cure (about 30-60 seconds) it can no more bleed
or cause adhesion problems than can Carter's Rubber Cement.

At the time of my previous reporting I described various tests
I carried out to determine the best solvent (naphtha -- lighter fuel)
and the best dilution rates (1-2) silicone caulk to naphtha.

Whether or not you feel that the silicone rubber is a good idea, look
back in the Archives -- there's a lot of information there.  Let us not
have to rediscover the wheel every two years.

Philip Dayson
dayson@canada.com