The lively discussion regarding pouch sealing techniques is great, and not
likely to end soon.  I am dismayed however, that nobody has questioned any
of the sealants in terms of the first standard by which responsible work is
judged, that being the requirement that the technique or material not cause
any degradation of non-replaceable parts.  It seems to me this has to be the
very first goal of the restorer.  White glue, after years of indiscriminant
use, has finally been identified as an unacceptable material for
rebuilding, since removing it generally causes damage to the wood.  I would
suggest that some of the proposed sealants are even worse.

Mink oil has a time-honored reputation for eventually ungluing the pouch,
leaving behind an oily mess on the wood.

Silicone, unless I am mistaken, _does_ migrate, and will migrate across
contiguous surfaces until it is one molecule thick, or runs out of surface,
whichever occurs first.  Piano rebuilders (and refinishers) have known for
more than a decade that silicone oils and sprays are anathema to the
workings of a piano action, and those materials have all but disappeared
from our tool kits in favor of Teflon or other lubricants.

I don't like rubber cement.  It is not rubber, and it can turn to cement,
but it is _not_ a contaminant.

The proof of all this might be to treat pieces of pouch leather with the
various proposed sealants, and leave them undisturbed face up on a sheet of
glass.  Inspection after several months will reveal which ones have left
behind a residue that made its way to the glass from the top surface of the
leather.  The ones that do are unacceptable.

Doug Rhodes¶
RTT - The Piano Technicians Guild¶
Victoria, British Columbia