When I worked for Art Reblitz I learned that you use leather for
gaskets because, if you have to take the unit apart, the leather gasket
will likely remain good, while the cork gasket will tear up causing you
to have to make new gaskets.

All gaskets should be glued to a board (using hot glue, of course),
then orange shellac should be applied to the bare surface of the other
board where the leather gasket will touch.  The boards are then
re-united once the shellac is "tacky".  The shellac may or may not be
diluted with alcohol.  In practice I have found that the shellac does
not need to be diluted and one does not have to wait for the shellac
to become tacky.  The boards will still come apart without destroying
the leather gasket until the leather is rotten after decades or scores
of years.

In a wet/dry climate, gasketed joints that are so "sealed" will allow
the piano to play full steam once Christmas and dry weather arrives.
There can be no unsealed joints!

Bill Pixley