Ken Schweim asks about using bathroom caulk in his work.  I'd be leery
of that.  I think that many bathroom caulks have a mildew inhibitor in
them, and I don't know what the effect of that would be over the long
haul.

There is a lot of good information on various silicones in the MMD
Archives.  Look in the subject index under "silicone" and also under
"Dow."

I have been using flowable silicone to seal the thin kangaroo leather
which I have begun using in place of tan pouch leather and thin rubber
cloth in many applications.  The kangaroo is virtually untearable,
while you can tear the tan pouch leather of the same thickness with
two fingers.  But the kangaroo does need sealing for pouch or pneumatic
use.  While flowable silicone is runny, unlike regular silicone, I thin
it still further with naphtha.

When I first began using the silicone-sealed kangaroo, I made the
mistake of sealing the total length of the strips I had cut to use
in covering finger pneumatics, applying the sealant to the hair side
(do kangaroos have hair?) of the leather from end to end.  I found
that, although I had no problem gluing the leather to the pneumatic
boards -- in fact the kangaroo is a delight to glue and to work with --
I could not glue down the overlap, kangaroo-to-kangaroo, at the hinge
end of the pneumatic board.  The silicone just would not take glue.
Now I cover one end of the kangaroo strip with masking tape for about
a half inch (or whatever the overlap will be) before applying the
sealant.

The jury is still out on the question of the life span of a pneumatic
covered with kangaroo vs. a rubber-cloth-covered pneumatic.  It has
only been two years with the kangaroo.  The rubber cloth in the same
application lasted about seven years.  The next time I have to re-cover
the pneumatics on the snare drum action, I will use kangaroo.  That
will give faster test results, because rubber cloth in that application
lasts only a little more than a year before it begins to produce
somewhat sluggish action.

Matthew Caulfield
Irondequoit, New York