After reading the various postings regarding sealing of pouch leather
I will throw in my two cents worth.  While in business as Mechanical
Music Mfg. in Wichita, Kansas, we built thousands of wood Wurlitzer
valve blocks.  The wood was sealed with either lacquer or polyurethane
in a bath under vacuum for several minutes and then allowed to dry for
several days.

The pouches were sealed with a material straight out of the can,
brushed on the pouch after the lifter disc was glued on and then the
pouch was dusted with baby powder.  The material was Camel Universal
Cement and came, I believe, in 4-ounce metal cans.  I used to buy it
by the case.  I still have a few valve blocks treated this way.  The
pouches still seem flexible and perfectly usable.

Perhaps any one who used our valve blocks would care to respond as to
how well (or not) the valve blocks have stood up.  I do know that we
took great care and pride in producing what we believed to be the best
valve blocks available.

George Cooper