Bill Maguire wrote in 110224 MMDigest, "I want to buy neoprene material
to make my own valve facings. ... I'm guessing I would want a closed 
cell, something resilient (memory) made with quality."

No!  That [sponge neoprene] is a poor choice of material for anything
to do with a player piano.  It either dries up and leaks or gets gooey
and sticks.  Been there, done that.

Use leather -- cow leather. 

Don Teach - Shreveport Music Co.
Shreveport, Louisiana