To Ray Bates and any others recovering bellows,  When the bellows
has been cleaned of the old skins, we always without failure take the
valves off, clean them in soapy water in an ultrasonic cleaner and
check them for their ability to hold air.

If they do not hold air, we then replace them with new ones.  It is
very frustrating to find, after covering the bellows, that you have
a sticky valve.  We also replace paper files with modern ones to insure
tightness.

Tony Ciuffini - The Musical Box Doctor
San Pedro, California
http://www.musicalspecialties.com/Repair/repair.html