Craig Brougher writes in 990305 MMDigest:

> The best way to remove that [old leather] is first by scraping,
> and then wetting it, letting it soak a short while, and then just
> rolling it off.  You can get 100% of it off that way.

In my restoration of old mechanical organ bellows I use an old
electric steam iron at moderate heat, to remove all vestiges of old
leather et al, as well as much old glue.  Sometimes I put a damp
cloth on the part and iron lightly over it.  The cloth will soak up
the extra old glue.  Perhaps this can be used on pneumatics as well.

Frank Metzger