[ Dell Urry wrote in 100113 MMDigest :

> I wonder why pipe organ pouches have never been sealed with mink oil.

In my younger organ building years, when I was still an apprentice,
I had the chance of meeting two very old -- way up in their eighties
-- former employees of the leathers and windchests department of
Casavant Frères organ company.  These two explained to me how the
pouches on organs they made before 1947 were treated with a dubbin
made of mink oil, beeswax and naphtha.

The use of a sealant on organ pneumatic leather was very common before
World War Two.  This was the time when most pneumatic windchests were
"ventil" types only.  On those windchests the pouches commonly called
"puffers" are kept under pressure by their undersides when the stop
channel they are installed into is not pressurized.

To avoid some false pipe firing or ciphering, a spill valve is used
to dump any accumulation in the channel caused by the porosity of the
leathers.  This works also with untreated leather, but the exhausts of
the spill valves need to evacuate a large amount of air -- they become
very windy and noisy when untreated pouches are used.

That's a flaw I encounter on many organs re-leathered by my
competitors these days.  It seems to me my fellow organ technicians
lost their touch when re-leathering ventil windchests.  Or is it done
that way to save on time and money?  I would never skip dubbin leather
treatment on such re-leathering jobs.

The other type of pneumatic windchest, the Pitman action, doesn't
require any special treatment of the puffers after they're glued to
their "pufferboards", although in some cases it has been done for
implementing the rapidity of the action.  Pressure is applied to them
only when the pipes they feed are needed.  When the valve is at rest
and the stops are turned off, both the chest channel and the puffers
are at the same pressure thus no air is flowing through the pores of
the leather.  No need of spill or dump valves; no noise, too.

If any of you want to know more about pipe organ and their leather
works you are welcomed to write to me at any time.

Gilles Chouinard, organbuilder
Laval, Quebec, Canada
gcorg@aol.com.geentroep [delete ".geentroep" to reply]

 [ A short explanation of dubbin, with links, is at
 [ http://en.wikipedia.org/wiki/Dubbin  -- Robbie