I've been asked for more information regarding the use of egg white
as a pouch sealant.  I'm afraid I have no more to offer but this
reminiscence might be of interest.

In the early 'sixties I was working at the London Piano Museum and we
were visited by an elderly German gentleman.  Before the Great War he
worked for one of the major Leipzig manufacturers (Popper, I think) and
his job was to ride round the area in his pony and trap, training and
supervising the outworkers.  These were women with families who worked
at home, often assisted by their older children, producing the smaller
bulk components such as note pneumatics, valve assemblies and cushion
pouches.

I asked him to describe the procedure for making the cushion pouches.
Some of the details are probably long forgotten, but it basically went
like this:-

Each operative was provided with a length of dowel, a straight piece of
piano wire the same length, a small guillotine, a specially designed
hand operated punch and a board which resembled a bed of nails with the
points ground off.

A strip of skin was cut to the correct width and wrapped round both the
dowel and the wire.  This was glued to form a long tube and the piano
wire then withdrawn to create some slack.  The whole thing was rolled
on a hard surface to compress and seal the joint and the tube of skin
was then slid off and hung up to dry fully.

It was then guillotined into sections and the hole punched.  Next,
the open ends were folded and glued.  This was the trickiest part of
the operation but was apparently carried out freehand.  The whole thing
was then painted with egg white and hung on one of the nails to dry.
The nail passed up through the hole so that the pouch hung partially
open under its own weight.

Once dry, the lower fibre washer was glued in place and the pouch
again returned to the nail where the upper fibre disc was applied.
This ensured that the glued area on the top of the pouch was kept to
a minimum and precisely controlled.

Our visitor friend referred to the pouch material as "Wurstpelle"
(sausage skin) which gives a clue as to its origin.  The more glamorous
term "zephyr skin" was probably contrived much later.  Presumably,
somewhere in the world there is still a company manufacturing this
remarkable material.  Does anyone know who, where and how?  It would
also be interesting to hear if it has any other applications.

Richard Stibbons
richard@stibbons.com.geentroep