Hi All,

About a week or so ago, I asked Durrell Armstrong if he would
consider writing an article about Player Piano Bellows Cloth
for the Player-Care domain. He said he'd be happy to do so.

After receiving the article, I thought, "Why not share it with
all the folks in the MMD too?" I hope you all find it as
interesting and informative as I did. The article is just below.
The web page can be viewed at:

    http://www.player-care.com/b_cloth.html

 ---- begin forwarded article by Durrell Armstrong ----

                BELLOWS CLOTH FOR PLAYER PIANOS

There are basically three grades of the rubberized bellows cloth used
in player pianos; the heaviest for the bottom pumps; the lightest for
the 88 or so "key" bellows, then a medium grade for everything else.
The everything else would include the pneumatic motor that turns the
music roll and its governor bellows which keeps the speed running the
same tempo, no matter how slow or fast the pumping.  Then you have an
automatic tracking bellows on some players which keep the roll running
straight. If there are any bellows to operate the soft, loud, or
mandolin function, these also use the medium grade cloth.

The medium grade of cloth is usually the same as the lightest cloth
doubled to itself, with the rubber in the middle, with one side dyed a
color.  The lightest cloth just has an airtight coating on one side.

The heaviest, pump cloth is always a combination of two types of heavy
cotton, with the rubber in the middle.  The outer layer of cloth is the
heavier of the two, referred to as a "drill" cloth, and which is dyed
some color.  The inner cloth is a cotton "twill" cloth which has been
bleached and a light fuzz raised on the cotton, from a brushing action.
Even though no one will see the side that will be glued, it must be
bleached.  The reason is that to use, what the industry calls, "greige
goods", which is neither dyed or bleached, but instead a dirty,
slightly yellow color, it would be disaster when you tried to glue it.
Cotton shrinks when water hits it.  When it has been dyed a color or
bleached, the process takes out most of the shrinkage.  But if two
layers of cotton were joined together, with one of them still able to
shrink from the water content of the glue, it would want to curl away
from the glued edge of the bellows board almost immediately.

The "fuzzing" of the glue side of the pump cloth will store up more of
the glue and make it easier to work with, because it won't slip around
as easily or slip back to the corner where there is resistance to
turning and a loop might develop. There can be too much fuzzing-- so
much that the cloth soaks up all of the glue that you can lay on the
edge of the bellows board, with none left over to go completely through
the weave of the cotton and bond with the rubber layer.

The rubber used to produce the various grades of bellows cloth in the
1920's, and before, was and still is referred to as Natural Rubber.
This was before the age of synthetics.  Substitutes, such as Neoprene
did not have a track record to verify its longevity.  Some form of
Neoprene compound was used as a rubber substitute in the making of
replacement bellows cloth until well into the 1960's, when even the
best grades of Neoprene, were shown to have a life expectancy of no
more than thirty years.  At this time, some of the original material,
which was now going on fifty years, was still holding up.  In the final
summation, it could be proven that Natural Rubber could last longer
than any synthetic substitute.  As with the Neoprene coatings, there
were different grades of quality, with the lasting grades always
costing more.

By 1950, the quality of the Neoprene coatings used in making
replacement bellows cloth had sunk to an all-time low. With such poor
quality, it quite often was better to leave the original material in
place rather than replace it with a product that had a life expectancy
of one or two years.  This was largely the result of indifferent
suppliers, more interested in profit and competition with others, who
asked for the cheapest coating of Neoprene.  Of course, the
manufacturers cooperated by loading the Neoprene coating down with
clay filler and making the cheapest product possible.

In the early 1950's, Player Piano Co., of Wichita, KS went into
business with the motivation of improving the quality of bellows cloth
and tubing, simply to fulfill their own needs for lasting restorations.
With a surplus of custom made bellows cloth, evolving as a supplier,
rather than a user, was inevitable.

In the late 1970's, Player Piano Co. was the first supplier to switch
to using the best grade of Natural Rubber in all types of bellows
cloth.  Examination of the bellows cloth used by Aeolian Company was
of particular interest, because there were many examples of Aeolian
products around (now fifty to sixty years old) exhibiting the Natural
rubber was still "live".  Other examples of other player actions
produced in the 1920's had shown that the Natural Rubber coating was
crystallizing or had become totally hard.  What had Aeolian done
differently?  It seems that in their quest for excellence, Aeolian had
been willing to spend more money in the coating of their bellows cloth.
Specifically, it was in the cost of the "Plasticisors" that were added
to the sap of the rubber tree.  Permanent plasticisors cost four times
as much as the cheaper types of additive.

Natural Rubber is recognized in the industry as having a better "hand".
The term of the "hand" refers to the feel of the rubber as being soft
and without undue resistance to folding. The hand is determined by what
is called the "durometer" of the rubber. Durometer is the scale of the
softness to hardness. All rubber must be cured after it is applied to
the fabric. This is done by heat. Before the curing heat is applied,
the substance is like chewing gum: sticky and without much recovery
from stretching. The application of heat allows the metamorphosis into
rubber.  Rubber can be over-cured or under-cured. Just the right amount
of heat for the product has to be predetermined.

The total thickness of the lightest pneumatic cloth is in the range of
.007" to .009" (three sheets of ordinary writing paper that you type
letters on, would be equivalent to a thickness of .009") The total
thickness would depend upon the thickness to the cotton cloth to start
with.  If Nylon fabric were used instead of cotton, the total finished
thickness could be brought down to .005" using the thinnest nylon
cloth to start with.

Thickness of pneumatic cloth also is determined by the method in which
the rubber is applied to the cloth.  If it is "calendered" it means
that the rubber coating is applied to the cloth by being transferred
by a roller, such as ink is transferred by the rollers on a printing
press.  If the spreading method is used to apply the rubber to the
cloth, it means that the cloth passes under the reserve of rubber and
in effect works like a squeegee, which can be regulated down to the
barest minimum, but still resulting in an airtight coating.

The best method used to make pneumatic cloth is to use the machine
known as the spreader.  This method eliminates pinholes, presuming that
a fine weave, first class quality of cloth is being used.

As the pneumatic cloth is wound up from the spreader, the rubber
coating is uncured and sticky, so it must be dusted with corn starch
to keep it from sticking to the back side of the previous round of
cloth.  Remember, that at this stage, the uncured rubber is still soft
and malleable, and so it leaves a cloth imprint into the surface of
the rubber coating, although it will not stick because of the dusting.
This is actually an advantage in the finished product because it allows
a better glue bond at the lap-over on the hinge end of the pneumatic.
If the surface of the rubber coating were to be perfectly flat and
shiny, the glue could not adhere as well without this roughness of the
cloth imprint.  Goods could be produced without the need for the
dusting with the corn starch, but the material would have to either
pass between heated rollers to cure before winding, or else have a
plastic insert inter-wound, to separate the surface of the uncured
rubber from the cloth until it could be heat cured.  In this case,
after the curing, the plastic liner is simply backed out of the roll
of the cloth, but it leaves a slick finish to the rubber.  The corn
starch cannot be scrubbed off the rubber coating after curing.  Even
though an uneven dusting of the corn starch, can be unsightly, it
doesn't affect the quality of the rubber.

The wear factor in the use of polyurethane coating in place of Neoprene
or Natural Rubber was actually due to the Nylon fabric that was coated
(with products named "Numalon", "Bilon", or "Polylon"). While a
Polyurethane coating is cheaper than Neoprene or Natural Rubber, it
is unstable unless it has just the right cure to prevent the
composition from breaking down and the catalyst from working out; in
this case, the coating looses its elasticity and gets gummy, although
the weave of the nylon cloth doesn't break down, and holds it together.
The wear and aging factor of nylon cloth as compared to cotton, is
about ten times as durable as cotton.  So a Nylon pneumatic cloth,
coated with the best grade of Natural Rubber would result in the best
material possible.

Player Piano Co., Inc. of Wichita, KS now has the Nylon pneumatic cloth
available.  It sells for less than half the price of traditional cotton
pneumatic cloth.  But for the purists that must use only the hot hide
glue, Nylon pneumatic cloth cannot be used; it takes a special plastic
or PVC-E glue.

Written by Durrell Armstrong, owner of the Player Piano Co.
704 Easy Douglas, Wichita, KS, 67202-3593, Tel. 1-316-263-3241

 - - - - end quoted article - - - - -

Note: Craig Brougher has perfected the process of gluing nylon to
      wood using hot hide glue. His process can be read at:
      http://www.player-care.com/hideglue.html#nylon

Musically,

John A. Tuttle

 [ John,  Thanks for sharing this with us.            -- Jody