Understand that the pouches used for operating the valves
in a player piano never have to travel more than about 1/8".
That's 0.125". That's because the valve only travels 0.040"
at most, and there should be 1/16" of free space between the
valve button and the pouch (in it's relaxed position -or
dished position) when the pouches are new. A dishing tool
will set the dish of the pouch at 1/8" (in the center). So,
the total travel of the pouch is almost 1/4", or 3-4 times
more than what is actually required to make the valve function.
(Side note: Over time, the pouches will conform to the
valve button on their own. So, within about a year, it
will appear that there is no free space between the
button and the pouch.)
The problem with the synthetic material that Player Piano
Co. sold had nothing to do with porosity. The problem was
that it suffered from hydrolysis. Within a relatively
short period of time (usually less than five years), the
material got brittle and cracked, making the pouch useless.
Another way to look at it is that it was chemically unstable,
and it attracted water molecules. Had it been inert -as was
advertised by the manufacturer- it would have lasted for
many decades -perhaps forever.
As for the contact-type cement (or plastic glue) that was
used to glue the pouches in place, I've had more than my
share of experience with the product. I found that salon
grade Acetone (100%) worked the best to remove all traces
of the glue. But, it sounds like you have removed enough
of the glue to make gluing with hide glue possible. I would
test it to be sure.
Lastly, remember that the valve button is in the center of
the pouch well, and that the button, when at rest, does not
actually go into the well. The button must always be set so
that it is ever so slightly above the level of the pouch
board. Here's why -and to my knowledge this is not written
in any books, but should be-. Consider that we have a flexible
membrane that is NOT dished, glued over a can of any size.
As long as the air pressure on both sides of that membrane
are identical, the membrane will not move. But, as soon as
the pressure on one side or the other changes, the membrane
will move in the direction of least resistance. So, if we
increase the pressure inside the can, the membrane will move
outwards towards a lower pressure. This is the primary principle
which allows a player piano valve to operate.
Now, lets look at the pouch in the player action. At rest, there
is an equal amount of vacuum on both sides of the pouch. So,
wherever it is most comfortable 'resting' it will stay in that
position. That's why we dish the pouch. So it rests at a point
which is below the level of the pouch board. The reason we must
dish the pouch is because we are NOT going to try to 'stretch'
the leather by changing the air pressure. We are merely going to
'tell' the pouch to move to a position which is opposite of where
it is at rest. In other words, a position which is opposite of
the dished position. Think of it as turning the dish upside down.
I won't go into the physics with regards to the amount of force
exerted by the changing air pressure, but it is more than
sufficient to change the state of the valve even at a difference
of just FIVE (5) inches of water vacuum.
For detailed data on pressure and vacuum, see:
Lastly, it should be mentioned that 'over-dishing' a pouch will
also cause problems. That's because the leather has a natural
reluctance to being moved at all. After all, it is a solid, and
if left to sit without being used, it will develop a 'memory'
in the dished position. If that happens, more force (or a higher
level of vacuum) will be required to get the pouch to start
moving, since it must first overcome the force holding it in
place. That's why it's very important to use a player piano with
leather pouches quite a bit during its early years. As explained
above, the pouch will conform to the button over time. So, it's
'at rest' location in the well will eventually be just a few
thousandths of an inch below the position of the button, when it's
I hope this clears things up.
John A Tuttle
This reply will be used to create another web page at Player-Care.
On 10/11/2010 2:27 PM, Paul Masters wrote:
> Below is the result of your feedback form. It was submitted by
> Paul Masters (email@example.com) on Monday, October 11, 2010 at 14:27:44
> realname: Paul Masters
> email: firstname.lastname@example.org
> email2: email@example.com
> address: 1600 Yellowstone Ave.
> city: Lewisville
> state: TX
> zip: 75077
> plus: 2460
> country: USA
> phone: 972-966-0344
> comments: Hello:
> I have been searching the WEB for a suggestion to this problem. Many
of the pages end up at your site where you offer eMail help.
> This is an upright piano with a Standard player action.
> When I purchased it 40 years ago, I was told that it said Wurlitzer on
it somewhere. I have been over most of it and have not found any indication
of the make. Also, according to my research at that time Wurlitzer used
their own player action.
> I played it a lot for a few years and it developed a few problems. So I
decided to rebuild it. The pneumatics and bellows appeared to be in good
shape, perhaps they had been redone before I bought it.
> I know enough to be dangerous. I read a number of books and articles on
rebuilding players and pianos. Fortunately for me, it appears that the
Standard is about the simplest. My father was a piano technician.
Unfortunately for me, he wouldn't teach me anything about piano repair.
He didn't like players and wouldn't have anything to do with them.
> I rebuilt the primary and secondary valves.
> At the suggestion of the parts supplier, I didn't use leather for the
secondary pouches. They suggested a plastic item that was more flexible
and should last longer. They were attached with 'plastic' glue. After
completing the work, the action did not work. All the keys would 'depress'
when using a vacuum source, but nothing would happen when it was pumped and
a roll was played. I called them about this and they said that they had
found that the plastic was porous and therefore would not work.
> All that was 20 years ago. Now I am retired I have gotten back to the
project. (A lot of other things came up in the interim!) I have the leather
pouches I should have used in the first place.
> The situation:
> There was no problem scraping off the old leather 20 years ago as
hide / hot glue had been used. However, it was much more difficult to
remove the 'plastic' clue. It was still pliable and didn't want to come off.
Fortunately it hadn't 'gone into the wood' like Elmers.
> I asked around and a person at Lowes suggested using 'Goof Off'. I tried
that, which seemed to work, but as I knew from using it before, it liquefies
the glue which in this case mostly just thinned out the glue and made it more
difficult to remove.
> I happened on an instrument repair shop which was only for brass instruments.
But talking with the person about my problem he said that he had worked with
someone who repaired guitars and that person used hot vinegar to remove Elmers
clue. I tried that and it worked much better. I was able to scrape off the
> I would ask the original supplier, but I have found out that all the
knowledgeable people are now retired and so there is no one there to answer
questions. They still have most of the parts, but those that are left are only
> The problem:
> Either I was a bit too industrious with the scraping or the grain in the wood
was just right, or the vinegar softened the wood, in any case, the small areas
between some of the pouch wells have places that are lower than the surrounding
wood. As near as I can tell, the widest being about 1/4", a few about 1/8" and
most quite a bit less. The 'deepest' is about 2/64 with some about 1/64 and the
rest less. I would say about half of the areas are 'damaged', but all it takes
> The questions:
> Will this be a problem?
> I know that the glue for the pouches is supposed to be fairly thin. Will the
hot glue fill those spaces?
> Is there something else I need to do?
> I have though about wood filler, but I and others, don't know if hot glue will
stick properly to it and make an air tight seal.
> Do you have a suggestion as to how to 'repair' those places? Or do I need to?
> Thanks for any comments for commiseration.
> Paul Masters