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MMD > Archives > April 1996 > 1996.04.09 > 04Prev  Next

Re: Sealing Pouches
By Craig Brougher

To answer a chap named "BILLCHAP" at who said:

> Since we are on the subject I thought I'd mention my experience
> with the Dow-Corning leather preservative that was put out in
> the 1980's.  It was supposed to be the living end in leather
> preservative, and in fact it did a good job on the large pouches
> under the pipes in the Reproduco that runs on about 5" of wind.
>  However, it did slightly stiffen the leather, turned it a rusty
> brown color and yet it still took glue for the pipe valves.  I
> wouldn't be inclined to use it again, because rubber cement (or
> nothing) seems adequate for pipe valves in our clean and moist
> Seattle air.  Note, this is probably NOT the same product that
> Craig B is using.

    He is probably right. Although I have never seen a product, no
matter how perfect it is, that can't be used to absolutely RUIN
anything, when one doesn't understand the technique!

    I might also add that not only will this grease not turn pouches
any color at all, it will not stiffen them either, when used properly.
Of course, that requires something other than a paint roller and a
thickness a bit less than your shaving cream in the morning. I received
a letter from someone personally who apparently had done research
regarding the Dow Silicone oils in the mid-sixties. He remarked about
the wide variety of viscosities available. This product is used in the
food industry to lubricate heavy machinery used in food processing, I

    The sealing of old pouch leather is seldom a very wise thing to do,
although this is what most rebuilders seem to do anyway. The fact that
large pipe organ pouches were made stiff indicate to me that the
leather was partly dry-rotted.  I've tried it, just to see what
happens, and have proved it over and over again. Dry-rotted leather is
slightly thicker than it used to be, and very porous just under the
surface. So when you soak it up with an oil or a grease, it gets very
stiff. The proof that it was dry-rotted! Strong, new, tight leather
pouches do not get stiff. Billchap also writes:

>   As for mink oil, it was advertised as keeping leather supple
> and soft, but the organs playing on lighter pressure (like 2.5
> inches) pressure soon refused to play.  The pouches were so
> stiffened by mink oil that they wouldn't open on low pressure.
>   --Add'l note, I took apart the 70 year old Duo-Art, and the
> leathers were still good.  Luckily, I found no trace of
> rubber-dust, so simply re-sealed them with rubber cement.
> Worked fine.  I did tear one apart to see how much dust was
> under it, and to see if the leather was fragile.  Plenty of
> dust, but very strong leather.

    Mink oil is very absorbent and the fact that it stiffened the old
pouches so badly that they wouldn't even operate is in indication
to everybody that these pouches should have been replaced, not just
sealed!  Because Mink oil should not stiffen good leather very much,
especially large pipe organ pouches. As long as you are taking the time
to tear this stuff apart anyway, why just "treat" it? Why buy all that
time and effort, and STILL NEED NEW POUCHES? And once you have treated
one, wouldn't you check it out first to see if you had helped it or
hurt it? It's hard to tell why or under what circumstances this was
done, of course, so I am just idealizing within a shop without time or
material constraints. Don't think I am criticizing you, Bill. I am
addressing my comments to so many rebuilds that I have had to undo over
the years. It makes me a little peeved to see so many people cheat
themselves out of a great job just in order to save a few hours.

    The Duo-Art comment was especially good. Here, old pouches were
sealed with rubber cement, and Bill says he would use rubber cement
anyway, regardless of its time-tested properties. Here is a letter
quoted from another one of our group who replied personally: "I
couldn't agree with you more (about Silicone grease)., but I can
remember experimenting with Dow Corning Silicone oils, recommended for
the purpose by D-C in the mid-sixties. A wide variety of viscosities
available, and stable. I also applied them with a solvent to act as a
vehicle to get total penetration into the leather."... " I also think
rubber cement would be a mistake. It oxidizes quickly and turns to
powder, just as you said. Thanks and best wishes, ____"

If anybody knows what Duo-Art used as a sealer for their pouches, I
hope they will share it with the group, because it was superior to
everything else.  Whatever it was has prevented most of the dry rot
found in other players over the years.

Terry Smythe asked where to find 111 Dow Corning Silicone Grease. Well,
I buy it in the cartridge at IBT (Industrial Bearing and Transmission).
I keep a quart jar of it thinned and ready for new pouches. I can tell
about how thick to make it by its viscosity on the brush, but as I use
it, the thinner evaporates, so I keep it thinned a little as I go. It
isn't critical, and it certainly doesn't stiffen pouch leather. The
rubber cement trick definitely stiffens pouches, though. If you don't
believe it, try this little test:

   1. Rebuilding some Ampico or other block valves, set the valve in one
      of the blocks before gluing on the pouch board.

   2. Seal one pouch with rubber cement, and one with thinned Silicone
      grease. Put both of them on a bubble test jar and adjust the jar
      so you get the same number of bubbles/min.

   3. Make a pouch leather gasket , clamp tight, and test each pouch
      for sensitivity, as described below.

	a. Supply a bleed if necessary and using a very long pouch
	   tube, say 6-7 feet, drop a regulated vacuum supply to about
	   4.5 to 5 in.H2O.

        b. Test until the grease-sealed pouch will just barely make it
           up on occasion.

	c. Replace that pouch board with the rubber cement -sealed
	   pouch board and run the same test again. If it even moves
	   the valve at all, then you have achieved something I could
	   never get it to do.


(Message sent Tue 9 Apr 1996, 14:48:36 GMT, from time zone GMT.)

Key Words in Subject:  Pouches, Sealing

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