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MMD > Archives > April 1996 > 1996.04.07 > 03Prev  Next


Re: Coating Pouches
By Craig Brougher

The discussion on coating pouches peaked my curiousity and so I thought I might just add my two cents, too.

I have used a thinned-down solution of 111 Dow Corning pure Silicone Grease on new pouches. I'll tell you why in a minute. Lifter disks are put on by dipping 3/16" dia. cloth punchings into hot hide glue, centering them, and placing the lifter directly on top. That way, glue doesn't spread around under the lifter and stiffen the working portion of the pouch too much.

Carter's rubber cement has been recommended for years to do this sealing bit, I realize. Several very good rebuilders still use it faithfully. But if one would just go back through their kindergarten art their mother saved for them, they would also discover that Carter's rubber cement is hygroscopic and turns to powder in a few year's time. What you thought was glued together for all eternity has long ago disintegrated.

If you think that players are different, I would invite you to look inside of an old Ampico which used rubber cement on the pouches, and you will find some of the STIFFEST pouches in the business, as well as some of the leakiest. The reason is that after awhile, rubber cement sort-of "work hardens" and the pouches form a "donut." The very place where such a pouch works the hardest is right at the edge of the hole, and this is where the rubber cement is probably the thickest, if the pouches were sealed after they were placed.

If you want to prove this, it's simple to do. Pour a little dye stain into the rubber cement sample and using your fingers or a brush, just paint a few pouches with it as you usually do. Don't try to get the colored cement "even." Don't cheat yourself. Just see where it ends up. And you'll then notice that the edge of the hole squeeges the glue off the applicator and ends up getting the darkest.

Mink oil is just more baloney, in my estimation. First, it isn't a very good sealer because under low pressure conditions, it creates a vapor pressure and distributes itself as a fine, oily film all over everything inside the player. That means metal valve seats, especially. Now as moist air is pumped through, the oily fim being lighter than the moisture traps the moisture under it, and after a few years, you get a beautiful, green trim growing around the edges of the valve plates. Proof of mink oil, or any other oil or grease used as a sealant, if that grease is lighter than water.

Silicone grease is best, because it is heavier than water, it doesn't form a "vapor pressure" under any conditions, it is absorbed perfectly into the leather, it doesn't migrate, and it truly preserves the pouches while not causing them ever to be stiff.

I still use trichloroethane to thin it down, but lacquer thinner works just fine, too. Once you have a sealing solution, seal a few, dry them thoroughly, and test them for tightness. If they still leak a little, make your solution a bit heavier. Once you get the solution right, write it down so you can make some more. Talcum the pouches (do not use cornstarch. Bacteria can turn the starch in cornstarch into sugars that draws insects, and encouraging bacteria growth accelerates pouch disintegration). Talcum powder repels insects--even destroys them in the same manner that diatomaceous earth kills insects. And as far as mink oil goes, it too is edible and tempting to insects, mold, smut, and bacteria.

I really urge rebuilders to remember the principles and to do it right the first time.


(Message sent Sun 7 Apr 1996, 14:38:32 GMT, from time zone GMT.)

Key Words in Subject:  Coating, Pouches

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