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MMD > Archives > August 1996 > 1996.08.01 > 08Prev  Next

Gluing Ampico Valve Blocks
By Craig Brougher

Terry Smythe asks how to glue Ampico Valve blocks and pouches with hot hide glue. If they are "sliding around on you" and making a mess out of your pouch, then I'd suggest that your glue is WAY TOO THICK. For pouches, use a very thin mixture.

Also, when you're not used to hot gluing, you should size your pouch boards before gluing them up to the valve block body. Don't use heavy, thick glue-- just moderate. Consistency description is a problem here. If I say syrup, somebody thinks of karo, some of maple, and some of old blackstrap molasses that have sat around for fifteen years. But if you can discern the difference, then adjust to "real maple syrup." Also the quality of glue differs. The percentage of heavy proteins in the different glues allow you to use thinner mixtures than with cheaper glue. And if you forget to stir occassionally, in any pot, your best glue gradually goes to the bottom and you are skimming off the light gelatins, which are still ok for pouches, but not for wood joints, in my opinion.

Pouch setters can be made best and cheapest from rubber corks. See my book, "Orchestrion Builder's Manual" chapter on Pipe Chests to see how that is done (pictures there, too). The correctly made pouch setter is concave, not convex, and rubber, not metal (which will not conform and will double-cross you, thinking it's down tight when it's not). I also tell you how to make one. 15-20 minutes later, you will have a perfect pouch setter.

Another problem is when your pouches are made from too thick a grade of leather, and you have sanded the valve blocks' joint edge away so that there is no longer a depression for the leather to sit in. When you don't have any clearance anymore, the pouch board is just skating around on a tiny ring of leather. If that's the case, go ahead and glue anyway (This time, use heavy glue), but after they're finished, you'll have to go back through them and add more glue. don't try to do it all at the same time.

When I do valve blocks, I use a box of the very smallest rubber bands I can buy. each block gets two or three at a time, around the top and under the pouch board, then before I let it go, I get the block flat on its face, sitting on glass. They dry that way, and are almost always perfect, without any need to do any more. If it is an Ampico B valve block, I first clear out the ball bleed hole with a pipe stem cleaner before I snap the bands. The glue has to be thin enough not to be setting up on me while I'm doing this.

Heavy glue sets up quickly. Thin glue gives you more time. It's almost impossible to get too thin a glue for pouches, but I suppose somebody will do that and prove me wrong. Maple syrup consistency is about right for good glue with valve blocks. The better the glue, the thinner you can get it and still have all the strength with low shrinkage. Color of crystals are no indication of good glue. The best glues however are about the color of maple syrup as soon as they are made. Technical gelatins are relatively weak, but usually strong enough for our purposes.

The worst thing somebody can do is to use carpenter glues (yellow glues) or epoxies on Ampico valve blocks. Not only can they not get them back apart, but the joint will "creep" and in a year or less, the valve block will be useless and usually unfixable. All your bottled and tubed glues are plastics, and plastics deform and stretch over time under a constant tension. That is why they will never hold loose chair rungs for long, or fix furniture joinery unless it's a lap joint and screwed together. A good joint is, by itself tight, and the glue prevents it from coming apart. There is only one kind of glue that both makes a sloppy joint tight and also prevents it from coming apart, and that's a glue that is not plastic and will not deform over time, and which makes both a mechanical and a chemical joint with the wood. That's hot hide glue (a good grade of, that is). A wood joint cannot be flexible and hold for very long (contrary to popular opinion). Therefore, a wood glue should not be flexible, either. That's why they have never improved on animal hide glue.

Craig B.

(Message sent Thu 1 Aug 1996, 15:59:59 GMT, from time zone GMT.)

Key Words in Subject:  Ampico, Blocks, Gluing, Valve

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