By Craig Brougher

I've been passively reading the complete nonsense posited in the MMD (Mechanical Music Digest) this January of 2007 regarding a new and improved method of gluing pneumatics to the decks of player mechanisms. Did you know that we who use hot hide glue and original methods to restore these instruments are now considered "masochists" by a new breed of advanced and savvy rebuilders who laugh at our futile attempts to do it the original way, when there are better and more modern methods available? What am I speaking of, you ask? The magic adhesive is RTV, otherwise known as BATHTUB CAULK. Not that RTV is their only innovation. They are also using a caulk and sealer known in Britain as Unibond (polyvinyl acetate emulsion intended to stick things to gypsum board in a dry environment), or some versions of this PVA you may know as "Liquid Nails". They call it that, I guess, because it isn't a liquid, and we all know how disturbing it is when things are named what they are. Liquid Nails is a thick, space-filling, permanent caulking adhesive used in caulking guns for sticking wainscoting and paneling to walls without nails, or using fewer nails. Perhaps this new breed of player rebuilder also learned that he too might use fewer nails in his own projects. It must have been quite a temptation.

But don't take my word for it. Let me excerpt a few more qualifying comments from this fellow and others who want to follow his advice, who seem now intent to prove how little use the original glues have any longer. I think I'd call this, "Stick-to-it-iveness". Or, others might call it "rationalization". For instance, and this is precious -his philosophy why we all had better start using RTV:

"There is a possibility that hot animal glue may be banned through controls over infectious proteins. Already most traditional methods of tanning are banned because of the noxious and toxic chemicals previously used (including, up to WW2, I kid you not, dog sh*t)."

(Hmmmm. Does he refer to "traditional dog shi*t?")

"Traditional hot glues were used mainly because they were so cheap, and huge quantities were used in piano and player manufacturing rather than other adhesives such as casein or latex (which were available a century ago) or fixings such as screws, all of which were significantly more expensive."

"Hot glue is actually relatively unstable, softening with humidity and tending to crystallise and become brittle if chilled too fast, desiccated, or subjected to repeated stress.  (Hence the need for tropicalised pianos.)  Hammer heads stuck on with hot glue, for instance, are often found to be quite loose, which leads to odd sounds. Therefore few musical instrument manufacturers and professional piano rebuilders have used hot glue for some time.  Adhesive technology has advanced enormously since WW2, and there is a vast range of more reliable permanent and semi-permanent types available."

In the first place, if tanned hides were noxious and toxic, then we would all have incurable diseases millennia ago. I wonder if this fellow ever heard of…shoes and belts, for example? And regardless what is used to tan hides, those chemicals, vegetable, or animal matter has long since been rinsed from the leather, which has been softened for use. When hide glue is made, it is started by soaking tanned leather scraps in lye vats, which dissolves them, chemically (you can do it organically however, with enzymes from... well, you know). However, these skins that dissolve to make the glue come from the same leather that your shoes, coats, and auto seat covers come from.

The reason that hide glue is so cheap is because there is such a great demand for it. It has been used ever since man first decided to build his first chair. "Unstable?" I don't think so! "Softening with humidity?" Absolutely ridiculous. Hide glue is the most dimensionally and chemically stable adhesive of all time! When completely dry, as in a chair rung or box joint, no amount of humidity and no amount of years in those conditions will cause that joint to creep or loosen (PS: Dampness over a long period of time doesn't score as humidity). The only way to loosen that joint is to apply water and heat, and keep it actually wet until it comes apart. That is more difficult to do than you would think. You would have to soak the chair in water or steam it apart. Restorers of old furniture can attest to this. Hide glue is far more permanent than say, epoxy, because it will not soften under a low heat. Epoxy, on the other hand, softens long before the wood starts to scorch. A dry animal hide glue joint's breakdown temperature is 475 degrees F. That's the temperature a match ignites at.

So is it now time to bring in the clowns? Let's read some more:
(Note that "white glue" is a meaningless term.)

"Many glues are white when liquid but utterly different. PVA is polyvinyl acetate, water soluble; casein is milk protein and usually water-insoluble when set; Elmer's glue and Phenoseal are water-insoluble PVC, polyvinyl chloride and phenolic resin(!). Copydex is water-insoluble latex rubber. Some craft glues are PVA but many are starch gels not strong enough as structural adhesives."

"All the above glues, including hot glue, are organic compounds. RTV (room temperature vulcanising) silicone sealant adhesives are polymerising silicones, organic compounds of silicon. Silicones have been around since the late 1940's and are very stable. Until relatively recently they were very costly. Normal RTV's set not by solvent evaporation, but through catalysis by water vapour, whereupon they liberate a small amount of acetic acid (vinegar) vapour, so they are very tolerant of damp surfaces."

His comment that all the above glues are organic compounds is apparently intended to show that he has this scientific basis and therefore you should give his comments greater credibility. I know of no other reason, and since there are east-west differences between their characteristics, we have a choice now -we can either chose an organic adhesive, or... an organic adhesive. Thanks a lot- that was truly so helpful. Remember, rebuilders: Look for the "Organic Adhesive Label".

Nor do I care if they smell like vinegar (oh excuse me, I meant...Harrumpf..."Acetic Acid") or lacquer thinner, or caramels. There is no point, here.

The rest of this inane drivel is immaterial to the question, anyway. The real subject here is, should we or should we not use bathtub caulk and Liquid Nails, and similar space-filling adhesives to repair player mechanisms?

Let's concern ourselves with just one of many operations -the replacement of the striker pneumatics on the stack shelves. What is wrong with RTV after coats of PVA sealer on these surfaces? After all, it supposedly removes very easily, according to this author. Please follow the logic:

When pneumatic bellows are removed directly from their wood to wood joint, there is always torn wood involved, both to the shelves and the stationary leaves of the bellows. Now it doesn't matter how much sealer is soaked into torn and broken wood to "seal it" since RTV gets its holding strength against surfaces mechanically, not chemically. That means the microscopic and macroscopic terrain of the two surfaces creates the tightness of the bond. Wood pores, tear-outs, rough sanding marks, scraping lines, etc., all strengthen the bond and make it possible. To rebuild such a mechanism again would be so difficult as to be practically impossible. Don't believe the story that if you coat both surfaces with a thinned-down PVA, that removal is a breeze. It is not. And while rebuilding such a botched up instrument is practically impossible, rebuilding it again the right way with hot hide glue is completely impossible. The glue will simply bead up on such surfaces (I also speak from experiences). Why?

The bond between hot hide glue and wood, leather, cork, rubber, etc., is NOT a mechanical bond! Yes, you read that correctly. The bond which hot hide glue makes to all surfaces it attaches to is a chemical bond. That also means that the material it attaches to does not require roughness to make a good bond. It can be as slick as glass. As a matter of fact, certain grades of hot hide glue stick so tightly to glass that it spalls it when it dries and shrinks, thus creating the art business known as "glass chipping." You see, molecular bonding requires very specific kinds of molecules to make connections with, and once they are made, that connection becomes a stable chemical compound with the material it compounded with. No wonder hot hide glue is so strong! It isn't just stuck there like dried jelly on a tabletop. There's more to it. However, water dissolves the compound it makes with the other material. Well that is, unless you want to make it waterproof by adding certain metal salts. That's another use of hot hide glue. Ancient shipbuilders knew that method well. Talk about "humidity?" Now there's some real humidity. You don't want to hang on to the railing for dear life if it's going to loosen in a storm, or the tiller comes apart in your hands.

But why do you suppose hot hide glue is so out of favor in a few player rebuilding shops, today? The answer comes from this same author (above) who posted a letter calling rebuilders who did use hot hide glue, masochists. In other words, this fellow never did learn how to do it! One thing I found out was, his pneumatics were sliding around on him every time he clamped them down. Strange how that works. He needed a glue that he didn't have to clamp.

Well, the only reason a person would ever clamp pneumatics to the shelves they mount on is, 1) he doesn't know what he's doing, or 2) he wants them to be skewed all over the place, as in some abstract artistic project. You see, clamps tend to do that. Anything that doesn't exert a perfectly vertical force skids the joint slowly. Such a joint then is very weak as well and often breaks in use because hot hide glue sets by jelling. It does not set by evaporation! Very important point.

How does one then glue pneumatic bellows perfectly? Well, in most cases, if your glue is the right consistency AND you have pre-coated the shelves with a prime of thinned hide glue, now set up or dry, then you seldom need any weight at all.

Hide glue has a characteristic known as a death grip, and once beginning to jell, cannot be moved easily, again. But for those instances where the part is not self-supporting, you would use a set of lead weights or metal pieces that you've collected and laid up for just that occasion. That isn't hard. But no one who knows much at all about gluing would ever use a spring clamp on a flat joint. From subsequent discussions, I seem to think this was the primary motivation for the RTV in the first place, but I could be wrong. On second thought, who cares?

The modern alternative glues are not good because they ruin the historicity of an antique and a valuable instrument. We are just custodians of this wonderful piece of Americana and/or Mechanical Musicalia in general. Part of the charm and comfort these instruments should provide includes a certain confidence in their restoration and their rebuilder, and the assurance that they are playing on original or similar materials, put together the same way they were originally, with the exact same glue that was used 100 years earlier (and then, 5000 or more years before that). It is also confidence in its restorer who has mastered the use of these original types of materials and is capable of making them play authentically without resorting to the modern products which ultimately are not "easier," but initially requiring far less skill and understanding of many inherent pneumatics problems. Such better knowledge would have otherwise served him well when it's time to troubleshoot his own mess. I don't envy him the problems he makes for himself.

Regarding the suitability of using alternative adhesives like RTV's, PVA's, and LMNOP's for "lesser" instruments, I'd like to blow this one out of the water, right now! What is a "less significant instrument?" Answer that one, and I'll agree with the total (lack of) logic, immediately. Is a "lesser instrument" great grandma and grandpa's family heirloom which was loved by everyone when we all came to visit? Shall we glop that up, then? Well, Joe has a Haines upright Ampico but Bill owns a Knabe grand. Which one shall we glop up? But wait, Sally owns a Mason & Hamlin grand Ampico, Hmmm... nice, but that doesn't beat Maurice's Seeburg G, But now we've also got a Hupfeld in the que. So that means everything I've mentioned so far gets RTV'd, right? Let's get these out of the way quickly so we can start on...OOPS, wait just a minute, someone's now inquiring about doing their Wurlitzer Concert Pianorchestra! A "lesser instrument" depends on who's appraising it, and on what basis.

Now some may say, The straight player piano is the "lesser instrument." But the owner of that player piano doesn't think so! Besides, he intends to play his player piano every day and has thousands of rolls for it. He isn't going to turn it on for guests, once every 3 weeks or so. If we go by the monetary value as to the definition of "lesser" we are no longer rebuilders, but auctioneers. And there's that overriding fact of life that once you start RTV-ing "lesser instruments," you begin a bad habit that will express itself throughout everything else you do, from then on. You have lost your integrity. "Faithful in little, faithful in much. Unfaithful in little, unfaithful in much." Had you been a expert (in fact), you would have been praising hot hide glue to the heavens and would not rebuild without it.

Hide glue is not only a far superior product, but also the easiest, ultimately, to those who know best. The fact that amateurs who use alternative adhesives suggest them for "lesser instruments" is a global admission that it is also the less desirable way of doing it! I insist it is the very thing that should never be done to any instrument-if you ever want it repaired, sometime, and I am surprised that MMD would entertain the idea. I think it shameful. It doesn't cost any more to do it right, with original glues, all the way through, and get it guaranteed to you. If you have any doubt, have your rebuilder put it in writing that he will use only hot hide glue on the major wood to wood sealing joints throughout your player. Let's start the process right and separate the men from the boys. Let them come up to our standards, rather than dropping down to theirs.

Over the years I can say that, after having hired dozens of people to help me in the shop, the one thing that every one of them assured me of was this: They were very good at using glue. And the one maxim I took away from their initial assurances, which has served me well over the years is, "If I could only teach someone how to glue, and get really good at it, I could teach them anything else as well." Why were these people so universally BAD at what they thought they were so universally GOOD AT? It's because they thought they were talented gluers and really had little else to learn about it. Nobody finds an answer to anything unless they have a question or a doubt.

Craig Brougher




I Don't..






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