by Craig Brougher

Many Alternatives have been discussed by hobbyists in regard to the worth of certain hardware store glues and sealants used in antique player pianos. This is a worthy topic because of the permanent nature of many glues and sealers, as well as the performance factor of the mechanism. However in this same article is a caveat regarding some of the new glue formulations and a better sealer than the original ones, to use.

The first rule of all player rebuilding, and the one that no person, professional or amateur can conscientiously avoid is this: Do No Harm. But when most hardware store products are used, this cardinal rule is discarded.

There are some really fine glues out there, today. Glues that fill gaps, glues that are waterproof and permanent, glues that won't set for several hours or even more, and others which dry in only minutes. There are caulking compounds that are designed for 35 years of service around bathtubs and outdoors around windows. The home can collapse into dust, and all that is left are these large rubber rectangles that once sealed the windows and the tub! There are panel adhesives and glues which foam up after they are applied, filling in all the gaps. And of course, there are the myriad of contact adhesives, both water-based and solvent-based, which are so handy for those with clumsy fingers and little experience.

Now most owners of antiques and player pianos will never know what was used in their instrument because 1. They don't really care as long as it works, and 2. They will be told "only hot hide glue and original materials" if they ask (who's gonna know?). 99% of the rebuilt players I receive here for another rebuild have been rebuilt with the wrong kind of glue and the wrong sealants have been used for their pouches. Had the original glues been utilized properly in those rebuilds, the same 99% figure would have applied in reverse-- that is, 99% of those that I take in to fix right would have been working. The problem, in a nutshell, was the glue.

I can understand why hobbyists are looking for an alternative to hot hide glue, as one instance of their discomfort. It requires a little skill to maintain the right consistency, speed of application and parts placement, it has setting up properties which include the danger of making a "cold joint" just like solder (whenever the piece is moved or bumped during its setup time), the freshness of the pot, and so forth. But on the other hand, were they to just make some initial tests first before beginning on the instrument in question then practice doing what they plan to do on that instrument, most of their ensuing problems would vanish. We both know they seldom if ever want to take the time. They usually practice their techniques on the instrument instead.

It is not possible, for instance, to make airtight pneumatics with carpenter glues, all of which require water absorption by the wood in order to begin the setting and curing process. The reason for this is that there will always be several pneumatic leaves ( if not dozens) that will curl slightly from moisture as the glue sets. And since it requires 24 hours to fully dry on a normal dry day, then either the rebuilder has 88 4 inch screw clamps totaling over 100 lbs (to assemble according to instructions on the glue bottle), or else he must take his chances that they will all remain perfectly flat while the moisture impregnates the leaves. Which way do YOU think he does it?

Another problem however is with clamping itself. You cannot use the appropriate amount of glue required to make an airtight joint with any kind of glue and not slide that part under clamping pressure. You would have to brad it down first. And of course, neither spring clamps or weights can counter wood warpage. The only solution then is to use a glue that doesn't require clamps, and which sets without voids in the glue, then dries, clamping itself as it does so. In other words, hot hide glue. Hot hide glue has a "death grip" on the parts as it sets, acting as its own clamp. In other words-- it's perfect. Why isn't it universally used? Because "quick and easy" is the only requirement of those who use anything else.

There are exceptions to these general rules. For example, 5 minute epoxy by Devcon (and no other) is an excellent product. It has about the same strength as hot hide glue and sets in 5 minutes. Of course, it has to be sanded off to remove, but that is possible. In contrast, the yellow (aliphatic) carpenter glues cannot be removed from the wood, and the white (casein) glues like Elmers are almost impossible to remove, since each penetrates the wood fibers. But while Devcon dries airtight and quickly, and can be softened with heat to remove, the heat required is too much, so I would never recommend its use in the player mechanism itself, except to repair broken parts that won't have to be disassembled. I do NOT recommend using carpenter glues for anything in the piano. It was not designed for pianos, period.

The other exception that I have no problem with is Franklin liquid hide glue. Franklin dries very slowly, and that makes it exceptional glue for things like the bottom board of pianos, and the soundboard, when it can be clamped tightly to dry. Because it gives the woodworker a lot of time to adjust and to clamp, I recommend this kind of hide glue highly for these reasons, and also that it can be disassembled with water, or heated to adjust. Never use liquid hide for mounting pneumatics, however.

Regarding pouch and leather sealants, we hear today about the wonders of RTV cured silicone rubber sealants, rubber cement, and contact cement. While these sealants can be thinned with perhaps naptha or MEK or water and made lighter, They add too much stiffness to pouch leather. Rubber cements degrade too quickly with time and when they do, they become even stiffer. Good contact cements today are no longer available to the general public, so the products you must buy are themselves too temporary and often won't even do a good job on the materials they are designed for, like laminating a counter top. Many of these hardware store miracles of chemical engineering still fail in about 5 years, even when perfectly sealed away from moisture, mold, and bacteria. I know first hand. I just had to replace all my counter tops.

RTVs are perfect sealants for everything, frankly-- and if that's all you were after, they would be the all-time best since they are the slowest to degrade with time. However, "airtight" is not the criteria for pouch leather. Flexibility is. The relationship of flexibility to tightness is about 4 or 5 to one. Here is the reason:

The only moment in pouch travel time in which more airtightness is required is at the initial impulse of the pouch to remove the valve poppet's seal on the inside valve seat. Once that seal is broken, the stored energy will propel the valve up to its outside seat. However, if your pouch is the least resistive, as it will be when sealed with catalyzed sealers or cement, the momentum is used up bending the sealant on the pouch leather. Once it stands up on stiffer leather, it is resistant to return. The result is a very sensitive but slow valve. Slower to rise and especially slower to return. It will actuate and play soft quarter notes and eighth notes, but won't repeat, mostly on feather-light sixteenth notes and triplets, and anything that a player piano is exceptional at-- until you raise the vacuum. That you can certainly do. The problem then becomes dynamics. The held notes become too loud in relation to the ones that must repeat quickly.

Another problem with rubber pouch sealants is that most of the time they are applied after the pouch is glued down. This forces the typical application thickness to be much thicker around the rim of the pouch where it naturally scrapes off most of the sealant applied-- around its rim. That's the place you don't want it to go. And if you already have a lifter disk glued on, it's the main place you can put the sealant anyway. Sealing pouch leather with rubber cement in the skin first before it is ever cut for pouches is the correct way it is done. That still doesn't solve the main problem with rubber cement.

Rubber cement has, for years, been the sealant of choice for pouches. However, most rubber cements, like the kind found in office supply stores, have a very limited lifespan. For example, if you used rubber cements to glue together your kindergarten projects and you go back to your shoe box today and look at your handiwork, is it still glued together? Nope. Matter of fact, you probably can't even find where the glue used to be. That's because it turned to powder about 5 years after it was stuck together. Bad theory, bad practice. And of course, when rubber cement is applied with the finger to individual pouches in a reproducing player piano, it can be a disaster. The cement stiffens the pouches and gets stiffer after about 5-10 years. So if you own a player piano that doesn't play as well as it used to play, this is a very good bet. Not only does this product lose its tightness, but it also gets stiffer with age.

Original pouch leather was cured differently than we cure it today. It came from registered herds of sheep grown for that single product and slaughtered at 2 years old. The animals didn't require much water, and didn't get much, so that the leather would be tight. Then the skins were stretched and staked during the tanning process to make them airtight, and vegetable tanned to make them soft and supple. The result was a leather that was incredibly thin and tight without any sealant at all. Much of it is still that way. If the factory used a sealant on the leather, it was usually derivatives of glucose and proteins which could be spread very thinly into the leather before punching it out. It could not form a coating over the leather and still be suitable.

This is because any coating on leather stiffens it. It makes a trussed laminate with the leather if it is allowed to remain on top. So the only way any sealant can be properly used on pouch leather is if that sealant can be forced only into the pores on the smooth side and then wiped off clean.

Ampico felt that they could do this with rubber cement, which they were able to do. But even the best rubber cements were still hygroscopic and embrittled with time. Ampico primary pouches all must be replaced without question, and it's best to replace them all! Original pouches retained in the Ampico has become its Achillies heel, and 90% of all playing Ampicos are still judged with the original pouches intact, sealed over with a fresh coat of rubber cement. No wonder they are known to be a "salon instrument" playing background music at best. What a waste.

The last comment I will make about sealing pouches is the comment so many hobbyists themselves make regarding flexibility. Their evaluation regarding flexibility is without basis because they don't have the requisite experience to judge. How many times I have heard, "My Ampico primary pouches were still just like new, so I didn't replace them," is as common as "I have found that I can thin my silicone sealant with naptha and get a perfectly tight pouch with no change in lightness or flexibility, and they work just perfectly. Why, I can operate those pouches on 2" of vacuum with a 20 foot length of thin wall 5/32" tubing, flattened with my foot on the floor, through a #70 hole in a brass bleed."

All I can say to this is, "I test everything I have ever settled on doing, and I have never been able to get those claimed results. So if you are happy, I'm happy." I have tried to tell some people who wanted to know better, and don't think I have succeeded in all cases. I don't use any of those things and never will. That doesn't mean I haven't tried to use them and test the results. I have tried them all and spent collectively, weeks over the years to see if I could get better results. Instead today I use 111 Pure Silicone Grease by Dow Corning, thinned with a small supply of trichloroethane which I have kept. I know how to use it, how to make attachments to the same pouches when necessary, and how to optimize their performance because I test the valves themselves under extreme conditions not required by the piano. The bottom line of this exercise, I think, is this:

regardless how an experienced rebuilder may try to prevent these instruments from falling into the hands of someone who will ruin them by not listening, it is still happening every day and will not stop. That makes the good ones just that much more rare and valuable, but their true value is their musical ability. A grand reproducer in the 20's cost as much as a 3 bedroom house for cash! People then had better musical sense on the whole than our generation does, today. So to imagine them blowing their wad on a player that plays like so many rebuilt ones do today is unimaginable.

In just a few more years, these instruments are going to be 100 years old! The people who used to buy them and play them originally are going to be dead and gone. All first-hand remembrance of them is going to cease, and they are going to be the exclusive properties of future generations, in whatever state they happen to be. The techniques in restoring them are also going to die out, as more nonsense by hobbyists is written, not questioned, and published in its place, burying the correct procedures and materials under tons of baloney. This is not to discredit good ideas, as long as the correct principles and all details are carefully crafted and adhered to. Test first.

It would be good therefore to listen and learn from the professionals who are proven today, because 10 years from now, things will be totally different. Glues, materials, leather, gaskets, all will gradually fade and change. That is why the principles are the only things that last. Get the principles down and learn to apply them to everything.

Craig Brougher

Home Manuals Supplies Search Consult Contact Testing Service

This page was last revised on March 17, 2019

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