This article seeks to establish a few basic principles which apply for doing all player valves. Since we are using Ampico block valves for their convenience, and since some people might get kinda critical and say "That's just for Ampico, but my valves are different," I will give them the benefit of the doubt and then invite them to write and tell me how the principles shown here for pouching valves are any different for their brand of valve, despite the poppet or the configuration.

That said however, some valves including horizontal valves are made with a metal stems and guides. While their stem travel by design is more mechanically precise, they require a consistent poppet flexibility on those stems for tight seating, so the milliseconds required to fully seat and unseat is at least as long or even greater than for a vertical poppet because the support for the poppet must compress. If, in making the valve poppet flexible also makes it less airtight, then the rebuilder has another problem which he made for himself.

When making measurements, especially of actuation sensitivity and speed, if you cannot measure any appreciable differences when making basic changes, then you are either not measuring accurately enough or the differences are not critical to the device. Since operational speeds are very difficult and expensive to measure accurately and not worth the expense of doing it using a scope and actuation measuring devices, and since few rebuilders have those things anyway, I am going to use a more relative approach to make comparisons, which will achieve the same result empirically. All we need is a basis of comparison and exactly identical valves. How do we get identical valves then, you ask? Wait just a minute, and you'll find out. Just remember, we can be diabolical, too!

The difference in actuation speed (up travel time) of a valve is less important since the typical inside valve (secondary valve) is about 4 times faster to actuate than to return (down travel time), so its repetition speed hinges not on speed of actuation as many assume, but on reseating time. Therefore, the larger poppet might, theoretically speaking, be faster overall as long as the additional pouch resistance doesn't exceed 50%. This tells me that Ampico had a good knowledge of this variable since it is found in the evolution of the device. It costs a company a lot of money to make a fundamental change like poppet design and its inside valve seat, for no other reason than a whim.

The larger the pouch, the slower the valve. But when you speak of valve speed (repetition speed) you are not talking about taxing any note valve that I'm aware of. A good valve can repeat many times faster than any piano note I'm familiar with. So when you have a repetition capability that is several times greater than the speed that any musician can repeat a piano note, or a banjo for that matter, then response time is never a limiting factor. But we run into problems incurred with things like grand drawers, where the distance between the tracker bar and the valve stretches the limit of pneumatic sensitivity at very low pressure. Those tubes can measure almost 6 ft. in length.

The Ampico therefore would be the perfect system to test valve sensitivity and repetition with because there can be almost six feet of small tubing in some cases between the tracker bar and the valve. No other player system except player drawer grands whose stacks are behind their drawer compete with those same drawbacks. The nickel pianos and standard uprights didn't have this problem because they were not required to play reliably at the extremely low vacuum levels of a reproducing piano, nor did they have an extreme layout configuration to overcome. They were designed for musically uncritical pop-commercial enjoyment.

That said, Duo-Art also sealed their pouches but they used either a gelatin or nitrocellulose. Since they didn't use drawers in most of their instruments (until the late 30's), pouch sealing wasn't as necessary in a Duo-Art, but seaweed gelatin was more likely their sealant of choice for valves. This gelatin was also used by the case finishing departments in many companies, could be dissolved in alcohol, and was readily available on the market. Victor Talking Machine Co. used it to seal their case wood before finishing and it's possible that piano companies did it the same way, although lacquer (nitrocellulose) was used for accordions on the Duo-Art expression boxes. Regardless, all reproducing pianos had sealed pouches and leather. You will find out why this was a necessity, not an "option."

Pouch leather of the time was tanned from registered herds of specially grown Scottish Highland sheep, raised for just that purpose. When the Ampico B was designed, it was designed around pouch leather that measured between .005 and .007" thick. It is almost impossible today to buy leather that thin, without tiny holes in it. So today we must select sections out of several skins which represent their thinnest and most supple without flaws, and punch out only that portion. A factory couldn't afford to do that, today. Uniformly thin leather was necessary to quickly inspect the skins mark, and trim bad places out before sealing it. They would then talc the leather and punch it out.

If pouch leather is supple and tight in relation to its bleed size, there may be no reason to use sealer, when rebuilding regular players and coin pianos, since air-tightness is relative to the ideal bleed. But when it comes to reproducers, and particularly those with grand drawers, there is just no way around using a sealer on valve pouches. It must be done, as will be demonstrated shortly.

Any leather sealer must do two things, today. It must be able to seal pouch leather from leakage, and it must preserve the leather and protect it from deterioration. Bacteria and mold both attack leather, so whatever is used must be totally inert if possible. Animal and mineral oils are not leather preservatives, regardless what it says on the can, and stuff like neatsfoot oil (which today is adulterated) will destroy leather in short order, nor does it make it airtight, except temporarily. Oil both evaporates and spreads out. Oil doesn't like microscopic holes to fill. It prefers more support, so while it was filling the pores right after you applied it, it quickly moves into the leather fiber itself where the leather is the thickest. Don't waste another piano testing this out. It's already been done. Oiling boots to make them waterproof is a good idea because it increases surface tension, which repels water and keeps them dry, not because it makes them airtight. If boots became airtight, nobody would use that stuff because their feet would sweat. So just keep these basics in mind.

Dow 111 Silicone is used in deep space where the air pressure is zero. Were vapor pressure losses a problem with silicone like ordinary oil and grease it would never work but the fact is, silicone is not really a grease. It just has lubricity like grease. Look it up: https://en.wikipedia.org/wiki/Silicone_grease. It's a polysiloxane whose thickener is silica. That would make it a kissin' cousin to sand. No self-respecting bacterium or mold is ever going to touch it, and it's never going away. So when you thin with lacquer thinner (see NOTE), you not only kill the bacteria the leather came with, but you protect it somewhat from further deterioration, probably better than anything else you could ever use.

When it comes to thinning the silicone grease, some might ask "how thin?" But this is a matter I will leave up to you because I do it by decades of experience only. I then talc the pouches, and I don't need to seal the leather in the skin first, which allows me to use hot hide glue to install the pouch, plus add a lifter disk as required.

In this picture we begin with unsealed pouches. The white leather seems to be the tightest grain, but testing shows it to be very porous, even though there were no pinholes anywhere in the skin, and the texture was the smoothest among both samples. The finished side was actually glossy.

Remember too that the white leather was naturally stiffer than the tan. Usually, stiffer leather is expected to be more airtight, but this didn't seem to be the case. I suspect the white leather was rolled under heavy pressure to compress and stretch it. However that's just guessing. I don't know how it's made. I can say for sure their processing did not make it more airtight.

To eliminate any possibility of valve or poppet differences which would skew our results, we've designed our test to be performed equally with interchangeable blocks for the pouch boards. The boards are banded tightly to the block and then tested for sensitivity at a fixed vacuum level.

We completely eliminated any possibility for variance between valve blocks and poppets by operating both valve blocks in turn at exactly the same regulated pressure from a rotary positive displacement player pump and regulator with each pouch block. Since there was no differences between the valves that we could measure, this factor was eliminated but it was the only way to eliminate any doubts as to the chances of unknown variables between valve poppets spoiling the results. So when you see the results, know that each one included the switching of valve blocks and retesting to possibly find any differences.

The vacuum source is a rebuilt Duo-Art pump, by the way. Its regulator was adjusted to a variance between 3" H2O and 40" H2O for this test. This is checked by a Magnahelic vacuum/pressure gauge.

The picture on the left shows the test pneumatic finally pulling closed with a supply vacuum at 35" for an unsealed white leather pouch trying to operate with 10.5 ft. or tracker bar tubing. That is extremely high.

As can be seen in this side-by-side comparison, the differences in leather suppleness did not seem to come into play as anticipated. As it turned out a surprise to me, leather tightness was the primary variable and when Dow Corning 111 Silicone Grease was used to seal both pouches, these valves performed their sensitivity tests equally well.

Notice also that while testing one pouch board with its valve block, the other pouch board is shown waiting its turn on the vacuum gauge stand. It should also be mentioned that the average tracker bar tubing distance for uprights and the Duo-Art is less than 3 ft. So in order to test the relatively insensitive unsealed white pouch leather with the typical tubing "load" of a common player piano, I replaced the white pouch under each of the valve blocks in turn and rechecked its sensitivity. It easily passed the test at 5.5" H2O vacuum, worst case. This showed me that for most applications, but not reproducers, one could use unsealed leather, including the worst that I used for this test, and never know any better.

It also proves that even the easy-going Duo-Art might not quite perform at its zero intensity reliably if 5" was the threshold sensitivity of the white leather. The tan (brown) leather however would still be just fine. This proves that leather doesn't have to show pinholes before it loses sensitivity, as both of these samples were reasonably light-tight, or one could call it dense translucent since all pouch leather will transmit some light.

It isn't unusual therefore that many rebuilders believe that to seal leather is not only a waste of time, but detrimental to performance, and they are right in special cases. It requires a questioning and experimenting attitude to learn differently. If a rebuilder has only restored 88-note players and coin pianos, then he might not ever appreciate the necessity for a good pouch sealant.

Some rebuilders including myself have at times tried zephyr skin pouches and discovered that it is also very sensitive. I do not know if it is still available, but do remember that locally available gut pouch material would delaminate and was less than high quality, so for certain applications, I bought it from Germany. The one problem with all gut pouches is its food value for insects. If you can keep bugs out it should work very well except in instances where friction or direct contact with the valve is encountered. In those cases, zephyr skin wears out quickly, as I unhappily learned once. I no longer recommend it for anything in player pianos.

Another thing this experiment taught me was that leather suppleness is not quite as important as leather tightness and so I stand corrected on that score, too. I learn right along with everybody else as I perform these tests, so we all (hopefully) benefit.

There is also the second test of pouches and that would be repetition speed. Because a valve is 4 times slower to return than to actuate, repetition speed measures both together, and since repetition is 4 times more dependent on valve return quickness, it is inversely proportional to pouch sealing-just the opposite of sensitivity. By increasing pouch tightness you slow down the return and since it's the return speed that controls repetition speed, valve repetition is the inverse to valve sensitivity!

The way this problem is solved then is by trade-off. Conveniently, the Ampico B valve is equally at home with both tests because its ball bleed check valve (if new) is closed to actuate the poppet and opens to drop it. It is however the only valve ever made that way, so it excels at both.

The rest all tend to lay somewhere in-between so learning how to seal pouches for both optimum sensitivity AND repetition requires an intimate knowledge of valve differences, in case you are not dealing with primaries. That means a "perfectly sealed pouch" is NOT the perfect way to do it! So when you read that someone has a perfect sealant and their pouches are cartridge tight, that may or may not be optimum, depending on several other things including bleed sizes, pouch sizes, valve poppet design and size relative to the pouch diameter, and last but not least, the way the roll is cut.

For instance, if a roll has rather ragged-looking note holes or smaller note holes-narrower than the tracker bar holes they glide over-then if the pouch has too much cipher, its valve can actually play the note bridging as the roll travels over the hole. It sounds like a machine gun. Does that mean your valves are extra good? Not at all! All valves should be able to play many times faster than a note can repeat. It's just that note bridging is cut into the roll to strengthen the overall note sheet, while still sustaining a held note. But if a reproducing roll is cut with holes which are too small and the valves are pouched with leather which leaks too much, then the pouch drops the valve as the bridging drops its threshold and then immediately raises it again as the next perforation allows a little more air under that pouch to raise the threshold. So it's a threshold problem caused by ciphering pouches, and always on reproducing pianos which play at low vacuum pressures. Even with poorly cut rolls, this effect is almost never seen in foot-pumped players or coin pianos.

Both white and tan pouches performed on the repetition tester, too. But the white pouch was very sluggish and repetition was 17 cycles in 10 seconds at 5.5" H2O. That's not very good. The tan pouch performed much better at 32 cycles in 10 seconds. The reference model B valve in comparison made 36 or 38 cycles at this pressure (too fast to count to be sure), but this is mainly a go-no-go check.

What I then learned was that pouch stiffness apparently doesn't enter into the equation of sensitivity too much, but does have an effect on valve repetition speed. Granted, this is a very difficult test for any valve to perform at 5.5" H2O, partly because of the cc. displacement of the repetition pneumatic. I wouldn't think that it's too relevant in an actual player piano, but unless we discover a difference when changing variables (valves), then we aren't testing well enough.

In order to tax these valves to their limit, as well as answer doubts and questions, it's necessary to go to this extreme because we learn what actually works, what doesn't work, and why. It then all makes very good sense, and can be used perhaps as a basic principle of pneumatic player valve operation. These tests can also be repeated and duplicated by anyone so motivated. This equipment has been used in my shop almost 3 decades now to test valve operation and to experiment with.