Player enthusiasts of riper years here in the UK may recall sitting,

talking long into the night, at the British Piano Museum in the 1970s

with the two Palmer brothers, whose careers were spent at the Aeolian

and successor APPA factories at Hayes.



The Palmers were unequivocally clear: while some player manufacturers

and repairers used albumen (egg white), Aeolian used longer-lasting

thin rubber "cement" on its pouches (and leather-covered Duo-Art

accordions).  And indeed here we still often come across unrestored

Aeolian instruments where evidence of the talced rubber coating can be

easily detected.



In a player piano action each pouch must produce sufficient force to

accelerate the mass of its valve fast enough for perfect repetition and

to seal fully even at the tiny suction differential (about 3 inches

water gage) of softest playing.  And, so that notes occur at the correct

relative moments, valve transit times and thus bleed rates must be

predictable and consistent.  The only way to ensure this is for every

pouch to be effectively airtight.  For various reasons very thin strong

leather has been the most usual material of choice for pouches for a

century and more, but untreated it is inherently and inconsistently

porous, and therefore must be sealed.



For reproducing pianos to reproduce correctly, especially cross-valve

Duo-Arts, it is vital to achieve pouches which are airtight but

immensely supple and sensitive.  I have yet to hear any reproducer

rebuilt without sealed pouches which works properly.



Rubber cement, such as Aeolian used, is natural (tree) latex dissolved

in naphthalene (benzene).  The solvent wicks the latex polymers into

the leather sufficiently to make an inseparable coating and flashes off

quickly without evaporating any of the oils introduced after tanning to

keep it supple.  At the correct strength, a light application of the

solution will render the leather airtight without materially stiffening

it, since natural latex (polyisoprene) is still one of the softest,

most elastic substances known.



For those who wish to use rubber cement, the traditional bicycle

puncture repair liquid adhesive, such as Weldtite, is just right, and

despite health and safety attacks is fortunately still available in

the UK.  Beware the newer styrene-based substitutes which dry stiffer.

Water-based latex adhesives such as Copydex are not thin enough, do

not wick into leather sufficiently and dry somewhat stiffer unless

modified.



Though it lasts a surprisingly long time in the dark, latex, being a

natural unvulcanized polymer, eventually perishes and becomes porous.

Long-lasting self-vulcanizing synthetic Neoprene and Hypalon solutions

are available, but generally cure too stiff at about 60 Shore A

hardness.  Virtually imperishable RTV silicone (polydimethylsioxane)

adhesive/sealants which cure to a very soft and elastic 20 Shore A

work well, but the standard pastes are not as easy to apply

consistently as the liquid versions and may render some pouches too

stiff.  Attaching card lifter discs to pouches treated with RTV

silicone requires judicious use of the same adhesive.



Collodion, nitrocellulose in ether and alcohol, will wick into leather

and make it airtight.  But even the flexible acetate formulation is not

elastic, dries far too stiff and soon cracks along stress lines when

flexed repeatedly.



Non-drying silicone compounds work well, but some greases make pouches

too stiff, and light silicone oils gradually disperse or evaporate.

Silicone compounds are inert and do not weaken or rot leather.  It is

all but impossible to attach anything reliably to pouches treated with

these compounds.



Traditional neatsfoot oils soften leather and make it more supple but

like the similar oils applied after tanning essentially do not make

it airtight.  Formulations are worryingly perverse.  Some dry out and

some eventually rot leather, and those that contain waxes eventually

stiffen, especially at low temperatures.  Indeed the significant

problem with most pouch sealants is that they become stiffer at lower

temperatures and impair soft repetition.



Some 30 years ago after much experiment, I discovered a far superior

compound to any other sealant: Hydrophane Leather Dressing, made in the

UK, which renders pouches effectively completely airtight yet totally

supple and sensitive.  Importantly, it does not stiffen even at low

temperatures, and is effective for at least 25 years plus, after which

it can be re-applied.



This liquid does not rot or weaken leather and does not soften or

weaken any glues.  It is easy to apply cleanly with a small artist's

brush to new or old pouches, even those previously treated without

stiffening them, and often without disassembling a stack.  I recommend

it to everyone.  Many Player Piano Group members and rebuilders around

the world can vouch how effective Hydrophane is.



  http://www.battles.co.uk/products/001/equine/010/hydrophane/120/leather-care/5449/hydrophane-leather-dressing/ 



It's wise, by the way, to dust all pouches and sealed leather surfaces

with real talc -- not French chalk -- to prevent any sticking.



Here's an exemplary 1926 Steinway O Duo-Art, all of whose pouches have

been Hydrophaned: http://www.youtube.com/watch?v=0VsnBFELg-Y 



Patrick Handscombe

Wivenhoe, Essex, UK