Pianos: Punching Above Our Weight

Underneath every piano key there are paper and cardboard punchings (or washers) stacked under a cloth punching. Usually these days the punchings are commercially produced, but in earlier or more austere times, they were produced from whatever resources were to hand.

I find the home-made paper punchings utterly beguiling. But at 80-odd years old, even if they are still looking respectable, they are due to be replaced. The role of the paper and cardboard punchings is to finely adjust key height (at the balance rail) and key depth (how far the key travels down when you play it) at the front.

I should add that no one makes their own paper or cardboard punchings any more, but it could happen, come the Armageddon.

It's not hard to imagine that paper and cardboard will degrade and change. Cloth also changes and degrades. It might plump up with increased humidity or compress with use. In older pianos such components have often disintegrated. Witness the green powder which has come from the cloth punching that I have lifted to reveal an ├╝ber-cute Deutch donut. 100-year-old paper is lucky to still be there. 

One might say that this keyboard needs levelling, to say the least. To be fair, this is not a working instrument, but rather a museum exhibit in (famed in piano circles) Hamamatsu, Japan. The series of complex lozenges that make up the black keys (and the little extra black keys) reflect a point in the history of scales and temperaments when keyboard makers grappled with the conundrum of how and where to deposit the mathematical surplus that is the result of no collection of pure interval ratios coinciding with the size of an octave. Suffice it to say that there have been myriad methods of tempering intervals to make them fit and somehow serve the musical requirements of different eras. 

We gradually moved from sweeping large piles of dirt under certain parts of the rug (then treading only fleetingly there) to wanting to have all tonal centres equally useful and harmonious, so we spread the dirt thinly and evenly under the entire rug. You'll never tread on a lump, but there's still dirt.

The Hamamatsu keyboard represents a time when instrument makers experimented with offering alternative notes within many keys. They would be the 'same' note tuned slightly differently. The F# you'd like as the third in D Major is not the same F# you'd like to be the fifth of B minor. The pursuit of universal purity was unattainable on such fixed-pitch instruments. The cumbersome requirements of playing such keyboards sealed their fate. But I digress.

At the famed Piano Olympics, where faceless pit crews toiled in the wee hours, a very new piano was subject to intense performance rigours. The regulation of the keyboard needed attention repeatedly, it continued to change so much. One session wrought as much change as a year might under more conventional use. Additionally everything in a new piano is less stable than in a piano that has been played, tuned, regulated and generally 'run in' for a year or two. 

A straight-edge that spans the width of the keyboard is supported at each end to regulate the black keys' height above the white keys. 12 to 12.5mm above the (levelled) whites is standard.

Backlighting can be a great way to expose keys that need paper punchings to be added to the balance rail pin. An approximate rule of thumb for grands is that what you might measure at the front (when determining height) you'll need about half that measurement to be changed at the balance rail (whites). For blacks it's roughly two-thirds. 

Superhero Tech carries his punchings in various ways. They might be in bags or boxes, but the predominant method is with workshop-made wooden whatsits that we lovingly call abacuses. I've never graduated beyond fishing tackle boxes myself (pictured, top of shot). At first I thought the abacuses were absurd, but I have lukewarmed to them.

The skewer method of toting is only appropriate for stiffer cardboard punchings, not thinner paper ones. I suspect the skewer method is one borne out of an improvisational in-the-moment MacGuyveriness rather than it being a standard methodical approach - in the manner that a hotel room shower cap becomes a container when all other plastic bags have been deployed.

New paper punchings (an almost skewer-worthy thin cardboard in this case).

On a Bechstein piano from 1927 we are most likely seeing the severely degraded original balance rail punchings. They are kid leather, which is sometimes used. The mess makes the Grotrian Steinweg's white balance rail cloth punchings (below) look kind of OK, however, the piano will benefit from new cloth punchings.

The Caped Regulators prepare. The front cloth punchings (green) are still in good condition and will be retained. I always love it when a man does 'women's work' or when piano doctoring gets just a bit Tonia Todman. A bit more craft work than kraftwerk. Finely woven durable cloth (not felt) will be punched to produce replacements.


We'll be needing punches, large and small. We'll need an alloy wheel with stylish tyre, and several replacement license demerit points to combat the rampant scourge of ever-changing highway roadwork speed limits. Clearly this was after the event, a shot that documented unloading the car rather than providing blogworthy narrative fodder for this little sidekick. 

Bushing cloth comes in various thicknesses and has a laminated weave. Notice the white sandwich filling. The cloth is expensive. I have it on good authority that Prince Philip himself could not make a kilt out of it. But perhaps that's because he cannot sew. My thrift compulsion makes me attempt to waste as little of the cloth as possible, but I discover that it is better to have just a bit more breathing space between each cut than what you see above.

Nonetheless, the (mercifully not sweaty) sweatshop forges ahead. Quality control dictates that any punching that looks just a little too much like a Simpsons eyeball is rejected. I was relieved that I was not the only one who had produced a few googlies by not centering the small punch.

It's a darn pretty piano.

It's currently working hard in a recording studio.

My mission to bring you vignettes of piano workshop life sees me reveal some pin block wood, with test holes and tuning pins. Pin blocks are cross-laminated planks of hardwood (usually rock maple or beech). 

Drill bits are being used as gauges to test hole sizes in a pin block. Holes that may have started out (at least theoretically) identical may differ through having been tuned more (or less) due to variations in the original pin block wood, due to inconsistent drilling or other repair work (for example, an oversized tuning pin may have been fitted to resurrect a too-worn hole). Measurements across the pin block will assist in choosing the best 'next-size-up' tuning pins.

The only other times I might be tempted to make my own punchings would be when beset by a phalanx (yes there really were several) of noisy backpack vaccinators. Annoying, but one must find a way to duck and weave to hear to tune... or wait... or ask them to go clean that other church belonging to the opposition God Squad. OK, that has never worked. Let's not confuse ecumenical with ecky-thump!