Engineering in wood
A piano consists of a strong wooden cabinet. Inside is fitted a thin wooden soundboard.
Wooden bridges are glued to this soundboard. Stretched across the bridges are measured lengths of steel string. The strings at one end are fixed to tuning pins mounted in a block of high grade laminated wood so they can be tuned.
Wood, you may have gathered, is the predominant material in a piano – but it doesn’t stop with the structure; there is the mechanism, the ‘action’ and also the keyboard. All engineered somewhat remarkably out of wood.
The Action
The action is manufactured from a variety of hardwoods. Hundreds of wooden parts fit together and with the assistance of springs and weights, these wooden parts combine to create an efficient escapement movement, thus giving a pianist very precise control over the velocity and dynamics of each note played. Felt hammers strike the strings, but there are also many other felt pads, pieces of baize, woven strips of cloth and leather, all carefully placed to act as cushions or buffers, or bushings. Their principal purpose, to keep the action working smoothly and silently, thus allowing the vibrating strings to sing out clearly and cleanly; without any unwanted clicks, squeaks and thumps to detract.
The soundboard, a very thin board of sitka spruce, amplifies the sound and contributes greatly to the tone. The musical vibrations must travel unimpeded through the fibres of the board. Only fine quality, knot-free wood is used. It has to be a perfect resonator.
The bridges affixed to the soundboard are of hardwood, often beech. They need to withstand considerable downward pressure from the strings. This pressure is known as the ‘downbearing.’
The soundboard is crowned – it bows outward slightly in the centre to help it resist this pressure and ribs are glued to the back of it for added stability. In the first picture above you can see the strong wooden back posts of an upright piano. The golden coloured wood is the soundboard with its diagonal ribs. Often on an upright piano this part of the instrument is hidden by a backing cloth and on a grand piano the rib structure can only be seen if you crawl underneath.
Strings, Pins and Things
The downbearing exists to ensure good contact between strings and board and consequently good transference of the sound. The main force exerted by the strings on the structure of the piano however, is not the downbearing, but the combined tension from top to bottom of the instrument (front to back on a grand piano). Over 200 strings at high tension exert nearly 20 tonnes on the structure. This is where the strength of wooden posts alone is not enough. A heavy cast iron frame is therefore added. This item unfortunately makes a piano a difficult musical instrument to move around – which is why it is important to find the ideal spot for it before it arrives in your home.
The tuning pin plank, wrestplank or pinblock is a thick piece of laminated wood fitted at the top of an upright piano or near the front of a grand piano. It is drilled with over 200 holes to take the tuning pins, to which are attached the strings. Each pin must be tight enough in its hole to hold the string at the desired pitch, but not so tight that the pin will not turn smoothly to allow fine tuning.
Humidity Care
Wood is very responsive to humidity levels. If conditions are damp, then it swells. If dry, it shrinks. Even though the wood used in a piano is of the best grade and is carefully seasoned, it still behaves in this way. Great care needs to be taken to ensure that a piano is not exposed to extremes, or extreme fluctuations in humidity.
When humidity is high, keys can stick, actions can become sluggish, the soundboard swells and bows outward slightly at the centre, pushing the bridges out, thus increasing the tension on the strings, sending the musical pitch sharp. If conditions are very humid then strings and other metal components can rust or corrode. Conversely, if humidity is too low then the soundboard shrinks and flattens out and the musical pitch of the strings drops.
The board is actually made of several thin strips of board glued together at the edges. If it shrinks too much then these joins can pull apart and cracks can appear. A cracked soundboard does not resonate as it should; the piano suffers loss of tone and tuning instability due to erratic movement of the separated boards. It may even produce unwanted buzzes and vibrations.
The above picture shows a crack which has been repaired. Such repairs can only be effected when the strings are removed from the piano and the iron frame taken out – major work!
Excessive dryness can also cause splits in the hardwood connecting bridges. It can also loosen the precisely positioned action parts, causing operational havoc and can even loosen the tuning pins so that the piano sounds permanently honky-tonk.
You may think that in a home, conditions would not be so extreme. To a large extent this is true. Pianos enjoy a similar environment to us – not too hot or too cold, not too humid or too dry. So a room suitable for human habitation should also be suitable for a piano (That rules out the kids’ bedrooms then)! However, care must be taken not to position a piano too close to a heat source such as a central heating radiator, or in direct sunlight, as these can quickly dry out the wood and cause severe damage as described above (not to mention the ‘fading’ effect of sunlight on the casing).
Steamy places such as kitchens or cold out-buildings or places near to a regularly opened window may not be suitable locations either, as the combined effects of high humidity, fluctuating humidity and possibly condensation could cause serious harm.
Acceptable humidity levels are between 50% – 60% relative humidity and the ideal temperature should be normal room temperature. By achieving these levels you will not succeed in preventing the piano from going out of tune, but you should save it from going out of the house into a skip!
Excessive humidity can occur on the inside of outdoor facing wall, or in other parts of old properties. That wonderful 14th century cottage in the country can be a hostile environment for a piano.
There are several devices available to control the climate around your piano.
Care of the Polished Surfaces
On the casework, it is unwise to use furniture creams, waxes or sprays. A satin finish requires only wiping with a cloth dampened with water to which a drop of vinegar has been added. Glossy polyester finishes can be dusted and marks can sometimes be removed with a chamois leather but care must be taken not to scratch the surface.
Older pianos were often French polished. This polish can sometimes be revived using a proprietary French-polish reviver. Always try it on an inconspicuous part of the piano first. Try not to keep things on top of your piano. Any vessels containing liquid, such as vases of flowers, etc. could well spill and seep inside to damage the action of the
instrument.
Tuning
Regular tuning ensures not only that the piano is kept in tune and at the correct pitch but also in good working order. During a tuning, small adjustments can be made eg. to ensure parts stay aligned – thus avoiding premature wear. If the action requires more work, the piano tuner can advise.
Picture shows worn hammers where the felt on the hammer nose is wearing close to the wooden centre core.
If the time gap between tunings is too great then the condition of the internal workings can be more difficult to monitor. A more out-of-tune piano can take more time to put back in tune, leaving less time for other adjustments. Economising on tuning may not be a good saving in the long run.
Key Care
A piano’s keys need to be treated with respect. The front lip of the white notes is particularly vulnerable to damage. Generally though, the keys need little attention other than periodic dusting.
The piano’s keys can however get grimy over time. The best way to clean the keys is with a finger wrapped in cotton cloth and moistened with a solution of water and washing-up liquid. The cloth should not be saturated – only dampened. It is imperative that water is not allowed to run on the keys or spill down the sides as the key coverings could become loosened.
It is difficult to remove yellowing, particularly if the coverings are made of plastic or celluloid. Yellowing of ivory can sometimes be prevented by leaving the fall (The lid that covers the keys) open as exposure to sunlight helps keep them white.
Your Piano
A piano is not just a musical instrument it is also a piece of furniture. Unlike many other instruments it cannot be shut away in a cupboard when not in use – it has to live with you and you have to live with it. It responds to the care it receives by giving years of lasting pleasure. This may be the reason why many people get attached to their pianos which become loved and cherished and passed down through generations.
© 2021 M S Butterworth. All rights reserved
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