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Some of the Effects of Deep Cycling on our Pianos

What happens to your piano after the deep cycling of temperature and humidity we have been experiencing? This winter (as if I have to remind you) was exceptional in the unremitting cold which lasted 30 – 45 days longer than normal. Time will tell if this summer will match the winter in its extremity. But with one leg of the deep cycle completed, I think it is important to take a moment and consider what this winter did to our pianos.

The wood and felt in our pianos has lost much of its moisture; here is how some of the wood and felt components have reacted to these dryer conditions.

Keys

While wood may shrink as it dries, counter intuitively, the many holes found in the keys may also shrink causing key bushings and key pins to bind. Also the keys may deform and begin to rub on their neighbors. As the wood dries, the bond between your key tops and key sticks may break. It is not unusual for key tops to begin to lift, making clicking noises when played, or even just come right off. As your keys change dimensions, your piano’s action regulation can become very erratic; your keys may no longer be level and your hammer line (properly known as the blow) can become quite uneven.

Felt and Glue in Hammers & Center pin bushings

As your hammers dry out, you may find the tone quality becoming more “tinny” and thin sounding. The hammers will lose some of their resiliency. A less resilient hammer will bounce off the strings instead of “pushing” off, thereby leaving the upper partials more active, giving a tinny sound. It is also not unusual for the glue joint between the hammer and the shank to fail as the wood in both the hammer and the shank shrinks.

The felt in your center pin bushings will wear much faster as it dries. The result can be the center pins becoming too loose and even beginning to walk out so you can see them on the sides of the hammer shanks. If the pins walk far enough they can completely disengage with one side of the hammer shank, and then your hammers will really wobble around, enough to actually hit neighboring strings.

Soundboard

The most obvious effect from the drying of your piano occurs in the soundboard. As it dries out, its crown will begin to collapse. With less upward pressure on the strings, the piano will not only go “out of tune” but the pitch will begin to drop precipitously. The first to go is the low tenor, in the area just above the bass/tenor break. If you play an octave such as A1 and A2 (the second and third A’s from the bottom) on a larger piano (or any other octave which crosses the break) and it sounds out of tune, the odds are very strong that it is the upper note which has moved, not the lower.

By the time the pitch drop extends a little past A4, (the A about middle-C) the entire treble will begin to go out of tune, sometimes in a very chaotic manner.

As the soundboard continues to dry, cracks, which were invisible in the summer, will begin to open up. The glue joints between the ribs and panel may also fail. In the most extreme cases the soundboard may actually come unglued from the rim.

Pinblock

The most damaging change occurs in the pinblock which is located under the harp. All summer the pinblock was been full of moisture and swollen; crushing the wood fibers against the steel tuning pins. Now, after the deep drying cycle, the pinblock has given up much of its moisture content and the tuning pins and the screws can become quite loose. If an actual crack develops in the pinblock, the piano will become un-tunable and will need a new pinblock.

This is just a short summary of what our pianos experienced after the extreme cycles we have recently gone through. Feel free to give me a call or drop me a note to discuss any unusual things going on with your piano.



My Soundboard is cracked!! My piano is ruined!

This is another great myth of the piano. While cracks, or more accurately: breaks, are unpleasant cosmetically, they usually are meaningless musically.

But before we go any further we must be sure we all know where and what is a soundboard and why it cracks. If you look under your strings in a grand piano or at the back of your upright behind the posts you will see the soundboard.

This mysterious piece of vegetative product is the most misunderstood part of our favorite instrument. The soundboard is made up of fletches of quarter-sawn sitka (usually) spruce. Traditionally tight grained spruce is preferred but with the loss of such old growth trees wider grain spacing has been used more in recent years and increasingly multi-laminate wood products (plywood).

The function of the soundboard is to take the energy from the string through the bridge and transduce that energy so that enough air is moved we can hear the sound. It doesn’t amplify the sound. Amplification implies energy being added to the system. The soundboard actually increases the rate in which energy is used. Without it, the string would vibrate softly for a very long time, slowly using up its energy. The soundboard uses the energy given to the string by the hammer at a faster rate allowing a large enough mass of air to be moved to produce an audible sound.

The soundboard has three primary components; the bridge receives the energy from the strings and provides contact with the soundboard. Underneath the soundboard panel are the ribs which move the energy across the grain of the panel and support the crown or upward bowing of the panel.

There are two methodologies for constructing a soundboard, for today’s purposes we will ignore the more modern method and look at the traditional method of soundboard construction. Traditionally the soundboard panel is dried to a level between 4% and 5% EMC (equalized moisture content) which is simply a measure of the water present within the wood. The panel shrinks in this process. The ribs are then glued onto the panel, perpendicular to the direction of the grain. As the panel absorbs moisture it expands and literally bends the ribs. The ribs prevent the panel from expanding across the grain on the bottom of the panel. The top side is freer to expand and expands more. The effect is the crown of the soundboard. The crown provides the soundboard positive resistance to the downward pressure of the strings.

Both the top and bottom sides of the panel will be in a permanent state of compression. Through the normal environmental swings the levels of compression will rise and fall with the relative humidity. Two things will occur over time from this situation. The first is compression set. While initially the wood fibers expanded and contracted within their compressed state, eventually they will take the compressed state on permanently. After being compressed one too many times during a damp season, during the following dry season the soundboard will release its excess moisture but because the wood had suffered compression set, instead of relaxing intact it breaks along the compression. Sometimes you can feel a compression ridge on your soundboard. This is a grain of wood which has been pushed up during an excessively high compression period. It does relieve some of the compression but you are looking at next winter’s crack.

So that is where cracks come from, what do they mean? Initially they mostly represent just a loss of surface area on your soundboard. In most cases we are talking about a .1% loss. In other words it means nothing. As more cracks develop the soundboard will lose more if not all of its crown which usually sounds like a warm, long sounding piano without much punch. Even a very bad board will still act as a transducer.

However if the ribs break off of the panel, you can see this as a gap between the rib and the board from the bottom or a raised portion along a crack on the top, you can develop some very loud buzzing as the rib, panel and glue residue vibrate against each other. This condition is very repairable and the soundboard can continue in service for many more years.

If you have any questions about the condition of your soundboard or piano, just drop me a note.

Andrew Remillard
President
ANRPiano.com