As your Piano Tuner Wilmington DE, I am often asked why pianos are so heavy.  Here is the answer: Looking at a piano, it appears to be just a piece of wooden furniture.  In fact, it is quite different.  Even though there are only 88 keys on a piano, most of the keys have three strings each, totaling over 200 strings per piano.  Each of those strings has approximately 150 pounds of tension each.  The reason for the high tension is that the sound is louder the higher the tension.  Pianos are designed to have enough volume to fill a concert hall.  If you multiply 210 strings times 150 pounds of tension, you will find that a piano has about 30,000 pounds of total tension.  If the piano were made entirely of wood, it would collapse on itself in a matter seconds.

Cast Iron Plates Reinforce the Structure of Pianos

In order to keep the piano intact and able to support all that tension, each piano has a cast iron plate for reinforcement. Cast iron is used because it flexes very little under tremendous loads, compared with other types of metal.  The disadvantage is that a cast iron plate weighs several hundred pounds.  Each string is directly attached to the plate at the far end from the keyboard, it is threaded over the piano bridge, and attached at the other end to block of maple that is securely fastened to the plate.  The plate then supports the structure, so the piano will not fold up on itself.

Pianos did not always have plates.  The full plates we see today date only from about 1900.  From about 1870 to 1900 there were partial plates in pianos, and before that there were no plates at all.  Early pianos were made entirely of wood and patterned after a harpsichord.  Gradually, string tension was increased on successive designs, in order to increase the volume of the pianos, so that the sound could fill a concert hall.  The increased tension pulled the pianos out of shape, so they were useless.  This was called being “in wind” (rhymes with “mind”).  The saying comes from the concept of being “wound up.”  To compensate, metal structures were gradually added over the years, culminating with the full cast iron plates that are used today.  The evolution of piano design, then, paralleled the industrial development of better ways of casting iron.

Your piano tuning Wilmington DE expert, Kenneth Keith Piano Services, is always available to answer your questions about pianos.