The pinblock (or the wrestplank as it is sometimes called) is the block of wood that is behind the plate of the piano and holds the tuning pins tightly. The pinblock must be built strong enough to withstand the cumulative force of all of the strings pulling on the tuning pins. Each tuning pin is attached to a string which is under about 150 to 200 pounds of tension, and the complete set of strings is under anywhere from 20,000 to 40,000 pounds of tension. The best pinblocks are made of quartersawn hardwoods, with beech and maple being the choice of most piano makers. Originally the piano did not have nearly as much tension on the strings, so the pinblock only had a few layers. However, the modern piano has between 9 to 21 layers of top-quality wood in its pinblock, because of the extreme forces it needs to counteract.
The pinblock must be precisely drilled and each tuning pin installed to get the proper amount of friction. If a piano is designed with a large amount of friction between the tuning pins and the pinblock, it will be difficult to tune. If a piano has too little friction between the tuning pin and the pinblock, then the tuning pin will not hold the string tightly enough to stay in tune. But if there is the proper amount of friction, the piano will tune easily.
As a piano ages it often suffers from extremes in temperature and humidity, which can cause the tuning pins to become loose. This happens because the wood of the pinblock shrinks and the size of the hole into which the tuning pin is installed expands. If only one or two tuning pins are loose, an appropriate repair is to remove the tuning pin and to replace it with a larger sized tuning pin, or to install a shim in the tuning pin hole. Either of these repairs will provide enough friction to allow the piano to be tuned again.
But what does one do if a whole set of tuning pins is becoming too loose because of a weak pinblock? A repair which is sometimes done is to apply a "pinblock restoring solution" which will restore moisture to the pinblock and allow the tuning pins to be held tightly enough to hold the string in tune. There are several problems with such an approach. First, the solution which is applied often does not soak down into the pinblock, but rather flows into the space between the plate and the pinblock. Second, the mixture can leave a dark colored sticky residue on the plate and tuning pin and strings. Often this solution will cause rust to form on the tuning pins and strings. Third, the solution only provides a short-term solution and is not permanent. In just a few years the piano often has problems with loose tuning pins again. It is true that this "pinblock restorer" will allow a piano to be tuned, but it often is difficult to achieve a fine tuning on a piano that has been treated in this way. In my opinion, a repair using the application of a pinblock restorer is only suitable for pianos that are not worth the cost of doing the appropriate repair, such as installing larger tuning pins, or installing a new pinblock.
A better repair for a piano that has loose tuning pins is to install a set of larger size tuning pins. This repair is completely satisfactory as a permanent repair for most pianos. In fact, when rebuilding an upright piano, it is usually not feasible to replace the pinblock, so replacement of the tuning pins with a larger size is usually recommended. Replacing a complete set of tuning pins is an in-home repair and can usually be done in one day. Of course, if the piano were also being restrung with new wire at the same time, it would be better to remove the piano to the shop. If a piano already has large oversized tuning pins installed and the tuning pins become loose, there are two options. One option would be to use epoxy to repair the damaged wood of the pinblock. Another option would be to drill the pinblock and install pinblock plugs. Both of these repairs often allow the use of the original size tuning pins once again.
There is a new pinblock repair that has received favor in recent years. Often a set of tuning pins may become loose very quickly as a result of the low humidity associated with winter heating. In such cases, these pianos need a complete humidity control system to be installed within the piano. Once the moisture content of the piano has been raised to normal because of the humidity control system, the piano can then be tuned without the need for further repairs. The best humidity control for a piano is the Dampp-Chaser Piano Life SaverŪ humidity control system. I am fully trained in the installation and maintenance of Dampp-ChaserŪ components and systems.
The best thing to do for a piano that has a deteriorated pinblock is to replace the pinblock. This falls under the category of rebuilding, rather than repair, because it involves complete disassembly of the piano, installation of a new pinblock, and complete reassembly of the piano. The pinblock is drilled to receive new tuning pins of the original size tuning pins and usually has new strings installed as well. Because of the quality of materials available today, often a new pinblock can be fit and installed that is better quality than the original pinblock material. A piano that has a new pinblock properly installed can often be expected to last another 40 or 50 years if the rest of the piano is rebuilt as well.
The plate of the piano is an important structural component. It is designed out of cast iron to be able to counteract the tremendous forces acting on it. The strings of a piano individually have from 150 to 200 pounds of tension, and the cumulative forces acting on a piano can be anywhere from 20,000 to 40,000 pounds. The plate has to be securely fastened to the wooden framework and the rim to keep the piano from coming apart from all of the stress.
One common problem is that the plate begins to pull away from the rest of the framework of the piano. If the pinblock is weak, the screws that go through the plate into the pinblock can become stripped and even begin to pull out of the wood of the pinblock. In a case like this, the piano is not tunable, and needs to be repaired before a tuning is possible. The most common repair is to remove the shorter plate screws and bolts, and to install new carriage bolts that will go all of the way through the plate and the pinblock. Once the plate is securely fastened again, the piano can then be brought to pitch and tuned.
Another problem that can happen to a plate is for the plate to have a crack or a break in the cast iron. This is a source of tuning instability, because if the plate does not hold the framework rigidly, the strings surrounding the plate break will be unable to stay in tune. The repair of a broken plate is quite costly and usually involves complete disassembly of the piano. The plate is then taken to a welder experienced in welding cast iron. The whole plate is heated until it is cherry red, the weld is completed, and then the piano is allowed to cool slowly to room temperature. Once the piano has been reassembled and the strings are once again brought to pitch, the plate will usually hold up for many years. However, there are NO guarantees with this sort of repair. Sometimes after the repair, the plate will crack again once it is brought up to pitch and tuned. It is possible to weld a crack in the plate with the strings on and the piano up to the correct pitch, but once again, this is risky and there are no guarantees.
The last problem with a piano plate is purely cosmetic. Often during a complete rebuilding of a piano, the plate will be cleaned and sanded, and then coated with several coats of bronze and clear lacquer. The decals and pinstriping and other artwork will be carefully replaced to make the plate look like new again. In some cases, the plate will have irreplaceable artwork that must be carefully cleaned and protected and then coated with a clear coat of lacquer. A good refinisher can do outstanding work to make the plate highlight a complete rebuilding job.