Every time you play a note on your piano, the felt hammer depresses down onto the string, striking it to create sound. This happens over and over again as your fingers run across the keyboard pressing down note after note.

In all pianos, vertical and grand, the felt hammers become grooved over time from this action. As they strike against the string, it compresses the felt just a little. Over time, this can begin impacting the sound your piano makes.

If your piano is rarely played, this process may take decades. If your piano is heavily played, it may take a few years. And if your piano is used daily in a practice room at a music school, for instance, the time frame may shorten considerably.

When hammers are new, only a very small area of the hammer is striking the strings. As the grooves begin to wear into the felt, a half inch or more of the face of the hammer may be striking the string every time it is played. This can cause a harsh and uneven tone.

If you open up your piano and look down at the hammers, you will notice the grooves in the felt, with almost a dirty or heavily worn look to them. The hammers should not be fixed so they look “clean”. Cleaning the felt will not fix the problem. Some attempt to take off a thin layer with a dremel tool to fix the problem, yet this is largely a cosmetic fix that will not impact the overall tonal quality. Others have even attempted to clean the felt with soap and water; this only risks further damage to your piano.

An experienced piano technician can recontour the hammers, restoring them back to original shape. The hammers are “filed” in such a manner as to take off very thin layers of the felt until no string grooves remain. This allows the original curve of the hammer to once again take place.

Keep in mind that the felt hammers can only last so long, even with regular maintenance and recontouring as needed. Eventually the hammers must be replaced.