Re-gluing hammer felts on a grand piano

Last year my 1994 Mason & Hamlin BB (a 7-foot grand) developed a very unusual and alarming problem: several of the hammer felts in the mid-bass section came unglued. along the front side of the hammer. Thankfully the felts remained glued along the back side; otherwise they would have fallen off completely. My piano technician called the M&H factory to ask for advice, but since the company changed ownership after my piano was built, and the piano was out of warranty, he wasn’t able to get any satisfaction. So he took the action away for a week and re-glued the felts with hide glue. This was a quick and dirty patch job. The ideal solution is to replace all the hammers, but that’s a very expensive, time-consuming operation.

After I moved to Vermont in June, I hired a local piano technician to install a humidity controller in the piano (more on that later). He noticed that several other hammers had come unglued since the last fix. I described the California technician’s solution, and he said that just plain old superglue would do the job and that I could do it myself. He reiterated the warning that the affected hammers were already permanently damaged and that the whole set (all 88 of them!) should be replaced eventually.

So over the next few days I removed the ailing hammers and reglued them. Superglue doesn’t set very quickly in a situation like this. The hammer felts are porous, but are also extremely stiff and dense, and can’t be pressed back into shape by hand. I used a medium sized spring clamp with plastic-coated jaws that I bought at the local hardware store. The spring in the clamp was strong enough to overcome the felt’s stiffness and keep it pressed into place for a few hours. This hack seems to have worked for now; it’ll be interesting to see how long it lasts.