Last time we looked at all the steps required to clean and restore the key bed of our antique piano project, which sits underneath the keys. Now, I'm going to show the process of restoring the keys themselves. The main process taking place is called rebushing, which involves replacing the key bushings, or little felt walls, with brand new felts and glue. But first, I had to start off with a very important organizational step: numbering the keys.
At some point in this piano's work history, a technician scratched numbers into the keys to signify each key's place in the piano. Each key is cut a specific way that could only properly fit in its spot, if the keys were to be jumbled it would take a very long time to figure out what key goes where. I've actually seen a piano that was having an issue with two keys that were getting stuck during the play, and the issue was just that at some point they had been mistakenly swapped. So, since I want to avoid any hassle, and since the numbers were somewhat faded, I wrote in new ones to be safe.
After finishing that first step, I did a quick vacuum all across the keys, and I wiped and scrubbed them with vinegar and water. While I will end up replacing these keytops in the future anyway, I didn't want to be working on keys with 100-year-old dirt caked on them. It ended up taking longer to clean them than I expected, as I also had to scrub the dirt off the sides of the keys. After cleaning them I took a look at the chips on the keytops. The chips are why I will eventually be replacing the keytops; while I like the look and feel of the original tops, the extremely brittle plastic will continue to chip, so even if I were to just replace these ten that have issues, more may break in the future. I will send them off sometime soon to get a full, modern replacement, with pristine plastic that won't stain or break nearly as easily as these. Note that I will not be replacing the entire key, which includes the wood underneath, but rather just the plastic tops.
With the keys clean, I moved on to possibly the most satisfying step: polishing the capstans. The capstans are the little screws at the end of each key which are used for regulating lost motion. I'll touch on that down the line, when the piano is assembled again and ready for a full regulation. The capstans are usually made of brass and are in constant contact with the underside of the action, rubbing against it each time the key is played. Over many years of play and different environments and humidity levels, dirt gets on the capstans just like the rail pins in the last post about the key bed. This dirt, if left alone, can create a sluggish feel during play, so I polished them with soft steel wool and lubricated them.
The next process was a simple one, but it had to be done before rebushing, in case I dripped any glue onto the new bushings. Some cracks had formed right on the space that holds the bushings, called the mortise. Since the wood of the key is weakest at the mortise, I had to fix it with a specialized glue that dries hard like plastic and is great for porous surfaces like wood. I dripped some thin glue into the crack, and then clamped it down so it could dry, bringing the wood together and sealing it. This process ended up having to be done for two keys.
Now it's time for the final step of the keys: rebushing. This is a very complicated and extensive process, requiring specialized tools made for working on keys, as well as lots of patience. Every key has two sets of bushings, for the front and the back. This is because each key pivots on two points, which are the front and back rail pins. If the key did not have these felt bushings, then the key would make a scratching metal-on-wood noise every time it got played. If the space was completely open, the key would have a significant amount of wiggle room, enough to interfere with play. So, the felt is necessary, but felt also wears down and hardens over time. This is the case of our Vose and Sons, where the felt is so old it almost has the same color as the wood, and it makes a knocking sound when it gets moved left to right.
The pictures above show the process of taking out the bushings, which had to be done for both the front (underneath the keys) and the back (the top of the keys). The process is done with a steamer, which moistens the felt and melts the glue, allowing for the old bushings to be pulled out with tweezers. The last picture shows the pile of old bushings, front and back. After this was taken care of, I could move to putting in new felts.
The process starts with one specific tool, called the Bushmaster. It has a wedge designed for pressing into a line of felt and pushing it down just the right amount, and a spring-loaded blade designed for cutting that felt. I first layer wood glue into the empty mortise with a toothpick, as much as I can put without it dripping or soaking through the felt when I insert it, and without placing it too far down. I then layer my strip of felt (I used two different sizes for the front and back) over the mortise, press down, and cut with the Bushmaster. After quickly putting in a caul, I'm ready to move on to the next key. The cauls are specifically sized to be slightly bigger (.002 inches) than the pin they are imitating. It fills the entire mortise and presses the felt into the glue, so it dries cleanly and presses down on the top to do the same. I have multiple sets of cauls for each piano I encounter that needs this service, as different pianos have different sized pins. I then rinse and repeat for all 88 keys.
After finishing rebushing for both the front and back mortises, I cut the unglued felt strips with scissors and then with another tool I cut the bushings flush with the wood. Rebushing is one of the arts of the piano world, requiring lots of practice, special tools and sets of cauls and felt. Afterwards, you can see a huge difference. The red bushings stand out on the keys, and they feel much nicer and more uniform in the piano. This service goes hand-in-hand with the rail pin polishing I did on this piano. With brand new bushings and newly cleaned pins (and a properly regulated action), the keys should all feel exactly the same during play, which is necessary for any performance-level instrument. After putting the keys back in the piano, I'm ready to use my workspace for something different, which you'll have to wait until next time to see.
If you feel like your keys are sluggish while being pressed down or while returning, or if you notice a lot of wiggling side to side, give us a call! This isn't something I would recommend anyone but a learned technician doing, as it is extremely tedious and easy to mess up without practice and the proper tools. With 88 keys, and 2 mortises, and 2 bushings per mortise, you end up with 352 individual pieces of felt that need to be taken care of. I absolutely love doing it though, and I can't wait to play the finished piano!
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