The description of the piano was great and the price ok. However, after I picked it up at the owner and came home, I realized that the description of the state of the piano was not completely true:
- 4 of the keys were hanging down 0.1 inches and did not make a proper sound.
- all of the keys apparently had an ugly incident with some kind of aggressive cleaning agent, because their shiny surface had lots of dim areas that looked like stains.
Step 1: What You Need (Apart from a Looooot of Patience)
They all suggested polishing with car polish or something similar! So I went to a DIY store and finally bought a "repair set" for acrylic bath tubs. The set contained sand paper ranging from 400 to 1200. ( I am not sure if you have the same classification of sand paper in the US, for us 1200 is really super fine, it's pretty much the smallest grains you can get). Furthermore, the set contained a polishing paste and a polishing towel.
Additionally, I also bought a "sand towel" with 1500 graining which is the finest sanding available.
I also bought a fixture for a round plate and a lamb wool towel to put onto the fixture. The whole thing could then be attached to the drilling machine.
In addition, I also bought PTFE paste (teflon / silicone paste) to lubricate the moveing parts of the keys again after I removed them and put them back.
Apart from that, you need a drilling machine, screwdrivers, a loooot of time and a room where you can store all the removed keys and the rest of the piano pieces.
Step 2: Remove the "Wrapping" of the Piano
Watch out: The back side of the keys has a lot of grease on it to lubricate the movement of the keys. So make sure that your pillows underneath are protected once you flip the piano on the back side.
- Remove the connecting board of the legs
- Remove both of the legs
- Place the piano onto some pillows to assure you don't harm the keys or buttons when you flip it over to unscrew the rest
- Unscrew all of the screws on the back side
- Unscrew ONLY the screws at the borders underneath the piano (not the ones around the black squares in the picture)
- Unscrew 2 side screws on each side
- Remove the whole back side (including the sides)
Step 3: Remove the (Broken) Keys
- Make sure you move the front panel a bit away from the keys (or the keys a bit to the back)!!
- Start with the white keys, the black ones can only be removed after the white keys around them are already removed.
- Take two screw drivers and position them inbetween the "wings" of the key, as shown on the first picture
- Gently wiggle around and spread the screw drivers apart until the two tiny cylinders of the key come out of the fixture
- Then, slowly push the key to the front and remove it.
Step 4: Fix the Broken Keys
The ones that were hanging down were really broken (see first image below), but also many of the other keys were affected (see second image). Especially in the normal C-major range. (Later it turned out that a 6 year old child owned the piano and she had quite a temper).
To fix the keys (hammers) we did the following:
- Remove the broken hammers from the piano (make sure you don't forget where they belong)
- If the black foam rubber piece is destroyed (as in the first image) remove it and go to point 3 in this list.
- If the foam rubber piece is still intact (without much dents) go to point 7 in this list.
- Cut felt pieces with the same size and thickness as the foam rubber before (approx. 1 mm / 0.04 inches). I took pink ones, so you can easily identify which hammers I fixed.
- If the plastic piece is gone (like in the first picture) cut a plastic foil (like from a plastic binder or a transparency foil) piece the same size as the foam rubber piece.
- If the plastic piece is still there and intact, reuse it.
- Put (fiber reinforced polyurethane) glue onto the top of the hammer (see 4th image)
- Shortly put the felt onto the glued area and remove it again. Let it react with air for 5-10 minutes. Then put it back onto the glue and press it together for a few minutes.
- Add another layer of glue onto the felt or the intact foam rubber piece.
- Quickly put the foil onto the felt, remove it, let it react with air for 5-10 minutes and then put it back onto the felt and press them together for a few minutes.
Once the hammers were fixed, I noticed that some free floating felt stripes were distributed inside the piano. I learned that these stripes are supposed to damp the "impact" of the metal piece of a hammer once it's pressed. In order to glue them back to where they belong, i build a little helper out of a piece of cable. I folded the cable once and then bent it like a finger. (see image on ugly green carpet).
Then i looked for a position where two octaves meet because there is more space (bigger hole) for your fingers. Then, put glue onto the felt and press it with your finger onto the part where it belongs (see image). On the right and the left side of the bigger hole you can use the cable helper to press the felt onto the piano.
Step 5: Sort the Keys and Polish Them
I also tried to polish the bad spots with a Dremel polishing head, but I can not recommend that, since the place in contact with the dremel becomes really hot and melts the plastic of the key :(. Furthermore, the lines left by the dremel are also quite hard to polish afterwards. So: no Dremel, more hand work :).
- Firstly, I sorted the keys into two categories: severely affected and slightly affected
- Label the keys with numbers. I took a water proof marker and labeled it on the side of the keys! The polishing paste will polish away your labeling if its on top of the key.
- Cover your bath room (or wherever you work) with news papers or a plastic foil or something. The spinning disk will throw tiny drops of the polishing paste EVERYWHERE! I, therefore, also recommend wearing an old shirt or something, and protective goggles (or just glasses).
- Then, I started with the severely affected keys.
- Sand them with the finest sand paper you can find, or maybe even a "sand towel". The finest sand towel I could find was 1500.
- Make sure to move the towel very evenly and with no pressure! After a while, the key looks uniformly dim without deep scratches.
- Then take the drilling machine with the lamb wool fixture. Put a few pea-sized drops of polishing paste on it (or onto the key) and slowly turn the disk. Press the key as gently as possible (not so gentle actually :)) onto the rotating disk with lamb wool.
- Increase the speed and make sure the whole key is being polished. You can check the surface by washing it with water and dry it with a non-scratchy towel. If it still has dim spots or scratches -> keep on polishing.
- Once it's shiny, rinse the keys with water and take the soft towel from the "repair set for acrylic bath tubs" (or any other super soft towel) and put some of the polishing paste on it. Polish the keys with this towel.
- Rinse the keys with water and dry them.
- Now, take the slightly affected keys and polish them directly with the lamb wool drilling thingy :). After that, polish them with the super soft towel as described above.
- Sort them according to your labeling first.
- Put PTFE paste onto the back side of the keys.
- REMEMBER to put the black ones first, then the white ones!