How do you get yellowed ivory piano keys white again??
We have determined that ivory turns yellow in the dark. Keep the key cover open so that the keys will be exposed to sunlight. This will not likely improve the present degree of yellowing but it will help to prevent further discoloration.
As far as removing the yellow, it depends how deep it has gone. Sometimes just rubbing them down with 0000/steel wool (very fine) will help. If that does not help it would be best to have a piano technician evaluate the situation. The ivory may have to be taken down quite a bit to remove the yellow. I don’t recommend you attempting this yourself.
We also found information about cleaning piano keys (ivory) using 600 grit emery cloth, then 1500 grit (not always available), after which using “elbow grease” and Brasso. I would question this method, as most of the information we read, cautioned against using ANY aggressive chemicals, especially liquids.
It should be noted that for most ivory jewelry and many pianos, the yellow patina is valued, as it only comes with age. In some cases, cleaning can halve the value of the piece.