pencil graphization of keyboards?!

there are still miracles...
Lately, we rarely see "graphitization" with a pencil, but there are still exceptions and miracles.

A client bought a Commodore Plus 4 computer, saying the keyboard wouldn't work at all. You may think: of course, no problem, it needs to be re-graphited, and it will work. Well... if it's been graphitized with a pencil you can't do anything with it anymore.

We tried to wash it with chemicals and with ethyl alcohol on an earpick, but with no success. Even if it would come off by some miracle, the question is: will the re-graphitization remain permanent?

The final result: the keyboard replacement and the "graphitized" keyboard were used as parts, except the rubber contacts.

We ask everybody NOT TO graphitize with a pencil!