My bass-playing son uses a plectrum (I don't). He 'borrows' my basses occasionally and black scratchplates, especially, can appear a bit worse for wear when the bass comes back. Just wondered if there's a miracle cure out there? Thanks folks.
Snork
Take the ball-end of your thumb and with the bass tuned to pitch, press hard on the E string just the fretboard side of the saddle. Tune the E to pitch again. Sometimes an E string needs to have that slight 'kink' in it to sound properly. Hope this helps you.