I tried dousing it with WD40, which seems to have produced a reasonable result .......... not black, but “blacker”.If its not too far gone a coat of mineral oil or if you dont have that some olive oil will make it blacker...but not jet black.
Dont use veggie oil, it can start to smell
apply with cloth or paper towel, If it sucks it up after 10 minutes you can apply again.
Wipe it down and play.
If you wash it with soap and water it will likely reverse this process.
If it's not over important on what happens to the appearance of your Mouthpiece try some wire wool, (the finest grade) or a very fine grit silicon carbide grade Emery type paper, around 7000 grit, but not on the table or rails.I have an oldish hard rubber Otto Link Tone Edge 6* which is now virtually olive green. Does anyone have any magical tricks to enable me to restore it to its former black ? It still plays well, but looks a bit weird.
I use the wire wool to polish copper, it's liberon 0000If it's not over important on what happens to the appearance of your Mouthpiece try some wire wool, (the finest grade) or a very fine grit silicon carbide grade Emery type paper, around 7000 grit, but not on the table or rails.
there are several mouthpiece makers like Ponzol, Jody Jazz, Drake, Lamberson and SR Tech who use other materials for some of their products eg Resin, Acetal, Delrin, Polycarbonate - but for some reason the saxophone industry is stuck in the past and hard rubber is still used because that's what they used for the vintage mouthpieces that are so fetishised these days..It'd be great to have a mouthpiece as comfortable as hard rubber but without the color and odor issues