For those of you needing a quick and easy way to restore the blackness to your gray, faded Delrin parts, I’ve found the perfect solution. The Simplex bracket on my newly acquired PX-10 was cracked when I bought it. A non-broken replacement bracket was donated to the cause, but like the original, had faded to an ashy gray.

First, I disassembled the derailleur as far as possible. The lever arm appears to be riveted, so it, the piston, and spring were left in place. Then everything got a thorough cleaning in the tank of mineral spirits.

Once completely dry, I gave the Delrin body a few quick sprays of Chemical Guys Black on Black, rotating the part until every side had a light coat. The Delrin turns black as soon as it’s sprayed, so it’s easy to tell where you've sprayed. Then just wipe it down and you’re done. Overspray won’t hurt or stain metal, glass, or paint as long as you wipe it off when you’re finished.

I used it on the Delrin shifter nuts last year on my Gitane and they’re still black after many miles.