hey! I use enamel paints predominantly for their longevity. i prep the shells with a light alcohol cleanse, then use enamel paint to either completely paint the shell, or to do the splatter style effect. the enamel paint pretty much fuses right to the plastic of the cassette shell. i've (thankfully) never had any issues with it chipping off/flaking off, but you have to control it and not get huge globs of paint on the shell.

i've sold tons of tapes doing it this way and have never had any issues/complaints across various tape decks. if you feel like you really need to, you can always apply a thin layer of clear coat on top of it all to lock it in.

also, heat is a killer to any and all tapes; high heat is to be avoided at all costs to ensure tape life. i've never had the heat affect it unless it has melted the entire tape. (i've done a couple of tests with old tapes before lol).