I've had to clean a few hundred knobs from big recording consoles. I take the knobs off (after making careful notes about locationWhen people tell me to use nail polish remover on plastics, just remember in essence, nail polish remover is a form of acetone which in many cases will affect plastics and acryillics. I would not suggest that and in fact Goo gone can be harmful too on plastics. I am a model train enthusiast in N scale and have to be very carefull when using these products around plastics. FYI. Suggest using alcohol.