[Sound Mind]

@David M - I did was thinking sandblasting/sanding at first, but I immediately started worry about either accidentally grinding the tape away and ruining a fine edge, or when painting it, the paint would pool in a groove and also ruin the edge. So I figured I'd ask for simpler ways first, to see if there were any.

@Bailey - Saliva is partly hydrochloric acid, though it's very, very diluted. Otherwise you'd digest your own mouth. Highest concentrations are found in the stomach. And even there, it's fairly diluted. Also, it would suck spitting on an acrylic sheet for hours. :-P

@Strider - That's an interesting idea... If I can find some for a good enough value, I might give it a shot. I figure I may as well paint the whole acrylic piece first, then mask off the center and paint the rest black. If that'll look good, that definitely sounds like the simplest way.