I like watches, and the type I typically go for are the relatively inexpensive, "high-feature" type. I've got a Casio Wave Ceptor as my main wristwatch right now; I've had Timexes with the built-in electronic compass, and a host of other ones.
Trouble is, the plastic crystals don't hold up well to my wrenching lifestyle. I'm always forgetting to take the watch off, then squeezing my arm into some tight spot in the car, and invariably I scratch the bejeezus out of the crystal. After a year or so, the watch looks like it was attacked by a herd of tiny cats.
Of course, these are inexpensive (<$100) watches, so my remedy in the past has been to get a new one once they start looking crummy. But I really really LIKE my Wave Ceptor, and so I started wondering if I might be able to fix it up somehow. It was very scratched up, and getting hard to read.
Well, I've come up with the answer: sand the crystal. I started out with 3M Wet-Or-Dry 600 grit sandpaper to take down all the scratches. After a little sanding under a steady stream of cold water, I then moved up (down?) to 3M Wet-Or-Dry 800 grit. I polished some more like that, and then finally hit it with 3M Wet-Or-Dry 1200 grit. This will bring you close to the final finish you're looking for. Remember to keep the stream of water flowing across the crystal while you sand, and use an orbital sanding motion -- try to keep the pattern as random as possible.
Finally, finish it up with a jeweler's rouge cloth. Use the red (rouge) side first, then polish it up with the yellow side.
I tried it on an old watch first to see what would happen, then took the plunge and polished up the Wave Ceptor. It worked great! It remains to be seen if I've taken off any layer(s) of anti-scratch coating -- it might scratch right back up even more quickly -- but for now, the crystal looks almost as good as a new watch's.
