Sat Mar 17, 2018 12:29 pm
I would caution you on using sandpaper, especially starting with 400 grit sandpaper.
400 grit sandpaper is likely too coarse, especially if you're trying to eliminate the smooth sheen on polished plastic. I think you'll quickly regret trying 400 grit sandpaper in the beginning. (I hope I'm not replying too late.) You might end up with keys that just look all scratched.
Since you're starting off with a polished plastic, and want to dull the sheen to make it less slippery, I would start with a 1200 grit, test it out, then try the 600 grit if you're not completely satisfied with the result with the 1200 alone.
You should be able to find 600 grit at a local hardware store (I have Home Depot and Canadian Tire in Canada). 1200 grit is not available at regular hardware stores. It's hardly used by your average Do-It-Youself'er and is only used for specialized jobs such as polishing to achieve mirror finishes.
Your best bet is to get your hands on 1200 and 600 grit sandpapers (you probably only need 1 or 2 sheets), try sanding another object that is made of a similar hard plastic like the keys on your Rodgers organ (plastic toy, enclosure of discarded computer monitor, printer, etc.), and then decide which sandpaper is the best to start with. If you have another object to experiment with sanding, maybe you can get away with trying the 600 grit that is more readily available.
Just be careful... the keys are probably made of a thin plastic, so you can only afford to remove a tiny layer of plastic with the sandpaper. Going too far will be a costly mistake.
Any questions, feel free to ask.
Be sure to report back on how it turns out so that we can all benefit.
Good luck.