Check out the picture of the piece of aluminum bar stock in this article:
http://www.nasatech.com/Briefs/Feb01/GSC14147.html
I've seen several posts throughout this forum in the past about guys who had exhausted all sandpaper grits, gone through all the various compounds, and after it was all said and done there were still tiny scratches that would show up on the part when looked at from the right angle and under the right kind've light. My guess is after looking at this process Nasa used with India Ink, and seeing the end result, maybe this last step might be worth the extra trouble? (I mean heck, if you're already soiled from compound gunk flying around, what's a little ink gonna hurt?
)
Just out of curiosity has anyone here ever experimented with this stuff?
-Rob-