Hi,
Ya have done some experimenting with both corb cob and walnut media, and few different additives: Flitz, Semi-Chrome, Blue Magic. Also have used Linde A which is suppossed to be 0.5 Micron Aluminum Oxide and also a pack of hobbist polish which I assume was 50 Micron Aluminum Oxide - however not sure if it was aluminum oxide or not. Have some 50 Micron Alum Oxide coming and some 50 Micron Silicon Carbide coming.
With the Walnut and Corn Cob media, trying each with Flitz, Semi-Chrome, Blue Magic and finally a run with Linde A - seemed to get to much what I would call surface burnishing/scratching - the media does scratch the surface! Got some smaller grain corn cob 20/40 mesh and the scratching was far less but still apparent almost gives the surface a kind of frosted appearance - thinking about trying some 100 or 200 mesh to see what the difference is.
Also considering instead of using a solid/dry setup going to some sort of a liquid - it would seem if you were to flow water or ? through a system with something like Linde A powder suspended in the solution using the forces created by the vibratory machine it should polish the piece and wouldn't have to be concerned with solid objects pinging into the aluminum.
Anyhow have spent some time researching different companies and web info and get conflicting information so will just need to keep experimenting. Worst case can employ the vibrator in a middle step - will still speed things a bit.
Was hoping would be able to just get some walnut media, throw some Flitz in there and VIOLA! but guess not!
Oh well keep playing!