WarmGlass.com

Aluminum oxide breaks down - the particles round off - and is then less effective. Silicon carbide shatters and the particles remain sharp and still cut well (It's fun to watch the light show from the static sparks). It cuts faster also. However, If you work large heavy pieces and have to shlep them around, carbide dust is very abrasive and you get lots of fine scratches when you handle it (as in hefting heavy pieces around). Savoy studios used Aluminum for years to reduce the scratching but switched a few years ago because they do a lot of deep carving and time saved is money saved. I guess they have solved the surface scratching problem.

Raf

I use 170 grit al oxide I buy from Graingers. Most board members use 120 grit (I believe.) I don't do much blasting, mainly for getting that nice fingerprint-free leather-look on plates & bowls or to knock off a piece of kiln brick that drops on a piece before slumping.

The 170 looks like powder and is pretty gentle. I would assume 120 would have a rougher texture and would cut faster. I've never used 120-sometime I'd like to try it. My schedules are all dependent on the 180 so I'd think I'd have to adjust them for the rougher grit.