500 AO vs 500 SC

Hi Scott, the main differences:
Brown AO is great for vibes, flat-laps & crap for rotary tumblers, it breaks down in about a day or so with Moh's 7 stones.

SC is a general purpose grit with no major faults other than it breaks down in about 3-4 days in a rotary with Moh's 7 stones.

White AO lasts about double the time as SC in a rotary with Moh's 7 stones & it has a similar crystaline structure to SC & is a few points harder than SC!

What do you use for grit?

The difference between Silicon Carbide (SiC) and Aluminum Oxide (AlO) is that as the SiC particles break down they expose new cutting edges that remain sharp. So eventually your 500 SiC will turn into 1000 SiC which potentially could be a good thing if your rocks are ready to graduate from the 500 SiC stage. AlO particles are more round and perhaps offer a more gentle polishing action. I've never used 500 SiC but perhaps someone around here has used both 500 Sic and 500 AlO and can offer some opinions.

The color of some types of grit is very telling. Pink Cerium Oxide is optical grade. White Cerium Oxide is a much finer particle and as such will provide a better shine. In this case, were talking about 500 grit AO. The dimension of the particle is a known quantity. We're talking about the same molecule (Al2O3). So I assume that different colors would indicate different size particles or perhaps differences in purity. I would also assume that it would break down at the same rate as well.

Yep. SC is harder than AO. I think sometimes color is added to help distinguish the products. SiC breaks dowwn into sharp shards and AO tends to round off and stop cutting. I examined a sample of SiC grit before and after a few days of tumbling, comparing 60-90 to 150/220, under 50 power magnification. The SiC did indeed shatter revealing new cutting surfaces. We discussed this in a thread a few mmonths ago and it generated a lively discussion. For most purposes, ythough, I think the two grit sizes should give comparable results. I have decided I definitely need to use a higher grade cerium oxide on my stonees or burnish thm all as a matter of routine. I'm not getting the shine I should on some materials, particularly the softer ones. Generally I use 600/700 SC as a prepoklish nd may add another step with Lusteritr prepolish (Graves' AO product) and see if it helps.
Mark H.