Thanks David. I looked at the labels again and you are 100% right about the listed materials. I'm not sure why I was able to get the typical darkening of the strop that had blue compound on it but it might just be dirt rather than metal. The green is working like a champ but I want to experiment with a finer compound after the chromium oxide. Any suggestions? Also, is there a traditional "color coding" of compounds used by most manufacturers?
The only super-fine compounds I'm aware of (for steel), are the sub-micron diamond and maybe CBN (Cubic Boron Nitride). They will also be more aggressive cutters, as they're both significantly harder than the green compound. Being that they cut more aggressively, it may be hard to predict if they refine the finish beyond the green compound, or not. They can be had in sizes finer than 0.5 micron, but I don't know if they'll perform accordingly.
As for color-coding compounds, I don't know if there's a set standard. I sort of doubt it. Having said that, usually the black will be silicon carbide (extremely wide range of grits, any of which could be black), the red will usually be iron oxide, and green is almost always chromium oxide (and ~0.5 micron average particle size, at least from reputable brands). Most of the time, I think white will be aluminum oxide (again, a very wide range of grit sizes, all of which might be white). There are other 'white' compounds out there, which aren't aluminum oxide, but some other abrasives usually suited for softer metals like jewelry. In fact, there are several colors out there of 'jeweler's rouge', which is normally red ('rouge' is the French word for 'red'). One of the sites I looked to earlier, in reading about the blue compounds, actually referred to it as another form of jeweler's rouge. There are also mixes of compounds on the market, like a mix of chromium oxide + aluminum oxide. That introduces a whole new range of ambiguity.
