Rio now has the 3M one and six micron radial bristle polishing discs.
I am adding an e-mail response from Rick Pihl to my question about
how the pumice grit size compared to the six micron polishing disc.
John, Some info from the Pumice manufacturer: FFFF is the grade of
pumice. Typical Screen Analysis… in this grade there is a Trace of 74
micron particles (Trace = less than .05 grams for a 100 gram lot) 16%
is 44 microns 84% is PAN (less than 44 microns)
Hardness on MoHS = 5.5 to 6.0
Pumice is softer, more brittle and porous than the polishing compound
in the 1 and 6 micron discs.