I suppose the back of my GlassStones counts as
`in-writing'...

1000 mesh - 14.7 micron
2000 mesh - 7.35 micron
4000 mesh - 3.68 micron
8000 mesh - 1.84 micron
16000 mesh - 0.92 micron
30000 mesh - 0.49 micron

- Scott