[ATM] Clarifying the Sharpie Test

[peter at kitgear.com (Peter)]

At what grit should the Sharpie test show perfect removal of the Sharpie
lines? I've been working an 8" mirror (TOT) with #220 grit for hours and the
central 50% of the mirror still cleans up first. All of the marks are
removed with pressure and about 20-30 strokes but as I said the central
region goes first.

I've been using short (1/3) strokes and very little over hang. I've even
tried no overhang and the result do not change.

I've gone through the ATM archives back to the year 2000 and there seems to
be two camps on this subject. Some say this is OK and others say absolutely
not.

Is this normal and should I go on to the finer grits?

Thanks in advance,