Sand paper

[DutchGramps]

I got some waterproof aluminium oxide paper from an outlet marked "P400 No. 600"; no brand name but the quality is excellent.
Question: what's the grit size: 400 or 600?  The seller had a real dumb expression when I asked him, and Google had no solution for this burning problem...

[Ben I. Voss]

If I remember right, I think the grit size is proceeded by the letter "P". Maybe?  Try comparing it to known grit sizes of similar paper.

[David Veith]

If I remember right One is working off a Europe system and the other is America. The 400 is American
David Veith

[D. Taylor Sapergia]

The thing to do is use it to polish a piece of metal, having gone through the coarser stages first of course.  There's a considerable difference between the finish left by each of those two grits, and you should see a difference.

[FL-Flintlock]

There are many different grading systems for abrasives such as:
CAMI - Coated Abrasives manufacturer’s Institute
FEPA - Federation of European Producers Association
"0" or "ought" grade system.
JIS system used in Japan.

Of course I can't get the forum software to play nicely with my graphics so I've sent you an email.  If anyone else would like the grit charts, just drop me an email:
mark@fire-iron.biz