Time to put this thread to bed.
The Cal-Graf screen is relative to nothing. No idea what the screen size is or why they selected that particular screen size.
For GOEX, KIK and the defunct Elephant.
2Fg is screened: pass through 16 mesh, stop on 30 mesh.
3Fg is screened: pass through 20 mesh, stop on 50 mesh.
Essentially, When the powder is screened, anything passing through the 50 mesh bottom 3F screen is 4Fg. Were it not for flintlock pan powder almost all of this minus 50 mesh "process tailings" would have to be reworked back into the powder stream at the powder press.
Lets look at 3F using industry standard lab screens.
KIK 3Fg, Lot 00.04 (May 2000 shipment)
Trace on the 20 mesh.
14.4% retained on the 30 mesh screen.
42.6% retained on the 40 mesh screen.
43.0% thru the 40 mesh screen.
(Only a trace through a 50 mesh)
GOEX 3Fg, Date Code 99JY20C
Trace on the 20 mesh.
70.8% retained on the 30 mesh screen.
26.2% retained on the 40 mesh screen.
3.0% thru the 40 mesh.
(Only a trace through a 50 mesh.)
Elephant 3Fg, Date Code 22/00
Trace on the 20 mesh.
58.7% retained on the 30 mesh screen.
35.1% retained on the 40 mesh screen.
6.2% thru the 40 mesh.
(Only a trace through a 50 mesh.)
What is sold as 4Fg is usually process tailings. That is any corning mill product passing through the smallest screen in the 3Fg range, i.e., 50 mesh. What cannot be packaged as 4Fg would normally be reworked into the product stream.