Yes an electron microscope!
However as I have said, it is my contention that it is not individual
particle sizeof the pigment that matters. It is the degree of
dispersion that is important.
Having found my Hegman Gauge I carried out some tests on a few matrials
I had at hand:-
OIL BASED
MATERIAL HEGMAN READING
Vanson Black Litho Ink 20 microns
Winsor & Newton's Titanium White 50 microns
Winsor & Newton's Cadmium Orange 15 microns
Winsor & Newton's Phthalocyanine Blue 45 microns
WATER BASED
Winsor & Newton's Zinc White 50 microns
Winsor & Newton's Poster Colour Burnt Sienna 45 microns
Winsor & Newton's Poster Colour Permanant Orange 30 microns
Winsor & Newton's Poster Colour Lamp Black <10 microns
The oil based materials were diluted with linseed oil, the water based
materials with 25% gum arabic soln.
It would seem that the degree of pigment dispersion of certain artists'
colourants leaves much to be desired!
When one would expect a good quality gloss paint to have a Hegman
reading of < 5 microns,You can see what I'm getting at!
And when one considers that the resolution of a bichromated colloid
system is theoretically 4x that of silver halide, those Gummists (as
Terry calls them) who wish for maximum sharpness etc, in their prints,
should look to the dispersion of their pigments.
Alex.
Alex Nanson
Gloucester UK