Grinding pigments and oil separation

[Ramesh Vyaghrapuri]

Hi,

I recently dispersed (didn't really grind as it seemed to be fine powder already) some Red Oxide earth pigment in linseed oil, actually three different kinds of red oxides (from almost yellow ochre in color to indian red in color).

They seemed to require different amounts of oil to grind, which is probably normal as PR101 seems like the more varied of all pigments out there. Anyway, the one that required most oil to grind seems to show oil separation -- each day I find a big blob of oil when I open the tube (it is a mid-sized tube). I used absolutely nothing more than oil & pigment, just to keep it simple.

Anyone with more experience can give me some hints on how to avoid this? I tubed them right after grinding them, maybe I should have waited for a day or two for the paint to setup? Or is this an indication that the paint is not dispersed enough (it seemed alright with a drawdown) or that I am using too much oil (the other pigments used less oil but were of the same consistency when tubed)? Right now, I am just blotting the oil out before using the paint, maybe this separation is harmless..

Thanks in advance.