I tucked the bowl of wet Carolina earth into a warm oven for a good overnight drying. You see, after all the mulling of that earth, the texture still felt too gritty. So out I went on the deck with mortar and pestle in an attempt to reach a finer grind. A couple of hours later, I set up my tools with the intent of making paint.
After mulling a bit of earth and adding gum arabic, I arrived at a texture close to that reached with Natural Pigments earth, but still a bit gritty. I decided to stop mulling and fall back to another round with the mortar and pestle. It was my first time with this tool and I did spend an hour chatting on the phone with dear friends while working away. I might have missed some good grinding in all the talk and laughter. :-)
Here is a little comparison of Carolina on the left and last night's Italian Yellow Earth on the right. It's difficult to see here but there are larger grits mixed in with the Carolina paint.
I think that mortar and pestle work is useful, and probably necessary, prior to mulling. This is based on my understanding that mulling separates particles clumped together but does not reduce individual particle size--mortar and pestle reduce particle size. I am coming to appreciate whatever mechanical means pigment manufacturers use to produce such wonderfully powdered material. :-)