If the pigment is already finely ground for artist use, you don't really have
to grind them again. You just need a way of dispersing the pigment.
>> I bought my lampblack at an art supply store, so presumably painters mix
this
stuff up regularly. How do they do this?
>>
I have prepared my own burnt sienna paints for brush painting when I studied
for an old Chinese painting master. Basically you use a mortar, put your
pigment in, slowly add in gum and start grinding it. Add more gum gradually
until you reach the consistency that you need. As mentioned above, if the
pigment is already prepared for artist use, I don't think the grinding is
critical. It is the mixing.