I would like to know if 10 grams of pigment is adequate to fill a 50 ml tube, or if 10 grams of pigment typically fills a 20 ml tube, when making oil paint following your instructions.
It is difficult to provide a universal rule of paint volume for all pigments. The volume largely depends upon the individual pigment and, more specifically, on the particle size and shape of the pigment and its specific gravity, as well as the desired viscosity of the paint.
For example, 100 grams of lead white (basic lead carbonate) requires about 12 to 18 grams of raw linseed oil to produce about 30 to 40 ml of paste paint. On the other hand, 100 grams of lamp black (carbon) needs about 100 to 120 grams of oil, making over 100 ml of paint.
The oil absorption rate for each pigment is listed on the product page of each pigment, which you can see by clicking on the pigment title or picture in the Natural Pigments online store.