Q: I want to make my own paints from dirt, rocks, vegetables, spices, etc. I have seen paint make from colored dirt by adding a little white glue and some water. Is this going to work with everything?
A: The problem with most vegetable-based colors is that they are fugitive—this means that with exposure to light, the colors will fade more or less quickly. If this doesn’t matter to you, you have a wide range of choices. Saffron makes yellow, as does turmeric; Carrot juice makes orange; spinach juice makes green; pomegranate makes pink, blackberries make purple; etc. The addition of glue or starch will make a thicker paint, which will have less tendency to separate when applied to paper. (Remember the chromatography experiments from High School biology?)
If you want a more permanent paint, your palette of colors will be more limited. The colors of “dirt” or clay are (largely) due to the presence of mineral oxides, such as iron, which yield the permanent “earth tone” colors which range from yellow ochre to rusty red, brown, and black. A permanent (carbon) black can also be made from charcoal. Finer grinding of the pigmented material makes better paint, and it is further improved by adding glue.
For more exotic permanent colors, you have to find appropriately colored rocks and minerals, and grind them to a fine powder. You can do this with the use of a jaw-crusher and a hammer-mill; but it might be more work and equipment than you want to get into, and some of these minerals (especially the lead and uranium oxides and cinnabar, which contains mercury) are toxic. In the old days, painters got their apprentices to do the grinding of pigments, which were then mixed with various drying oils, which are oils that form a durable film upon exposure. Linseed was predominant among them even then, but walnut oil and poppyseed oil were also used.
Alternatively, you can try using egg yolk as a painting medium, instead of oil. This is a traditional technique. The idea is to carefully remove all traces of white by holding the separated yolk in a paper towel, then puncture it and use what drips out, discarding the skin of the yolk. You then mix this with paste-consistency solutions of pigment and distilled water and use it. This will work best with the earth pigments—I’m not sure about the spices.
For more information about mixing paint from scratch, try the classic and still-useful resource: Ralph Mayer, The Artist’s Handbook of Materials and Techniques (1970), Viking Press, New York NY, SBN 670-13665-4.