How to make black pigment?

How to make black pigment?
The black color are spinel colors except (Cr,Fe)O3.In spinel colours, CoO is essential to give a vivid black colour.Mn contributes to black coloration, but it often causes bubbles to form in the glaze.

The common feature of black spinel chromatics is that their compositions do not contain ZnO.This is also related to the formation of ZnO·Cr2O3 spinel.Black spinel colorings appear very black in lime-barium and leaded frit glazes.

For frit glazes, except for (Co,Ni) O·(Cr,Fe)2O3 spinel solid solution.
When with (Co,Ni)2SiO4 olivine solid solution, it is beneficial to both color and surface properties of glaze.

Co-ni-cr-fe-si is a type of black spinel. The Si, also known as SiO2, is the component of olivine type solid solution, rather than the solid solution in spinel structure.

Cobalt oxide is usually an essential ingredient in black colorings. Without the addition of cobalt oxide, it is difficult to obtain a pure black tone. In recent years on the market without cobalt black material, in fact, it is difficult to get pure black tone glaze. Some rare earth compounds have developed cobalt-free black materials, which are said to produce pure black tones, but their production costs are about the same as cobalt black.