Chemical compounds are stored in plant cells. The colour-producing chemicals are called biochromes. The basics of extracting botanical colours In order to release these chemicals and make them available for ink, we crush and/or cook the plant materials in water to break down the cell walls. Once the chemicals

Tannins are a family of chemical compounds found in plants. Different plants (and different parts of the plant) have different concentrations of tannins. E.g., galls > outer bark > sapwood. When mixed with iron, tannins form new chemical compounds (mostly importantly, ferric-polygalloyl glucose complexes). The chemical compounds are black,