Production of Synthetic Iron Oxide Pigments

The methods used to create natural iron oxide pigments are all "dry" methods. Natural pigment processing steps are primarily concerned with producing the desired physical properties in dry solids, with no involvement of chemical solutions. The term "dry" is used in this context to include calcination, which is also used to produce synthetic oxides from dry chemicals.
The majority of synthetic oxides, however, are produced primarily by manipulating chemical solutions, suspensions, or slurries; thus, the term "wet process" can refer to synthetic oxides produced in this manner. When considering synthetic oxides, keep in mind that their color is determined by the oxide formed, regardless of the process or sequence of steps used: Hematite, or ferric oxide, is red; goethite, or hydrated ferric oxide, is yellow; and magnetite, Fe3O4, is black.