Four manufacturing processes have gained industrial significance worldwide for the production of iron oxide red pigments. The two most important processes for the production of red iron oxide pigments, in terms of volumes, are the Laux process and the Penniman process, which together account for more than 90% of the worldwide demand for synthetic red iron oxides. However, the pigment properties and environmental impact of the two processes differ significantly.
Pigments from the Laux process offer a wide color range with particular strengths in medium and bluish red color shades. The relatively hard consistency of the primary Laux particles has its most positive effect in grades with large particle diameters. Furthermore, the pigment formation via a calcination step leads to good milling stability, particularly in bright reds with particle sizes lower than 0.4 µm.