MO4431 is a hydrophobic synthetic black iron oxide (magnetite, ferrosoferric oxide) specifically developed for lithographic (offset) inks for check and business form printing.

MO4431 is acicular in shape and has been surface treated to make it organophilic and therefore unwettable by the aqueous fountain solutions used in multigraphic/offset printing. MO4431 complies with the RoHS regulations.