Spinning disc processing (SDP) has been utilized to modify the aqueous, inverse co-precipitation method for the production of Fe3O4 nanomaterials patented by Massart in 1982 [1]. Size distributions within the 3 to 12 nm range have been produced, with narrow particle size spread, on a rapid, continuous basis. It has been demonstrated that this processing technique results in a general reduction in particle size. Further, the role and limits of applicability of tartaric acid as a surfactant for particle formation control have been established to lie within the range of 1:1 to 10:1, [tartaric] to [Fe], with concentrations in excess resulting in amorphous materials and below this having minimal effect. Marginal, high concentrations have been demonstrated to occasionally result in particles with induced twinning and lattice dislocation defects.