The problem of settlement is a matter how to prevent pigment particles from re-aggregation after all. Theoretically speaking, because of high polarity of surface, inorganic pigments or fillers are easier to disperse. However, as a matter of fact, inorganic pigments are much easier to re-aggregate and settle if improper dispersant used, comparing with organic pigments. The following two aspects have to be considered in order to obtain coatings with minimum settling tendency of inorganic pigments.
Firstly, to select appropriate dispersant -- the selected dispersant must be able to adsorb firmly on surface of inorganic pigments when grinding, to get rid of free energy of newly formed surface arising from particles breaking down, to block re-aggregation of inorganic pigments. After grinding, expansion chain of dispersant should be able to form a thick enough protection layer around particles of inorganic pigments to block attraction among particles due to Van der Waals forces.
To add appropriate anti-settling agent or thickening agent if necessary -- If settling problem is the most serious one in coating system, anti-settling agent or thickening agent could be one of choices. These products reduce tendency of settlement by increasing thixotropy to make pigment suspending in media.