A microcapsule toner containing trimellitic anhydride for use as a foam inhibitor in printing applications was synthesized by liquid-phase separation in organic solvents. It is possible to determine materials appropriate for the microencapsulation of trimellitic anhydride from solubility parameters calculated on the basis of the molecular structures of raw material candidates. Considering solubility parameters of various polymers, the polyethylene/ methacrylic acid copolymer was selected for the microcapsule wall material. In addition, two kinds of solvents, toluene [solvent (a)] and isoparaffin [solvent (b)], were employed. It was necessary for the microcapsule materials to meet the following conditions: (1) the wall material must completely dissolve in solvent (a); (2) the core material must disperse well, but not dissolve in solvent (a); and (3) the wall and core materials must not dissolve in solvent (b). By using mixtures of either lecithin and basic barium petronate or lecithin and basic calcium petronate as charge control agents, the trimellitic anhydride microcapsules could be charged either positively and negatively, respectively. The microcapsule toner fabricated in this method was successfully applied in commercial printing machines, where it inhibited foaming effectively enough to satisfy product requirements in the printing industry. (C) 2003 Wiley Periodicals, Inc.