Ink jet printer ink composition comprising a dispersion of pigment in a diluent and wherein the maximum volume packing fraction of the disperse phase is not greater than 0.25 at 30 DEG C. Where other solids are present in the disperse phase in addition to the pigment, the value for maximum volume packing fraction applies to the total solids content of the disperse phase. Where the pigment is the only component of the disperse phase, the disperse phase should form more than 7 % but not more than 25 % by weight of the ink. Where the ink includes a component which is dissolved in the diluent, the maximum volume packing fraction of the components of the composition other than the diluent should not exceed 0.45.
