A detailed study on the dependence of the dispersed phase size versus the concentration of interfacial modifier is undertaken for an immiscible blend system, polyamide/polyolefin modified with a polyethylene copolymer ionomer. The resulting curve is known as an emulsification curve, and evidence is presented which indicates that the point of interfacial saturation of an interfacial modifier on the dispersed phase can be estimated from these data. The characteristic shape of the emulsification curve displays an initial rapid drop in phase size, as would be expected for a system experiencing a drop in interfacial tension. A critical concentration value of interfacial modifier (C(crit)) is subsequently observed, beyond which a quasiequilibrium particle size is obtained. The C(crit) value is directly related to the interfacial area of the dispersed phase and a lower equilibrium dispersed particle size results in a corresponding shift in C(crit) for similar systems. The area occupied per molecule, calculated using the C(crit) value and assuming, as an extreme limit, that all modifier is at the interface, is 5 nm2 per molecule. The area value is in the appropriate range expected for a system with a saturated interface.