Abstract: A crosslinkable polymeric emulsion has a pH from about 1.5 to about 8.5 and includes a carboxyl-substituted latex polymer dispersed in an aqueous medium, an Iron (III) compound and an amount of a stabilizer, selected from the group consisting of nonionic surfactants and protective colloids, effective to sterically stabilize the emulsion. A method for making a crosslinked polymer film includes forming a layer of the crosslinkable polymer emulsion and drying the layer to form the crosslinked polymer film wherein the film is ionically crosslinked between carboxyl substituent groups of the polymer by Iron (III) cations. A crosslinking agent for carboxyl-substituted polymers includes particles of a water-insoluble Iron (III) compound having an average maximum characteristic linear dimension of less than or equal to about 5 microns.