A method of making a composite barrier coating composition comprising: (a) providing a first aqueous dispersion comprising a dispersed, anionically functionalized matrix resin; (b) providing a second aqueous dispersion comprising a dispersed platy mineral filler; the first and second dispersions optionally including one or more additives selected from the group consisting surfactants, emulsifiers, anti-foaming agents, dispersing agents, wetting agents, leveling agents and thickeners; (c) adding a multi-valent metal cation crosslinking agent to at least one of said first and second aqueous dispersions; and (d) admixing the first and second aqueous dispersions to form the composite wherein the composite forms a stable aqueous emulsion and the multi-valent metal cation is operative to stabilize a film formed from the composite against gas barrier performance loss at elevated levels of relative humidity.