Abstract: A flame retardant formulation for application as an aqueous working dispersion onto surfaces of normally combustible materials. Upon exposure to elevated temperatures and/or flame, the formulation creates a substantially continuous protective film as it undergoes a transition of composition, with the protective film generally encapsulating and/or enveloping the surface of the article onto which it is applied. In addition to being insulative, the film excludes oxygen from the surface of the substrate, and is capable of radiating infrared and visible light when exposed to elevated temperatures. In the formulation, and upon exposure to elevated temperatures and/or flame, the material releases forms of chlorine, bromine, and phosphorus, for the protection that these materials provide. In addition, antimony oxide is present for its protective property, together with hydrated alumina for its water-release capability.