. . . . "It may also be a plastic film, paper or metal, including but not limited to polyester film, paper or spun bonded polyolefins. [0026] In a desirable embodiment of the invention is a solution or dispersion of an ink formulation suitably an aqueous ink formulation most suitably one, which comprises an acrylate polymer. [0027] A process of using a device of the present invention for monitoring sterili" . .