A method for determining the degree of mixing between components in a mixing process, the method including the steps of: a) mixing at least two components and at least two luminescent materials to form a mixture, wherein the luminescent materials are added to the mixture separately from each other, and wherein each luminescent material has a uniquely detectable luminescence emission wavelength; b) detecting emitted luminescence from a sample of the mixture, wherein the emitted luminescence includes different luminescence intensities at the uniquely detectable luminescence emission wavelengths of the luminescent materials; c) wherein the ratio of luminescence intensities and/or the absolute or relative intensities of luminescence at the uniquely detectable luminescence emission wavelengths is indicative of the degree of mixing between the components.