Abstract: A method for temporarily marking a surface whose distance from a light beam source can substantially vary, without requiring focusing or refocusing of the light beam, commences with the step of coating a portion of the surface with a light reactant, color-forming chemical solution. The solution is soluble in a liquid solvent that is nonreactive with the surface. The coated portion of the surface is exposed to a collimated, non-focused laser beam exhibiting an airy disk pattern having central bright spot, the exposure occurring for a period of time that enables the central bright spot to expose the coating and to manifest a color change at points of incidence. The bright spot exhibits a diameter that does not exceed a predetermined diameter within an expected distance variations between the source of the laser beam and the surface.