Abstract: A solution of a hydrophobic substituted, amino triphenyl methane leucocyanide dye in a clear, highly polar solvent free of hydroxyl groups with enough acid added to make the solution slightly acidic which is sensitive to small dosages of ionizing radiation and responds by permanently changing color. Up to one-half of the solution by weight can be replaced by a second solution of an aromatic solvent and an organic fluor. Another modification of the invention is a solution of a leucocyanide dye in a clear polar solvent which has an aromatic group, an organic fluor, and enough acid to make the solution slightly acidic.