Abstract: A method and composition for non-destructive testing of magnetizable workpieces such as steel billets. A dry dispersion of ferromagnetic particles in combination with a fluorescent pigment and a water soluble carrier are deposited on the workpiece which is simultaneously or thereafter magnetized. The magnetizable particles are attracted to surface imperfections by the action of the magnetic field and become clustered therein to form indications. The indications are fixed more firmly to the piece by applying an aqueous spray, consisting either of a water mist or steam which activates the water soluble carrier so that upon drying, the indications remain firmly attached to the workpiece. Subsequent examination of the workpiece under ultraviolet irradiation enables the inspector to determine the extent and the location of the flaws.