Abstract: Flaws in the surface of a physical object, such as cracks, breaks, and other physical discontinuities in metal surfaces are detected by inspection under ultraviolet irradiation after the surface has been coated with a novel flaw detection medium comprising an organic liquid solution of particular organic phosphor materials with an organic binder. The soluble organic phosphor materials found useful in this manner exhibit luminescence when excited by ultraviolet irradiation and are selected from the general class of heterocyclic aromatic nitrogen compounds. In the present inspection method, a coating of the flaw detection medium is applied to the surface being inspected and the dried coating then removed except at the flaw sites prior to inspection. The present liquid flaw detection medium can also be prepackaged for convenient dispensing from a pressurized container through use of conventional propellants such as fluorinated hydrocarbons or their equivalent.