Luminescent control

The luminescent method of control  according to the technology of preparing the part, applying penetrating and developing liquids does not differ from the color method. The final operation is to inspect the surface of the part with illumination by invisible ultraviolet rays. The method is more effective, but is used less frequently due to the need for special devices. 

The luminescent method of control  is more sensitive, but requires the use of special irradiation with ultraviolet light and a darkened room to inspect the product. With the luminescent method of control, the defect is filled with an indicator liquid, which is a solution or suspension of a phosphor in a mixture of organic solvents, kerosene, oils, and a surfactant. During development, the phosphor extracted from the defect gives a contrasting trace on a dark background, glowing under the action of ultraviolet rays, which makes it possible to detect defects with an opening of more than 0 1 μm. Due to the increased sensitivity of the human eye in the yellow-green region, phosphors with the maximum light output in this region of the spectrum are used.