Solvent removable penetrant is the most common application. Evaluation is made with white ambient light.
Water washable penetrant is a rapid and effective means of inspecting large areas or in locations where the solvent would have an injurious effect upon the material or personnel. The inspection is usually made with white light.
Fluorescent penetrant removable both by solvent or water and with evaluation made under ultraviolet light is the most sensitive of the penetrant methods for inspection. A darkened environment is necessary for inspection under the black light.