This method is used to reveal surface breaking defects by the bleed out of a coloured or fluorescent dye.
The technique is based on the ability of a liquid to be drawn into a surface breaking defect by capillary action. This method is a generally low cost solution which is applicable on most solid materials and can be used for the inspection of newly fabricated products as well as on in-service components. Dye penetrant inspection may be
applied under day light conditions using a red contrast dye for regular sensitivity flaw detection. When a high detection sensitivity is required the fluorescent method may be used under appropriate light conditions.