Penetrant Testing



Penetrant testing consists in applying a coloured or fluorescent penetrant to a previously cleaned surface. The penetrant seeps into emerging defects by capillary action.

After a penetration time of 15 to 20 minutes at room temperature, the excess penetrant is removed by washing. After drying, a white developer is applied to the surface to be tested. The penetrant contained in the possible defects then bleeds out into the developer. Defect images appear immediately or up to 30 minutes after applying the developer. Two (2) procedures are mainly used: water-washable coloured penetrants used in combination with an organic carrier containing a developer, and pre-emulsified fluorescent penetrants used in combination with a dry developer; the latter being the most sensitive.


  • Easy to manually implement on site.
  • Economical.
  • Unaffected by the orientation of the defects with respect to the surface.
  • Possible detection of small defects likely to cause possible leakage of testing automated lines.
  • Can be used on non-ferromagnetic materials for which magnetic particle testing is ineffective.
  • Can be used on ferromagnetic components that are critically demagnetized or that are too geometrically complex.