LPT/PT is one of the oldest methods applied to locate discontinuities that are open to the surface (surface-breaking defects) due to capillary action.  Used on ferrous, nonferrous and even non-metallic, LPT/PT is remarkable and simplicity in revealing surface imperfections on large and complex material shapes.

The liquid is drawn into defective areas in the material’s surface through capillary action and then draws out to reveal itself to detection using UV lights or other methods, depending on the type of penetrant and dye colouring used.