Theoretic background Compared to the magnetic particle inspection, the penetrant method differs in the way that defects as cracks or pores etc. can be proven also on non-magnetizable materials. The principle of penetrant testing is based on the fact that a penetrant does not only want to spread optimally on a surface, but also penetrates every defect of a surface, due to its specific characteristics.

If exceeding penetrant is removed from the surface, the penetrant in the material can be made visible by applying a developer.
The penetrant procedure can be applied with daylight-visible fluids (colour contrast penetrant testing) or with fluorescent penetrant, visible under UV-light.

Numerous applications
With penetrant testing, surface discontinuities on all iron metals and non-iron metals, many plastic materials, ceramic materials, glass etc. can be detected fast and without bigger expenditures of parts and machines. Prerequisite for this testing procedure is, that the defect is open to the surface. Penetrant testing is mainly used for the testing of welding seams, cast iron, in shipbuilding, automobile construction, apparatus- and container manufacturing.