Radiographic testing (RT) is a material testing technique that involves the use of either gamma rays (radioactive isotopes Ir-192 and Se-75) or x-rays.
Radiographic tests have been widely applied when checking for internal defects and the general homogeneity of the material.
When the rays penetrate the metal they are absorbed, i.e. become weaker.
This weakening is less if the rays encounter defects or non-homogeneity, i.e. they are less absorbed then. Gamma and x- rays leave a trace on film emulsion (industrial foil), on which the radiographic examination of internal material defects is based.
