Radiography involves the use of high energy Gamma or X-Ray radiation to produce a latent image on a piece of photographic film.
The material’s thickness and density changes are indicated as lighter or darker areas on the film. This allows for the interpretation of the material’s internal features and soundness. X-ray machines or radioactive isotopes are used as a source of radiation. Cracks on a weld sample are noted on a radiograph as a thin, dark and irregular line along the length of the weld bead.