Radiogaphic Testing (RT) involves using a source of X-ray or gamma rays. The source sends the rays through the test piece. A film that is sensitive to these rays is placed behind the object. The test piece absorbs part of the radiation. Areas with higher density or thickness absorb more of the rays resulting in an image on the film. The film is developed with chemicals just like regular photography film. After developing, the film is interpreted by a qualified inspector.