American Society for Nondestructive Testing (ASNT) Radiographic Testing Practice Test

Overall film mottling on a radiograph developed from a steel weldment often results from fluctuations in the quality of the radiation reaching the film, which can be significantly influenced by the presence or absence of a lead screen. When a lead screen is employed during exposure, it helps to improve image quality by absorbing scattered radiation and preventing it from reaching the film. This can lead to a more uniform exposure across the film.

If a lead screen is not used during exposure, the film can become subject to scatter radiation, which can cause variations in density across the film. These variations manifest as mottling, leading to a radiographic image that lacks clarity and detail. The random radiation scatter creates a grainy appearance instead of a smooth, uniform film density. This phenomenon emphasizes the importance of using lead screens to control scatter and improve overall image quality in radiographic testing.

In addition to this, other factors like processing temperature, exposure time, and film sensitivity also play significant roles in radiographic quality. While they can contribute to defects on the film, they are less directly linked to the mottling seen specifically due to scatter effects from the absence of a lead screen.