What might cause mottling in a radiograph of a steel weldment?

Mottling in a radiograph of a steel weldment can be attributed to various factors affecting the exposure and development of the radiographic film. One significant cause is the failure to use a lead screen during exposure. Lead screens are employed to enhance the image quality of the radiograph by reducing the amount of scattered radiation that reaches the film. When these screens are not used, scattered radiation can lead to non-uniform exposure on the film, which manifests as mottling or uneven density in the resulting image.

Using a lead screen helps to produce a clearer and more consistent image by allowing more of the primary radiation to reach the film while minimizing the effects of scatter. Consequently, when the lead screen is omitted, the radiograph may display mottled patterns due to this lack of control over the exposure conditions.

While factors such as excessive exposure time, the quality of the weld, and improper film processing can affect radiographic images, they do not specifically cause mottling in the same way that the absence of a lead screen does. Excessive exposure time typically results in overexposure rather than mottling, and issues with the weld quality would show up as flaws or discontinuities rather than mottling. Improper film processing affects image clarity and sharpness but does