How can mottling caused by diffraction be reduced when radiographing large-grained metallic specimens?

Mottling caused by diffraction occurs in radiographic imaging when large grains in the specimen scatter the incoming radiation in various directions, leading to a grainy or mottled appearance on the radiograph. By using lead foil screens and raising the kilovoltage, this effect can be minimized.

Using lead foil screens helps to absorb scattered radiation, thus reducing the amount of scatter that reaches the film or digital detector. This results in a clearer image with less mottled appearance. The addition of raising the kilovoltage further enhances the penetration ability of the X-rays. Higher kilovoltage produces higher energy X-rays, which are less likely to be scattered by the large grains, leading to improved image quality.

The combination of these two actions—using lead foil screens and increasing the kilovoltage—produces a more consistent and cleaner radiographic image, effectively reducing the impact of diffraction and mottling associated with large-grained metallic specimens.