Industrial Radiography or Radiographic Testing (RT) uses ionizing electromagnetic radiation to view objects in a way that can’t be seen otherwise. It is not to be confused with the use of ionizing radiation to change or modify objects; radiography’s purpose is strictly for viewing. It is a method of inspecting materials for hidden flaws by using the capability of short wavelength electromagnetic radiation, x-rays and gamma radiation, to penetrate various materials. Gamma radiation sources, most commonly Iridium-192 and Cobalt-60, are used to inspect a variety of materials. The vast majority of radiography concerns the testing and grading of welds on pressurized piping, pressure vessels, high-capacity storage containers, pipelines, and some structural welds. Other tested materials include concrete (locating rebar or conduit), welder’s test coupons, machined parts, plate metal, or pipewall (locating anomalies due to corrosion or mechanical damage). Theoretically, industrial radiographers could radiograph any solid, flat material (walls, ceilings, floors, square or rectangular containers) or any hollow cylindrical or spherical object.