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Report on Studies on Lead Marking in Radiographic Films and its Prevention
Prolonged contact between radiographic film and metallic intensifying screens often leads to blackened areas in the developed film. The effect is more noticeable the higher the speed of the film and seems to be due to the presence of moisture in the air rather than to the particular metal used as a screen. The use of paper or other organic spacing sheets between the foil and the film was found useless under conditions of high humidity and temperature and quite unnecessary when the film holder is kept moisture free by simple means described herein. X- ray diffraction patterns of commonly used tin coated radiographic foil showed presence of pure lead in the surface but comparative film marking tests showed little difference in the action of pure lead, antimonial lead or tin- coated lead. Comparative intensifying tests under gamma radiation also showed that these three materials had very nearly the same intensifying action. Tests were made using both x- and gamma rays which showed that the use of paper separators between the intensifying screens and films leads to a loss of radiographic sensitivity and definition.
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