Copper sulfate reducer is useful for lightening and improving the diagnostic quality of dark radiographs The solution consists of capper sulfate, sodium chloride, and sulfuric acid. The radiograph is immersed and bleached in the solution until it turns white, redeveloped in weak developer, and fixed. Reduction is superproportional; that is, the percentage of reduction is greater in darker areas than it is in lighter areas. The degree of reduction decreases with increases redevelopment time. The reduced radiograph may have a gray, brown, or black image. Resolution is increased on the reduced radiograph.