The properties of the I.R. radiation can also be used to improve examination of paintings on canvas in transmitted light. In fact, with respect to I.R. techniques the complete absence of a reflection on the surface of the outermost layers improves the possibility of seeing preparatory drawings or pentimentos. In the I.R. reflected techniques the external layers have to be passed through twice: the first time the radiation has to reach the inner most layer, be partially reflected, and then pass through the layers to reach the outer one. When transillumination is used, the radiation has to pass through the canvas and the preparation, but it will pass through the paint layer only once. The transmitted I.R. can be used to integrate data obtained with the x-ray radiography for paintings with a low radiopacity and with ground preparations with white lead, or even in those cases where a preparatory drawing made with ivory black or carbon black can not be seen under radiographic techniques.