or transmitted light. Transillumination consists in lighting the painting from the back and observing from the front the behaviour of the rays that pass through the layers. In this examination, the presence of any details under the visible surface can be identified. In a very simple way, recourse to other types of examinations can often be avoided. Examinations do not necessarily give more precise or better information just because they entail more sophisticated methods. This type of examination is also useful in identifying those situations when the support or the ground preparation do not permit the transmission of luminous rays; just as the use of infrared and x-rays may be indispensable for obtaining different and specific types of information.