This technique, which revolutionized medicine, was almost immediately used with great profit also for the investigation of paintings. It has proved to be very useful for analysing all types of works of art in a non-invasive way: paintings, ceramic, metal or stone artefacts, both for conservation purposes and for historical-artistic insights.
In particular, radiography can provide useful information on the technique used by a given author, revealing the “internal” characteristics of his artefacts, as well as highlighting any conservation problems, elements that are also useful for his evaluation.
In the case of paintings, for example, the radiographic examination provides a reading of the work in its entirety, returning important indications both on the support and on the pictorial layers, useful for the interpretation of the stratigraphic succession of the original or restored portions. The radiographic image allows, moreover, to reveal underlying paintings, to highlight existing fractures, stucco work, wooden integrations, metal nails, elements of connection of the boards, such as dowels or pins, “incamottatura” canvas or tow in the connections, damage due to attacks by insects, gaps in the pictorial layer and additions, obtaining an initial characterization and mapping of the materials used by the artist and in the course of previous restorations
A BIT OF HISTORY
X-rays entered the artistic and archaeological field practically as soon as W. Röntgen discovered and used them in 1896. In fact, shortly after its discovery, the German scientist attempted to x-ray a painting, but it was only during the First World War that the first X-rays plate of a painting on wood was produced.
Immediately after the first experiments it was understood how useful the applications of X-rays to paintings were: in fact, it was possible to determine the structure of the support, make an approximate analysis of the pigments, as well as search for signatures and unmask forgeries.
Although Röntgen had declared that he did not want to patent and that his invention belonged to humanity, in 1915 Alexander Faber obtained a patent for radiographic techniques on paintings, which effectively led to a suspension of several years of the use of this technique in Germany.
Meanwhile in Tour, a group of technicians, doctors and nurses from the 1914-18 war took the initiative to use a portable instrument on board an ambulance to carry out “home” investigations of works of art.
And in one of the first exhibitions on scientific analyses carried out on works of art, organized in Paris, at the Orangerie, entitled “Scientific techniques in the study and conservation of paintings”, the results obtained with X-rays were exhibited above all .
 M. Hours, La vie mystérieuse des chefs-d’oeuvre : La science au service de l’art
 J.Patfield, D. Sauders, J.Cupitt, Anderson,”Improvements in the acquisition and processing of the X-rays images of Paintings”, NG Techincal Bulletin n.23
There are several techniques for detecting X-rays. The classic method uses a special film, which has to be developed in a laboratory.
In the case of digital radiography, the image is acquired in numerical form and therefore immediately available for any computer processing. Digital radiography can be obtained from chassis with “memory phosphor” scintillator screens. These screens are typically the same size as conventional standard film.