Neutron radiography is a type of nondestructive imaging similar to X-radiography whereby neutrons are used to create an image. While the earliest examples of this technique appeared in the late 1930s, it was not until the 1950s that it began to see routine applications, typically for industrial inspections and structural quality assurance testing for metals manufacturing. More recently, the use of neutron radiography has broadened to include applications in the nondestructive imaging of objects in art and archaeology. For such applications, neutron radiography is used to reveal internal features or structures of objects, as well as to provide some information on the object’s composition. Some examples of this include the assessment of forming techniques in ceramic vessels to see internal features of cast metals or corrosion products, to assess the stability of an object, or to determine the presence of hydrogenous materials such as water, wood, plants, wax, oil, leather, textiles, paper, or resin. This technique has been of significant value to those researching cultural heritage as it offers a nondestructive method for gaining a glimpse into the life history of the object.
The process of capturing a neutron radiograph requires the use of a neutron source, typically a nuclear reactor. A high intensity beam of neutrons collimated from the core of the reactor passes through the object being analyzed. After passing through the object, the neutrons are recorded either directly onto a piece of X-ray film and then processed in a dark room; or, they are digitally captured using some combination of a digital detector array and a scintillation material that converts neutrons into visible light. The image produced is visually similar to that of an X-ray, yet different in that the neutrons readily pass through elements of higher atomic mass, such as lead and iron, but are absorbed or scattered by hydrogenous materials such as water, wax, oil, and plastic. In many cases, this type of imaging is used as a complementary technique to X-radiography as both images combined offer a unique view of the internal structures of objects.
For this study, neutron radiography was used to capture an image of Rodchenko’s Untitled. We chose to perform it on this piece as it was painted on a wooden (spruce) board, and we hoped to discern the chemical nature of the pigments and shellacs used. This was performed at the McMaster Nuclear Reactor, one of the few facilities in North America where neutron radiographic imaging is available. See the essay “Imaging Using X-rays and Neutrons” in this volume for images of neutron radiographs.