by Miriam
What are x-radiography and infrared reflectography?
Objects can be examined minutely via the thread count of their surfaces and the fronts, backs and edges of their supports. These can be examined under magnification and different sources of light: raking and spectral light, ultraviolet radiation, infrared reflectography and x-radiography. Imaging techniques can be used in the preservation of objects of cultural heritage. The study of the use of these techniques on objects is becoming more and more crucial, providing countless advantages to the use of digital cameras. These images help by highlighting any weak or poorly restored areas in an object. Through the use of this information, conservators can document and make invisible conservation repairs, allowing for the object to stabilize and be on display for the public.
X-radiography and infrared reflectography are examples of imaging techniques used in conservation. X-radiography uses x-radiation to capture images, which can then be linked together into a cohesive whole. X-rays penetrate everything, so they function to detect the distribution of density and radiopacity. In the same way as a medical x-ray, x-rays can record information through to the bottom support layers and the base of a painting.
Developed in the 1960s by Dutch physicist J. R. J. van Asperen De Boer, infrared reflectography is another technique that looks through the underlying layers from the surface. Infrared reflectography beams infrared light onto the surface of an image. Infrared light is only absorbed by carbon-containing substances, such as charcoal or graphite and can distinguish carbon- or graphite-containing pigments. Infrared can penetrate and reflect most other substances, while it bounces off and back to the digital camera with white surfaces, such as lead white paint. An infrared reflectogram, or a digital photograph of this process, is produced for the section of the object that is being tested. If an entire canvas is tested with infrared reflectography, a grid pattern forms in the background of images, due to each individual capture produced.
How can x-radiography and infrared reflectography be used?
X-radiography and infrared reflectography are non-intrusive technologies that can be used to obtain a more detailed account of various cultural objects. While these cultural heritage objects are exposed to
radiation, the levels are so minimal that the items are not harmed in any way. X-radiography can be used on paintings, sculptures and other 3D objects, textiles and archeological materials. As infrared reflectography can be slightly warm, it is important to proceed with caution with paper or textiles; however, this imaging technique can be used on almost all objects. Through the use of one or both of these two technologies, an expansive variety of cultural objects can be studied in depth without leaving a mark. In the case of an x-rayed painted object, lead white and vermillion will stand out, as lead and mercury are incredibly dense. White, gold and vermillion paints will also appear more solidly on the image because they are all radiopaque,
while carbon-based paints are more transparent. The x-rays emitted can thus detect a wide range of densities in an object. Having a stronger emission source achieves more accurate results for a painting on a thicker canvas.These imaging techniques can be used to tell a conservator more about an artifact or a work of art.
Why are x-radiography and infrared reflectography important?
While there are a number of cultural objects that can be studied with x-radiography and infrared reflectography, we will focus on paintings, although similar results and conclusions could be drawn from the study of any other cultural heritage medium. X-radiography and infrared reflectography can reveal compositional changes, the density of paint layers and details of the support itself. All of these elements become apparent once it is possible to see through the entire structure; inscriptions and underdrawings or pentimenti can now be viewed and analyzed. These assist in understanding the artist’s creative process or detecting forgeries and clarifying issues of connoisseurship or attribution.
One famous example is Pablo Picasso’s ‘The Old Guitarist,’ ca. 1903-1904. In this famous painting from the artist’s Blue Period, Picasso decided to reuse one of his older canvases. After testing with x-radiography, an older woman, a young mother nursing her child and the head of an animal became visible on film. The x-rays were able to pass through the thinner and more transparent outer layer, to reach the more absorbent layers beneath. The infrared photograph shows that the mother’s left arm is outstretched and that she appears to be deep in thought. Furthermore, the animal’s head is clearer and appears to be a calf or a sheep to the right of the mother’s arm. Even the underdrawing of the guitar strings done first in pencil come through.
FOR MORE GENERAL INFORMATION CONCERNING X-RADIOGRAPHY AND INFRARED REFLECTOGRAPHY, CONSULT:
Art Institute of Chicago (n.d.). Infrared Reflectography. Retrieved April 24, 2018, from /collections/conservation/revealing-picasso-conservation-project/examination-techniques/infrared.
Art Institute of Chicago (n.d.) X-Radiography. Retrieved April 24, 2018, from /collections/conservation/revealing-picasso-conservation-project/examination-techniques/x-radiography.
Webber, S. L. (2008). Technical Imaging of Paintings, Williamstown Art Conservation Center: Technical Bulletin 5, 1-5. Retrieved from http://www.williamstownart.org/techbulletins/images/WACC%20Imaging%20of%20Paintings.pdf .
FOR FULL BIBLIOGRAPHY VISIT: REFERENCES.
Scientific Analysis & Conservation Tech 