As we recently discussed, our paintings and objects conservators are currently investigating the&nbs

As we recently discussed, our paintings and objects conservators are currently investigating the materials and techniques used to create our ancient Egyptian portrait panel paintings.While there were a wide number of materials used to create the paints found on the portraits, part of our investigation has focused on the use of indigo. Although indigo has been identified on some ancient Egyptian textiles, such as this Female Personification from the 5th century C.E., its use as a paintis less well studied.The presence of indigo may be preliminarily characterized with imaging techniques and FORS. In the righthand image above (an infrared subtraction image), light-colored areas correspond with the likely presence of indigo.We are currently investigating the limitations and advantages of the non-invasive techniques to which we have access here at the Brooklyn Museum. While the identification of the paints on our portraits is ongoing, we have also been creating boards with known materials to investigate the ways these materials respond when captured with multiband imaging techniques. Infrared imaging is one such technique. By post-processing images on the computer, we can use infrared images to generate both false color and infrared subtraction images which may be helpful when attempting to identify regions of indigo application. Indigo characteristically appears red in falsecolor images (seen in the center of the images below), and has a bright white appearance in the infrared subtraction images (on the right).Infrared subtraction imaging for the characterization of indigo does pose some challenges. Looking above at Portrait of a Noblewoman, while the bright areas of the purple clavus appear to contain indigo, the wooden substrate on which the paint has been applied also has a faint response (note: these images have been heavily manipulated in Photoshop). In Portrait of a Young Person below, the bright beads appear to be pure indigo. Other areas, which appear to contain paint mixtures, are more ambiguous, and our investigation of these regions is currently ongoing.One of the challenges of the infrared subtraction imaging is that it is imaging the response of the indigo under certain lighting conditions, and other materials may have similar responses, such as the wood substrate described above. This complicates our interpretation of the images, and means that further analysis is necessary. FORS can help in this regard, but it also has its limitations, so we are partnering with other museums to perform different types of analysis. The culmination of this work will be presented at an upcoming APPEAR conference in May 2018, at which scientists, conservators, curators and other museum professionals will convene to discuss analysis of their respective ancient Egyptian portrait collections.Posted by Dawn Kriss -- source link

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