This summary was provided by Sagita Mirjam Sunara. Sagita is based in Croatia, she traveled to London for this conference and has provided me with a summary of three of the afternoon lectures.
Visible-Induced Luminescence Imaging Applied to Ancient Stone Sculpture
Giovanni Verri (The British Museum, Department of Conservation and Scientific Research)
Just like wall paintings and ceramics, ancient sculptures and architecture were frequently painted. In most cases, original coloration has been lost due to weathering, unfavorable microclimatic conditions, and un-sympathetic cleaning procedures. Scientific investigation and imaging technologies can reveal the presence of color on ancient objects, thus opening new insights in the understanding of ancient art.
Giovanni Verri presented one of the techniques that can be applied for characterization of materials in archaeological museum objects: visible-induced luminescence imaging in the near infrared range (800-1700 nm). This is a non-invasive, low-tech imaging technique, very similar to UV induced luminescence imaging, which is often used by conservators and conservation scientists. Verri and his team used this technique for identification of Egyptian blue in several objects in the collection of the British Museum. When irradiated with visible light, Egyptian blue emits infrared radiation. Furthermore, Egyptian blue is highest IR emitter at a molecular level and an extremely long half-life. Visible-induced luminescence imaging allowed detection of single particles of this pigment on examined objects, even when they were covered by layers of discolored binding media, varnishes and inorganic patina.
This technique can provide information on distribution of blue material with respect of the construction of the object. It is useful to inform sampling strategies, and may help in authentication of objects and in the identification of appropriate conservation treatments.
Multispectral Image-Based Paint Formulation Software for Restorative Inpainting
Marissa I. Haddock, Roy S. Berns (Munsell Color Science Laboratory, Center for Imaging Science, Rochester Institute of Technology)

Marissa Haddock developed a computer program that provides a color match and paint recipe for restorative inpainting. She took a technique traditionally used in industrial paint and plastics formulation and applied it to art conservation. Her research focuses on characterizing and developing a spectral database of the optical properties of the Gamblin Conservation Colors, designing and creating an application color matching software tailored to the needs and practices of art conservators and investigating the use of multispectral imaging as an additional measurement tool for color matching formulation.
Perceived color is a function of the object, the light and of the observer. Mixing paint for retouching requires good knowledge of pigments and color matching. However, if one of the above-mentioned factors changes, the color changes too. Computational techniques can be used to create a color mixture that will match the original paint under a range of viewing and illumination conditions. Multispectral Image-Based Paint Formulation Software performs both image-based color matching, and color matching based on direct spectrophotometric measurements. After taking the image data or contact measurement, paint formula is devised. Pigments that most closely match the mixture are selected, and their concentration in the mixture calculated.
Non-Invasive Color Restoration of Faded Paintings Using Light From a Digital Projector - the topic of an article in the Wall Street Journal
S. Cuellar (Straus Center for Conservation and Technical Studies, Harvard Art Museum; MIT Media Lab), J. Stenger (Straus Center for Conservation and Technical Studies, Harvard Art Museum; Center for the Technical Study of Modern Art, Harvard Art Museum), R. Gschwind (Imaging and Media Lab, University of Basel), A. Mohan (MIT Media Lab), Y. Mukaigawa (MIT Media Lab; Institute of Scientific and Industrial Research, Osaka University), R. Ruskar (MIT Media Lab), K. Eremin (Straus Center for Conservation and Technical Studies), N. Khandekar (Straus Center for Conservation and Technical Studies)

Jens Stenger of Harvard Art Museum gave a presentation of a conservation treatment that does not change the paint surface physically.
In 1963 Mark Rothko donated five paintings on canvas to Harvard University. These paintings are today known as Harvard Murals. Due to the fugitive nature of the pigment he used (Lithol Red) and overexposure to light, paintings had faded greatly and were taken down in 1979. They have been in storage ever since.
In order to establish the original appearance of the paintings, Ektachrome photographs of the paintings were consulted. The photographs had faded as well, and had to be restored. Once the original appearance of the paintings was known, it was necessary to decide how the original color can be brought back. Since inpainting would be unacceptable, alternative methods were examined.
The concept of bringing back the color by using colored light and illumination was first formulated in a paper by Raymond H. Lafontaine “Seeing Through a Yellow Varnish: A Compensating Illumination System” (1986). Lafontaine used a combination of neutral light and blue light to ‘look through’ the yellowed varnish, and two slide projectors to ‘restore’ the original color of the painting. The same concept was used for Rothko’s paintings. An image of the current state of the painting was taken and compared with the target image in the computer. A compensation image was created and projected on the painting, recreating its original color. Ambient light had to be adjusted. As Rothko’s paintings are still sensitive to light, light levels have to be adjusted to a safe level.
Thanks to Sagita and Carrie for your summaries of this exciting and interesting conference. I hope you both had a lovely time and a nice cup of tea.
