By Francesca Gabrieli

On the 2nd and 3rd of May 2018, the Optical Society of America (OSA) held the Big Data in Cultural Heritage Imaging incubator meeting in Washington, D.C., hosted by John Delaney, National Gallery of Art (USA), Martin Fischer, Duke University (USA), and David Saunders, British Museum (UK).

The OSA is the world’s leading champion for optics and photonics, and the idea of incubator programs is to provide researchers, engineers, and business leaders with the opportunity to meet and discuss the latest advances, challenges, and opportunities in their respective fields.

The Big Data in Cultural Heritage Imaging incubator served as a platform for establishing interdisciplinary collaborations that can help identify improved optical instrumentation and analysis methods to overcome the unique challenges posed by the examination of cultural heritage objects. In the past 20 years, advanced imaging techniques have been applied to the study of art objects, revealing previously unseen aspects of historical artworks and helping conservators and art historians to better understand the composition and history of objects.

The incubator aimed to give an overview of what is state-of-the-art in imaging as applied to cultural heritage, to explore how the use of new technologies available in other fields can improve the quality of art object analysis, and finally to brainstorm about how both conservators’ and scientists’ questions can be answered with these emerging tools.

The incubator consisted of sessions with talks from experts in different fields, round-table discussions, poster sessions, and a visit to the National Gallery of Art (NGA) Scientific Department laboratories. Participants with a variety of different backgrounds came from the US and Europe to share their unique perspectives as conservation scientists, chemists, physicists, and engineers.

The first day of the incubator was focused on macro-scale imaging techniques; the speakers provided a broad overview of the imaging modalities currently available and extensively used for the study of paintings and manuscripts. Elemental imaging (e.g. based on X-ray fluorescence) and molecular imaging (e.g. visible and near-infrared) are powerful tools for the identification and mapping of materials and also for the visualization of sub-surface underdrawings or paintings. This session highlighted the extremely promising technique of X-ray diffraction scanning. Participants from Surface Optics Corporation and the US Army Night Vision & Electronic Sensors Directorate gave an overview of currently available hardware, including reflectance imaging spectroscopy equipment and highlighted the possibilities for collaboration and adapting instrumentation for conservation purposes. Important discussions during the first day of the incubator focused on the ability to manage and interpret the large data sets derived from macro-scale imaging methods. Participants were involved in the discussion about how to combine and register different kinds of imaging information (visible, elemental, molecular), and how to interpret these data sets (using statistical methods such as PCA and algorithms that exploit the spectral information).

Micro-scale mapping techniques were one of the foci of the second day of the incubator. Micro-imaging can be non-invasive (e.g. using micro-scale Raman/micro XRF mapping of small areas of a manuscript) or invasive (analyzing samples removed from the object). Micro-scale imaging techniques that are used widely on cross sections include SEM-EDS, ATR-FTIR imaging, micro-Raman, and micro-fluorescence mapping, which provide much information about the chemical makeup and stratigraphy. The proposal for the future is to combine the data sets such that each imaging modality is registered to the same reference image. Advanced techniques were discussed, such as femtosecond pump-probe imaging and confocal XRF fluorescence. Lattice light sheet microscopy, which is currently used in biology for tracking DNA dynamics, was highlighted and applications in the study of cultural heritage materials were discussed. The use of OCT and NMR for depth profiling was covered, as was ELISA (tagging fluorophores with antibodies), which has been used for the identification and mapping of binders in a material cross-section. The engineers at the incubator indicated their willingness to adapt their systems to better meet cultural heritage field requirements for the study of heterogeneous surfaces.

The final incubator round table discussion was particularly useful in bringing up ideas and comments for future applications and studies:

i) Modern materials, which have been less explored than ancient art, still require an in-depth examination as hundreds of new chemical compounds have been produced in the last century and are widely used by artists;

ii) scientists and conservators are now more interested in the “unexpected” – for example, trace elements, minor components, and degradation compounds formed on surfaces, aspects that should be a focus for future imaging techniques;

iii) the portability of the imaging systems and of the art objects also plays a fundamental role in the choice of technique. It is also important to select the appropriate imaging method carefully, depending on the purpose of the study, and thus a close collaboration with conservators and curators in this field is crucial.

The Big Data in Cultural Heritage Imaging Incubator ended with a behind-the-scenes tour of the National Gallery of Art. Incubator participants and a few OSA staff members were taken into the laboratories of the Department of Scientific Research at the Gallery. Barbara Berrie, head of Scientific Research, showed some of the microscale mapping results of her research using SEM-EDS on a cross section of a painting by Giotto. The tour ended in the macro-scale imaging laboratory where John Delaney, Kate Dooley, and Francesca Gabrieli showed how to collect a reflectance dataset with a visible-to-near-infrared hyperspectral camera (400-1000 nm) on the painting Roulin’s Baby by Van Gogh, painted in 1888.

Thanks to the hosts and the participants, this OSA Incubator was a perfect way to brainstorm about how to improve the quality of the data and instrumentation used in the field of cultural heritage imaging.

For further information visit the website www.osa.org/incubator.

AUTHOR BYLINE

Francesca Gabrieli received her PhD in Chemical Sciences applied to cultural heritage study from the Università Degli Studi di Perugia, Italy, in 2015. She focused her study on the understanding of art materials using vibrational spectroscopies (FTIR, Raman, SERS) portable and non-portable. She is now conducting her postdoctoral research at the National Gallery of Art in Washington DC, USA, with an advanced training fellowship in imaging science. She is using XRF and reflectance imaging spectroscopies for the identification and mapping of art materials, working in close collaboration with conservators and curators.