PISTACHIO: Photonic Imaging Strategies for Technical Art History and Conservation

Our tangible cultural heritage, both historic and contemporary, is made from a plethora of complex multilayer materials. What we see is often only the surface and form of an object. Hidden below are the materials and evidence of the processes by which the objects were originally created. By using state of the art imaging / spectroscopy systems which can map the composition and reveal the stages of their creation, we gain an understanding about the meaning and significance, both in their original context and our present day. This is at the heart of the disciplines of technical art history, archaeology and material culture studies. It also informs collections care, access policies and conservation of cultural heritage.

Infrared imaging and spectroscopy is particularly well suited to looking below the surface, as the scattering which normally occurs with visible light is usually much less. Thus the infrared penetrates further into the object. Depending on the material and its structure the infrared light will be absorbed or reflected. This can either be directly imaged or modulated (Fourier Transform Spectroscopy) to acquire spectroscopic information indicating the chemical composition. Most techniques employed at present within the field of cultural heritage can only make spot measurements; to map large areas would take hours to days to acquire the data and therefore is not usually viable or suitable for in-situ measurements. Other techniques require samples to be taken and are therefore invasive. We aim to explore state of the art IR imaging strategies that will be "fit for the job". This implies wide bandwidth, full field and fast techniques coupled with signal processing/ photonics methods to analyse, visualise and manipulate large multivariate data sets. By exploiting state-of-the-art laser sources developed at Heriot-Watt and providing massively tunable infrared light, we will explore and develop several complementary strategies for 4-dimensional imaging (3 x spatial, 1 x wavelength). Compressive sensing illumination techniques and machine-learning based data processing will allow us to image rapidly and efficiently while also extracting the maximum value from our datasets by automatically classifying surface and sub-surface features.

In this way we expect to produce outcomes of shared value for both the ICT and Technical Art History researchers in our team. Contextual information from art history will inform the photonic design and computational anaylsis strategies we deploy, while powerful ICT-led techniques will provide the Technical Art History community with new technical capabilities that reveal previously hidden structure and history.

The significance to the public of our cultural heritage has motivated us to integrate outreach activity from the start, in particular a dynamic website using 4D data to allow an interactive tool for exploring the chosen case studies, reflecting the People at the Heart of ICT priority.

The project includes industrial partners who will contribute resources and expertise in mid-IR lasers (Chromacity Ltd.) and mid-IR cameras (Thales Optronics Ltd.). Our partners have committed substantial in-kind support in the form of access to their technology and contributions of staff time. Furthermore, their engagement ensures that activities within the project, and the outcomes these generate, can be rapidly evaluated for adjacent commercial opportunities.

EPSRC priorities are reflected in the project's structure. Cross-Disciplinarity is embedded as collaborations within the ICT community (Photonics & AI Technologies researchers) and with researchers from the AHRC-funded Cultural Heritage community. Co-Creation is essential: only by combining the distinct technical, contextual and material resources of each research group in our team will the project succeed in delivering new capabilities for IR imaging and analysis and new insights into culturally important objects of shared value.

Our research will produce immediate academic impacts, with industrial, economic and societal impacts emerging over a longer timescale.

1. Impacts on Project Researchers
Through the training and development of Masters and PhD students in this cross-disciplinary project, the research will support the UK's need for skilled graduates with an awareness of how their subject can influence other disciplines. The named researchers, Dr. Margaret Smith and Dr. Luke Maidment, will also be developed through mentorship by Reid and Young, via the extension of their professional networks across disciplines, connections with industry and access to staff development courses.

2. Impacts on External Researchers
This project anticipates high-impact publications being achieved by developing and applying state-of-the-art photonic technology--enhanced by new computational techniques--to challenging problems encountered by technical art historians. The envisioned ultra-broadband imaging capability will allow the composition of complex heterogeneous cultural heritage to be mapped at speed, opening up new possibilities for studying multi-layer objects and large objects in-situ. This will provide technical art historians and conservators with new insights into the making and meaning of these objects.

We will generate new scientific and engineering knowledge in the areas of mid-infrared imaging and spectroscopy, with the strong likelihood of wider applications in areas as diverse as healthcare, defence, non-destructive testing, metrology and material science. The methods developed will impact directly on scientists and policy makers including:

-Researchers characterising coatings and pigmented paint systems in industry and academia
-Researchers in forensic science, healthcare and defence
-Conservation scientists and collections managers in the Cultural Heritage sector through improved strategies methods of objects analysis and visualisation
-Senior Management policy makers responsible for allocating resources and wealth generation within private and public collections.

3. Impacts on Culture Heritage and Society
New insights about the making, meaning and condition of our cultural heritage will inform our strategies for the display, interpretation and care of such objects now and for future generations. This will also provide us with a better understanding of the techniques originally employed to create various forms of cultural heritage ensuring these skills used are documented before they are entirely lost. These enrich our understanding of the past and how it has influenced our present society.

4. Socio-Economic Impacts
Public institutions are charged with the care and access of cultural heritage for scholarly research, widening participation and public appreciation. This is set against a need for efficiency in resources (e.g. energy, space, transportation) and reduced public funding. By using the data in different ways (interpretation, didactic/interactive displays, preventive conservation measures, web based resources), an informed strategy of collections care and public facing policy which is based on the significance, meaning and requirements of the objects can be achieved. The total contribution of heritage to the UK economy can be estimated at just under £50bn per year (Data: Lottery Heritage Fund, 2016), making our cultural heritage accessible on different platforms is thus of great potential value and essential for further growth.
Our full proposal will contain an engagement plan (see Pathways to Impact) with separate threads targeted at both the general public and at specialists. For example, the thread aimed at the general public will link into existing initiatives and networks within science and arts at HW and Glasgow e.g. Science Festival, Explorathon, IOP, while that directed towards engagement with specialists will pursue potential applications in sectors such as environmental protection and forensics / security.