Photonics for Cultural Heritage

Frontier, innovative research performed by the “PHOTONICS FOR CULTURAL HERITAGE” group for over twenty years has positioned IESL-FORTH among the leading centers worldwide for scientific research and technological development of cutting-edge laser and optical tools that offer new and efficient approaches to the diagnostics and conservation of works of art and antiquities. Emphasis is placed on: a) laser ablation methodologies for cleaning and restoration, b) laser spectroscopy for compositional analysis, c) multi spectral imaging and d) holographic metrology techniques for structural diagnosis.

The vision and the mission of this activity has been to develop state-of-the-art laser-based methods in order to a) enhance our understanding about CH materials and processes and b) provide versatile and effective tools for the analysis, diagnosis, preservation and restoration of archaeological/historical objects, works of art, and monuments.

The principal axes and the main developmental objectives of the individual activities are highlighted in the following:

Spectral imaging technologies. The main direction of this activity is to develop new methods for the non-contact, non-invasive, in-situ examination and continuous inspection of CH objects. Applications include mapping of varnish and paint layers, visualization of under-drawings, assessment of past conservation treatments, on-line monitoring of cleaning interventions etc., on the basis of reflectance imaging and spectroscopy. The goal of this research is to investigate, quantify and expand the potential applications of spectral imaging on CH objects, while continuous technical developments both in hardware and software target to improve analytical capabilities.

Laser Spectroscopic Analysis. Different spectroscopies, relying largely on laser sources but not ignoring conventional ones, are employed in order to characterize the chemical composition of materials and study photophysical and photochemical processes in condensed phase systems. Emphasis is placed on a) the applications of spectroscopic tools in art and archaeology (LIBS, LIF, Raman, SERS etc) and b) the development of compact/portable laser-based analytical instrumentation for in-situ and field deployable applications.

Laser Interferometry for Structural Diagnostics. The main direction of this activity is to investigate deformation, deterioration and fracture mechanisms in order to evaluate the structural condition of materials and systems. The optical sensing and the 3D recording of almost invisible defects and changes, which allows their location, measurement and exact positioning within the structure of the object as well as their monitoring through environmental and climate changes, conservation treatments, natural or provoked ageing, transportation or handling are among the objectives of this research group. This is achieved by the effective transfer of interferometric techniques and know-how to CH applications (artworks and monuments) and the continuous inspiration, design, development and realization of new experimental processes, methodologies and instruments in order to exploit the full potential of laser metrology.

Cleaning Artworks with Lasers. Research at the Laser Cleaning (LC) group is developing novel laser ablation methodologies in order to meet a number of diverse conservation and cleaning challenges. Highlight of this activity is the development of a prototype laser system and methodology for the removal of pollution encrustation from the Parthenon Sculptures, which ensures safe and controlled cleaning without discoloration side-effects. This methodology is being applied since 2002 in a number of sculptures at the Athenian Acropolis Monuments (i.e. the West Frieze, metopes and pedimental sculptures of the Parthenon, the Frieze of the Athena Nike Temple, and the roof of the Caryatids’ porch in the Erechtheion). Recently it has been also included in the regular conservation practice of the Acropolis Museum and along these lines an advanced laser laboratory has been set up on the visitors’ floor where the Caryatids are exhibited. Removal of pollution accumulations from their surface takes place in this laboratory while visitors can follow live the cleaning process being carried out. Further synergies between the Acropolis Museum and IESL-FORTH have been planned in the context of an “open common laboratory” in which modern laser based diagnostic and imaging techniques will be used for expanding the knowledge and deciding the best conservation practices for the exhibits.

Current research and activities aim at:

• elucidation of laser induced side-effects in Cultural Heritage applications e.g. yellowing of stonework and pigments’ discoloration,
• optimisation of laser assisted removal of polymeric over-layers from paintings,
• monitoring and control of the cleaning intervention through optical and laser based techniques (spectral and non-linear imaging, holographic interferometry, laser spectroscopies etc),
• realization of laser cleaning projects on important CH objects and monuments in the lab or in-situ.

1. V. Tornari, E. Bernikola, K. Hatzigiannakis, K. Melessanaki, P. Pouli, Synchronized Deformation Monitoring in Laser Cleaning: an Application for Cultural Heritage Conservation, Universal Journal of Physics and Application 1, 149, (2013)
2. V. Tornari, E. Bernikola, E. Tsiranidou, K. Hatzigiannakis, M.Andrianakis, V. Detalle, J.L. Bodnar, Micro-mapping of defect structural micro-morphology in the documentation of fresco wallpaintings, International journal of heritage in the digital era, 1 (2), (2013)
3. V. Tornari, A. Moropoulou , Crack micromorphology detection in stone samples by digital holographic speckle pattern interferometry, Built Heritage 2013 – Monitoring Conservation and Management Conference Proceedings, Milan – Italy Editor in chief M. Boriani, edited by R. Gabaglio, D. Gulotta, (2013)
4. V. Tornari, E. Bernikola, P. Bellendorf, C. Bertolin, D. Camuffo, L. Kotova, D. Jacobs, R. Zarnic, V. Rajcic, Surface monitoring measurements of materials on environmental change conditions, SPIE proceedings Vol. 8790, Optics for Arts, Architecture and Archaelogy IV, (2013)
5. M. Oujja, M. Sanz, E. Rebollar, J. F. Marco, M. Castillejo, P. Pouli, S. Kogou, C. Fotakis, Wavelength and pulse duration effects on laser induced changes on raw pigments used in paintings, Spectrochimica Acta A, 102, 7, (2013)
6. K. Hatzigiannakis, E. Bernikola, V. Tornari, A new portable Digital Holographic Speckle Pattern Interferometry system for artworks structural documentation, Lasers in the Conservation of Artworks – LACONA IX proceedings, eds D. Saunders, M. Strlic, C. Korenberg, N. Luxford and K. Birkholzer, Archetype publications Ltd, London, (2013)
7. E. Tsiranidou, E. Bernikola, V. Tornari, T. Fankhauser, M. Läuchli, N. Baschlin, C. Palmbach, Studying transportation effects on canvas paintings by full field digital holographic techniques, Lasers in the Conservation of Artworks – LACONA IX proceedings, eds D. Saunders, M. Strlic, C. Korenberg, N. Luxford and K. Birkholzer, Archetype publications Ltd, London, (2013)
8. S. Kogou, A. Selimis, G. J. Tserevelakis, P. Pouli, G. Filippidis, C. Fotakis, The use of non-linear microscopy techniques to assess the affected region in the laser cleaning of polymeric coatings, Lasers in the Conservation of Artworks – LACONA IX proceedings, eds D. Saunders, M. Strlic, C. Korenberg, N. Luxford and K. Birkholzer, Archetype publications Ltd, London, 103-107, (2013)
9. Zs. Márton, I. Kisapáti, P. Pouli, E. Bernikola, V. Tornari, Laser cleaning of excavated fresco fragments: testing and optimization of laser parameters and structural monitoring by means of Digital Holographic Speckle Pattern Interferometry, Lasers in the Conservation of Artworks – LACONA IX proceedings, eds D. Saunders, M. Strlic, C. Korenberg, N. Luxford and K. Birkholzer, Archetype publications Ltd, London, 59-66, (2013)
10. E. Bernikola, K. Melessanaki, K. Hatzigiannakis, P Pouli and V. Tornari, Real-time monitoring of laser assisted removal of shellac from wooden artefacts using Digital Holographic Speckle Pattern Interferometry, Lasers in the Conservation of Artworks, eds D. Saunders, M. Strlic, C. Korenberg, N. Luxford and K. Birkholzer, Archetype publications Ltd, London, 52-59, (2013)

Foundation for Research and Technology - Hellas, Heraklion, Greece