Tiphaine Bardon

This project explores the scope of the cutting-edge terahertz time-domain spectroscopy and imaging as a potentially non-invasive diagnostic and imaging tool for the study of archival document

Thesis title: Terahertz time-domain spectroscopy and imaging of archival documents

Primary supervisor: Prof. Matija Strlič
Secondary supervisor: Sir Michael Pepper
Starting date: September 2011
Projected completion date: May 2016

This project explores the scope of the cutting-edge terahertz time-domain (THz-TD) spectroscopy and imaging as a potentially non-invasive diagnostic and imaging tool for the study of archival documents. While some previous research successfully uncovered drawings or texts from inaccessible layers in heritage artefacts using THz-TD imaging, inscriptions in some historical documents investigated in this project could not be revealed with this technology. This work therefore explores the parameters influencing contrast in terahertz images of historical documents, in order to objectively inform curators when terahertz technologies are likely to give well-contrasted images of inscriptions in a complex archival document and are a useful non-invasive alternative to current digitization processes. These parameters include the dispersive refractive indices and absorption coefficients of various archival materials, the physical structure of documents, as well as the choice of signal parameters and terahertz imaging systems or configurations used to produce the terahertz image. This investigation was conducted systematically using historically informed models and historical documents, with different THz-TD set-ups and accessories, and complementary analytical and imaging tools. THz-TD imaging was found to be a useful non-invasive digitization technology for documents containing lamp black, carbon black or graphite but not for documents containing bistre, sepia, verdigris or Prussian blue. While deconvolution of the terahertz signal helps in distinguishing between layers in a complex document, it can also decrease the image contrast of inscriptions. The results further reveal the potential and limitations of the use of THz-TD spectroscopy for material identification in archival collections. Minium, vermilion and corrosive iron gall inks with excess iron(II) sulfate have a characteristic spectral signature below 3 THz, which can be extracted from the surface of an inked paper or parchment sheet. The project was developed in collaboration with TeraView Ltd, Cambridge, and Nationaal Archief (Netherlands).

Tiphaine completed an EngD degree at the UCL Institute for Sustainable Heritage in 2016, in association with the UCL EngD Centre in Virtual Environments, Imaging and Visualisation (VEIV). She completed the MRes Heritage Science at the Institute for Sustainable Heritage with Distinction in September 2012.

During her doctoral studies, Tiphaine was a post-graduate teaching assistant for the MRes Heritage Science at the UCL Institute for Sustainable Heritage and was awarded an international recognition as an Associate Fellow of the Higher Education Academy, UK. She was also a reviewer for the academic journal Studies in Conservation.

Tiphaine received an MSc in Physics and Nanoscience from the PHELMA, Grenoble-INP (France) Engineering School. She has always been interested in art and heritage, which is why she also attended the art school ESAD in Grenoble as a part-time student. Her research interests include heritage science, spectroscopic imaging and non-invasive techniques.

As part of a group project with other VEIV EngD students in 2011 - 2012, Tiphaine also participated in the design and installation of an audio micro-augmentation set-up in the Grant Museum of Zoology at UCL. Micro-augmentation is non-interactive and interpretation free, and supports implicit narration, causing emotional response to an unstructured museum experience. The set-up triggers directional sound signals related to a museum artefact when a visitor passes by, which are only distinctly heard by a visitor looking at directly the artefact. 

Publications in peer-reviewed journals

  • T. Bardon, R. K. May, P.F. Taday, and M. Strlic. Systematic study of terahertz time-domain spectra of historically informed black inks. Analyst, 138:4859–4869, 2013.
  • T. Bardon, R. K. May, P. Taday, and M. Strlic. Influence of particle size on optical constants from pellets measured with terahertz pulsed spectroscopy. IEEE Transactions on Terahertz Science and Technology, [Accepted] DOI: 10.1109/TTHZ.2016.2538641, 2016.
  • M. T. Ruggiero, T. Bardon, M. Strlic, P. F. Taday, and T. M. Korter. Assignment of the Terahertz Spectra of Crystalline Copper Sulfate and Its Hydrates via Solid-State Density Functional Theory. The journal of physical chemistry A, 118:10101 – 10108, 2014.
  • M. T. Ruggiero, T. Bardon, M. Strlic, P. F. Taday, and T. M. Korter. The role of terahertz polariton absorption in the characterization of crystalline iron sulfate. Physical chemistry chemical physics : PCCP, 17:9326–9334, 2015.

Oral and poster presentations at international conferences

  • T. Bardon, R. May, B. Jackson, P. F.  Taday, and M. Strlic. A systematic study of historic writing and drawing inks using THz-TD spectroscopy and imaging. In 'O3A: Optics for Arts, Architecture, and Archaeology', 2013 Optical Metrology Technical Summaries, Munich, Germany, May 2013. SPIE. [available online]
  • T. Bardon, R. K. May, P.F. Taday, and M. Strlic. Optical Properties of Archival Materials in the Range 0.15 3 THz. In 'THz-ARTE Workshop Program', ENEA-Frascati, Rome, Italy, December 2014. [available online]
  • T. Bardon, R. K. May, B. J. Jackson, G. Beentjes, G. de Bruin, P.F. Taday, and M. Strlic. Contrast and readability in terahertz time-domain images of ink inscriptions: A comparative study of model and historical documents. In 'Lasers in the Conservation of Artworks (LACONA) X, Conference Program', Sharjah, United Arab Emirates, June 2014. [available online]
  • T. Bardon, R. K. May, P.F. Taday, and M. Strlic. Undressed! Characterizing Documents And Revealing Their Hidden Texts With Terahertz. In 'Third International Congress on Chemistry for Cultural Heritage (CHEMCH 2014)', Book of abstracts, Vienna, Austria, July 2014. [available online]
  • T. Bardon, R. K. May, P. Taday, and M. Strlic. Material characterization of historical parchment using terahertz time-domain spectroscopy. In 'Proceedings of the 39th International Conference on Infrared, Millimeter, and Terahertz Waves', Tucson, AZ, USA, September 2014.  [available online]
  • T. Bardon, P. F. Taday, G. de Bruin, and M. Strlic. Interpreting terahertz images of ink inscriptions. In '1st International Conference Science and Engineering in Arts, Heritage and Archaeology', Book of Abstracts, London, UK, July 2015. SEAHA CDT.  [available online] 
  • T. Bardon, R. K. May, G. de Bruin, P.F. Taday, and M. Strlic. Characterization and Imaging of Archival Texts: Lets Have a Word with Terahertz! In '2015 Eastern Analytical Symposium and Exposition', Book of Abstract, Somerset, NJ, USA, November 2015.  [available online]