Spectroscopic Imaging in Art Conservation

Analysis of materials of cultural heritage collections has a vital role in a responsible modern approach to conservation.  We apply ATR-FTIR spectroscopic imaging to cross-sections from cultural heritage paintings and objects to reveal the chemical composition and to understand the degradation processes in paintings from the National Gallery and other museums.  This information is crucial for conservation practices and our ability to preserve our national collections for future generations.

In addition to the specific findings for each painting, there are a number of general conclusions which can be drawn from this work. Most importantly it has been shown that micro ATR-FTIR imaging can achieve a high spatial resolution (ca. 3 - 4 μm) on paint cross sections; enabling paint layers and even individual particles to be identified, which is not yet possible using other techniques.

The samples chosen were those which had been particularly difficult to characterise using the traditional techniques and where the degradation seen is typical of many similar paintings. Characteristic absorption bands were identified for many of the components present in these complex samples. This methodology is also able to provide a fast qualitative approach for analysis of both organic and inorganic components in a way that is noninvasive for the sample so that it can be examined using multiple analytical techniques. In addition, combining spectroscopic imaging with chemometric analysis allows the wealth of information contained in any one infrared image to be extracted efficiently. Using chemometrics, various multivariate approaches can be conveniently adapted to focus on specific problems left unsolved by univariate analysis. It was demonstrated that ATR-FTIR imaging allows a better understanding of the spatial distribution of components within the samples, from which valuable information about the behaviour of materials within the paintings can be deduced. 

The application of macro ATR-FTIR imaging using a diamond accessory, provides a greater field of view (ca. 1 mm²) but a lower spatial resolution (ca. 15 μm), to both cross-sections and surface samples of wall paintings has also been shown to be feasible.

In collaboration with the Royal College of Art and the National Archives, we have also applied ATR-FTIR spectroscopic imaging to cross-section samples of albumen photographs. The preservation of early 20th century, late 19^th century albumen prints is of great concern to collection managers and conservators of photographic materials. The results of ATR-FTIR imaging provided important information about the chemical composition of these samples.

Our group has developed active collaboration in this area with the National Gallery, the British Museum, the Victoria and Albert Museum and other London museums with a successful recent grant from the AHRC. Our contribution in examining objects of cultural heritage is valuable for preservation of important artworks. Following successful collaboration with our group (see image below), the National Gallery has now adopted micro ATR imaging for their conservation practices with the aim to understand the degradation processes in paintings for their conservation practices.  We are developing collaboration with the British Library and Matenadaran (Armenia) on studies of degradation of historic leather and parchment with FTIR spectroscopic imaging. 

Our most recent papers in this area are Possenti E. et al "Time resolved ATR-FTIR spectroscopy and macro ATR-FTIR spectroscopic imaging of inorganic treatments for stone conservation" Analytical Chemistry  (2021) 93 (44), 14635-14642 (doi) and an invited review article  by Liu G. L. and Kazarian S. G. "Recent advances in studies of cultural heritage using ATR-FTIR spectroscopy and ATR-FTIR spectroscopic imaging"   Analyst, (2022) 147  https://doi.org/10.1039/D2AN00005A   Open Access

Key References

• Ricci C., Bloxham S., Kazarian S. G., ATR-FTIR imaging of albumen photographic prints, J. Cultural Heritage 8 (2007) 387-395
• Spring M., Ricci C., Peggie D., Kazarian S. G., FTIR imaging for the analysis of organic materials in paint cross sections: case studies on samples from paintings in the National Gallery, London, Anal. Bioanal. Chem. 392, 37-45 (2008). (doi)
• Joseph, E., Ricci, C., Kazarian, S.G., Mazzeo, R., Prati, S., Ioele, M. Macro-ATR-FT-IR spectroscopic imaging analysis of paint cross-sections Vibrational Spectroscopy (2010) 274-278. 
• Kazarian S. G. Recent Advances in FTIR Imaging International Workshop on Characterisation of Organic Materials in Paint Cross Sections. Bologna, Italy, 2007.
• Kazarian S. G. Enhancing studies of objects of cultural heritage with FTIR spectroscopic imaging Technart- 2013: Analytical Spectroscopy in Art and Archaeology, Amsterdam, Netherlands, September 2013
• Kazarian S. G. Enhancing Studies of Objects of Cultural Heritage with Spectroscopic Imaging Gordon Research Conference on Scientific Methods in Cultural Heritage Research,  USA, August 2014.
• Kazarian S. G.,  invited plenary lecture  Spectroscopic imaging: new trends and emerging applications to the objects of cultural heritage at the the 12^th Infrared and Raman Users Group (IRUG biennial Conference) Greece, May 2016.
• Kazarian S. G., invited lecture at the international conference on “Novel technologies for conservation and restoration of ancient manuscripts” in Yerevan, Armenia at Matenadaran (research institute and museum, as well as one of the largest repository of ancient manuscripts in the world),  September 2017.
• Gabrieli F., Rosi F., Vichi A; Cartechini L, Buemi L. P., Kazarian S. G., Miliani C.  Revealing the nature and distribution of metal carboxylates in Jackson Pollock’s Alchemy (1947) by micro attenuated total reflection FTIR spectroscopic imaging  Analytical Chemistry (2017) 89, 1283-1289.  (doi).
• Vichi A., Eliazyan G.,  Kazarian S. G. Study of the degradation and conservation of historical leather book covers with macro ATR-FTIR spectroscopic imaging   ACS Omega (2018) 3(7), 7150-7157 (doi).  Open Access article and EDITOR's CHOICE.