The scientific contribution in support of cultural heritage preservation is vast and complex, often relying on multidisciplinary approaches. Together with other fields, such as engineering and material science, over the years, analytical chemistry has played a significant role in analyzing and preserving artifacts.
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Analytical chemistry is at the heart of preservation science. Physical artifacts are organic-inorganic systems and need comprehensive techniques that investigate different materials with high resolution and accuracy. Their analysis and characterization are the basis for developing the right preservation and intervention strategies.
With a great number of methodologies and tools available (i.e., molecular and elemental spectroscopic analysis, chemometrics, etc.), it is now possible to define the impacts of environmental stressors (both natural and anthropogenic), identify the decaying pathways of materials due to the surrounding environment, and inform the development of new remediation methods.
The Marvels of Cultural Heritage
As defined by the UNESCO Institute for Statistics, Cultural heritage is "the legacy of physical artifacts and intangible attributes of society inherited from past generations." Physical artifacts include archaeological and historical artifacts, works of art, literature, music, buildings, monuments, and historic places.
Whether referring to paintings from the Renaissance, coins from the Roman Empire, castles, palaces, or remnants of ancient civilizations, cultural heritage artifacts are unique and irreplaceable and must be preserved for future generations.
The Challenge of Preservation
Exposure to different environmental factors, such as light, temperature, and humidity, can cause the degradation of physical artifacts. For instance, air pollution, climatic conditions, and biological contamination can affect the preservation of particularly fragile artworks such as prehistoric paintings and engravings.
In addition, further threats arise from natural or anthropogenic disasters and wrong restoration interventions, posing serious challenges to cultural heritage preservation.
There are many ways analytical chemistry can contribute to solving some of these challenges, ranging from the analysis of the composition and structure of cultural heritage materials (including information on provenance and manufacturing technology) to preserving, protecting, and securing artifacts against aging and degradation.
The Analytical Chemistry Revolution
Over twenty years ago, the UNESCO-ICOMOS (International Council of Monuments and Sites) provided guidelines about the investigation protocols for cultural heritage artworks and constructions, recommending non-destructive techniques as far as possible.
In the last decades, new analytical techniques applied to cultural heritage preservation have focused on non-invasive or non-destructive procedures. Moreover, the advent of portable instruments has boosted the development of methods for real-time analysis in the field (e.g., in museums).
With great advances in the capabilities of spectroscopic and chromatographic methods, significant developments in chemical imaging, and the potential of nanotechnologies and nanomaterials, many techniques are available that provide new solutions and perspectives in the preservation and restoration methods of artifacts.
Analytical Tools in Action
One of the first techniques to become widely applied in the preservation of cultural heritage is gas chromatography-mass spectrometry (GC-MS), often used in analyzing works of art, especially concerning both natural and synthetic binders. Similarly, different analytical strategies allow the characterization of drying oils, waxes, and terpenic resins used in paintings.
High-performance liquid chromatography (HPLC) is also a main analytical technique used to analyze and preserve paintings, drawings, sculptures, and textiles, whilst laser ablation-mass spectrometry equipped with an inductively coupled plasma source can be used to detect forgeries.
Much attention has been dedicated to Raman spectroscopy thanks to its ability to characterize organic and inorganic compounds. Other spectroscopic techniques that are mainly used for the elemental analysis of cultural heritage materials are energy dispersive X-ray fluorescence (EDXRF) and laser-induced breakdown spectroscopy (LIBS).
Very recently, the analysis of samples from the Mona Lisa by X-ray diffraction and infrared spectroscopy techniques revealed the presence on the ground layer of oil and lead white, together with plumbonacrite. The occurrence of these compounds (that confer specific drying properties to the paint) suggests that while other artists of the time used gesso, Leonardo Da Vinci experimented new techniques using led oxide.
Case Studies
The causes of the chemical degradation of a Roman mosaic at Palazzo Valentini (Rome, Italy) were assessed through a multi-analytical approach using a series of techniques, including GC-MS, infrared spectroscopy, nuclear magnetic resonance, and X-ray fluorescence.
The analysis revealed the presence of aliphatic hydrocarbons (octadecane and hexadecane), molecules containing N-H bonds (1-methylheptylamine and decylamine), and identified other complex compounds. Although this is still a preliminary investigation, the study may improve the knowledge of the Roman mosaic, enabling the identification of the most appropriate preservation strategy.
Another study investigated the mechanisms of rust formation and diffusion in stained marbles and carbonate stones using various analytical techniques, such as optical and scanning electron microscopy and Mössbauer and XPS spectroscopy.
The study aimed to determine the different oxidation states of iron and better understand the composition and evolution of iron-based rust stains. This may provide insights into the corresponding corrosion products and their evolution over time and inform the development of specific treatments for more effective and safe rust removal.
Conclusion
Hundreds of other examples highlight analytical chemistry's crucial role in safeguarding cultural heritage for future generations.
Particularly through non-destructive and non-invasive elemental or molecular techniques, analytical chemistry can allow a thorough understanding of cultural heritage materials and their degradation processes, helping to tackle current challenges and determine strategies for their restoration and preservation.
Sources
- Badea, E. (2019). Chemistry for cultural heritage: connecting past and future. Heritage Science, 7, 99.10.1186/s40494-019-0342-2. Available: https://doi.org/10.1186/s40494-019-0342-2
- Gonzalez, V., Wallez, G., Ravaud, E., Eveno, M., Fazlic, I., Fabris, T., Nevin, A., Calligaro, T., Menu, M., Delieuvin, V. & Cotte, M. (2023). X-ray and Infrared Microanalyses of Mona Lisa's Ground Layer and Significance Regarding Leonardo da Vinci's Palette. Journal of the American Chemical Society, 145, 23205-23213.10.1021/jacs.3c07000. Available: https://doi.org/10.1021/jacs.3c07000
- Colantonio, C., Baldassarri, P., Avino, P., Astolfi, M. L. & Visco, G. (2022). Visual and Physical Degradation of the Black and White Mosaic of a Roman Domus under Palazzo Valentini in Rome: A Preliminary Study. Molecules (Basel, Switzerland), 27, 7765.10.3390/molecules27227765. Available: https://pubmed.ncbi.nlm.nih.gov/36431866
- Reale, R., Andreozzi, G. B., Sammartino, M. P. & Salvi, A. M. (2023). Analytical Investigation of Iron-Based Stains on Carbonate Stones: Rust Formation, Diffusion Mechanisms, and Speciation. Molecules, 28, 1582. Available: https://www.mdpi.com/1420-3049/28/4/1582
Further Reading