μ-Raman Spectroscopy Analysis of Ancient Ceramics

Because of its nondestructive nature, μ-Raman spectroscopy is used in various industries, including food and beverage analysis, pharmaceuticals, and even art analysis. Recently, a research team from the Center for Research on Archaeometry and Conservation Science in Naples, Italy, highlighted the utility of μ-Raman spectroscopy in analyzing ancient ceramics. The findings of this study were published in the journal Applied Clay Science (1).

Clay minerals are resources often used in ceramics. Clay raw materials, over the course of human history, have demonstrated value in various aspects of socio-cultural life. For example, clay materials have been used in agriculture, civil engineering projects, and even contributed to the stimulating of civilization economies (2). Because of this, studying ceramics also helps archaeologists establish a historical record (3).

Intact pottery jars labeled in a forgotten script. Generated with AI. | Image Credit: © Natalia - stock.adobe.com

In recent decades, μ-Raman spectroscopy has emerged as a powerful tool for studying ceramics because of its ability to perform fast, reproducible, and reliable analyses (1). This study underscores the capability of μ-Raman spectroscopy to offer comprehensive data that surpass traditional methods.

μ-Raman spectroscopy can be used to discover new information about ancient ceramic production techniques, as well as firing conditions. For their study, the research team selected pottery fragments characterized by a variegated color zonation, which is indicative of uncontrolled firing conditions (1). These fragments were subjected to a series of in-depth analytical techniques, both conventional and innovative, to evaluate the reliability and effectiveness of μ-Raman spectroscopy.

Several analytical methods were used in this study. These techniques include hydric tests, mercury intrusion porosimetry, X-ray diffraction, X-ray fluorescence, Mössbauer spectroscopy, fiber optical reflectance spectroscopy, and optical and scanning electron microscopies. These methods provided a broad spectrum of compositional and mineralogical data (1). However, when compared to the results obtained from μ-Raman spectroscopy, the team found that the latter offered more detailed and accurate insights into the firing temperatures, oxidative steps, and provenance of the raw materials used (1).

The researchers discovered in the study that μ-Raman spectroscopy can constrain the firing temperatures. The data indicated that the ceramics were fired at temperatures between 900 and 950 °C (1). This was corroborated by the mineralogical and spectroscopic evidence of the prograde 10 Å dehydroxylated phyllosilicates, a significant marker in the analysis of firing conditions (1). Additionally, the study revealed the development of Fe(III) oxides at the rims of the sherds and Fe(II)-bearing phases at their cores, further illuminating the effects of the not well-controlled firing atmosphere (1).

By using μ-Raman spectroscopy, the research team also learned more about the materials used in pottery and ceramics. For example, the analysis suggested that the ceramics studied were composed of a low-CaO base clay mixed with volcanic temper from the environs of Mount Vesuvius, which was an active volcano during ancient Rome (1).

This study highlights the potential of μ-Raman spectroscopy in archaeological research, particularly in analyzing non-homogeneous samples. μ-Raman spectroscopy improves on traditional methods because it allows for rapid analysis without compromising the integrity of the samples (1). Because archaeology relies on the study of artifacts, it is integral that samples remain intact throughout the analysis and preservation processes.

The ability to perform precise, non-destructive analyses on ceramics can revolutionize conservation science, providing new methods for preserving and understanding cultural heritage (1). Furthermore, the successful application of μ-Raman spectroscopy in this study sets a precedent for its use in other fields, such as materials science and geology, where detailed compositional analysis is essential.

References

(1) Germinario, C.; Cultrone, G.; De Bonis, A.; et al. μ-Raman Spectroscopy as a Useful Tool for Improving Knowledge of Ancient Ceramic Manufacturing Technologies. Appl. Clay Sci. 2024, 253, 107347. DOI: 10.1016/j.clay.2024.107347

(2) Konta, J. Clay and Man: Clay Raw Materials in the Service of Man. Appl. Clay Sci. 1995, 10 (4), 275–335. DOI: 10.1016/0169-1317(95)00029-4

(3) Tite, M. S. Ceramic Production, Provenance and Use–A Review. Archaeometry 2008, 50 (2), 216–231. DOI: 10.111/j.1475-4754.2008.00391.x