The surface degradation of Baltic amber: The depth‐profiling analysis and its application to historical object

Abstract

A depth profile‐scanning study of an 18th‐century gun‐powder horn as well as reference Baltic amber samples was performed using a Raman confocal microscope equipped with a 785‐nm laser. It was found that spectra collected from the surface are different than those from the bulk. The main changes are observed in the 1,700–1,400 cm−1 range and are caused by degradation of the amber. The degraded layer was characterized mainly by an increase of the 1,615 cm−1 band ascribed to the ν(CC) characteristic of aromatic rings and a decrease of the 1,645 cm−1 band ascribed to the ν(CC) of nonconjugated structures. The degraded layer is estimated at 100–150 μm, where the spectra gradually resembled the spectrum of nondegraded amber. Analogous changes were observed both for the reference samples and for the abovementioned historical object. The observed spectral changes suggest that this technique could be utilized for studying the degradation of amber artifacts in museum collections.

Applications of Raman spectroscopy in art and archaeology

“…Confocal μ‐Raman spectroscopy, equipped with an excitation laser at 785 nm, was used by Rigula et al [ 20 ] to perform a depth‐profiling study of an 18th century gun‐powder horn. Also, the Raman characterization of different reference Baltic amber samples was performed to have an adequate database for comparison purposes.…”

Determination of Anthracene Derivatives in Baltic Amber Using SERS

“…The Raman spectroscopy technique is effective for the analysis of natural resins, allowing the accurate identification of their chemical structures and their changes [ 28 , 29 , 30 ]. Some of the latest papers are aimed at modeling the spectral components of amber [ 31 ], the study of the chemical composition of amber of various geographical origins [ 32 ], the study of the problems of amber oxidation [ 33 ], and changes in the structure of amber during thermal action applications [ 34 ]. However, this type of spectroscopy in the study of amber is less common in contrast to IR spectroscopy.…”