Raman microscopy in archaeological science

Raman spectroscopic analysis of the Maya wall paintings in Ek’Balam, Mexico

The identification of copper oxalates in a 16th century Cypriot exterior wall painting using micro FTIR, micro Raman spectroscopy and Gas Chromatography-Mass Spectrometry

The reproduction of an old recipe to obtain the pigment known as verdigris leads to a complex mixture of hydrated copper(II) acetates containing neutral verdigris and two varieties of basic verdigris. Since the characterization of such mixture is complicated by the lack of reference standards, we complemented our Raman measurements with Fourier transform infrared (FTIR) and X-ray diffraction (XRD) experiments to perform our analysis, which has been compared with available studies. The spectral analysis allowed us to distinguish the different verdigris varieties, with stretching and bending wavenumbers assigned to the following chemical groups: OH groups (OHhydroxy and OHH2O) (3600–3050 cm−1), CuO bonds (CuO and CuOH) (1000–450 cm−1) and those corresponding to the acetate group (CH3COO−), i.e. (CH3: 3000–2850 cm−1) and (COO−: 1600–1400 cm−1 and 700–600 cm−1). Both wavenumbers and Raman intensities were used to quantify the relative compositions of the mixture components. Copyright © 2010 John Wiley & Sons, Ltd.

Verdigris pigment: a mixture of compounds. Input from Raman spectroscopy

This paper presents the results of scientific examinations carried out on an Egyptian bronze statue discovered buried in Sais. Optical Microscopy (OM), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) were used to understand the corrosive morphological characteristics of the patina, to investigate the corrosion products, analyze the elementary composition of the statue and to identify the corrosive factors with effects on the alteration processes. The results indicated that the statue was made of bronze alloy, with copper as the main element, besides lead and tin. Three layers of alteration products with various composition and morphology covered the substrate of the bronze alloy. XRD results indicated that the statue was subjected to many corrosive ions such as sulfur and chloride, and buried in wet soil, rich in oxygen and carbon. This study provides useful information for the restoration and protection of the statue.

The characterization of a corroded egyptian bronze statue and a study of the degradation phenomena

A new pale blue corrosion product has been found on copper alloy artifacts in the collections of a number of institutions. The corrosion product has been characterized using X-ray powder diffraction, X-ray photoelectron spectroscopy, wavelength X-ray dispersive spectroscopy and Raman microspectroscopy. The corrosion product is a copper(II) compound, containing copper and sodium in a ratio of approximately 1:1 along with formate and acetate groups. It is speculated that formic (methanoic) and acetic (ethanoic) acid vapors arising from materials used to house the objects contribute to the formation of this compound.

D. Scott

Papers

The characterization of a new pale blue corrosion product found on copper alloy artifacts