The composition of an alloy and the nature and degree of its corrosion are studied to establish a body of evidence that indicates the chronological compatibility of the object with the presumed period of manufacture.
Studies are carried out to characterise the components of the alloy, its corrosion features and the composition of different deposits. In some cases, the surface state of the incised decoration is also studied.
With an extensive background in archaeomaterial physics and chemistry, Dr. Olivier Bobin, the scientific manager at Ciram Laboratory based in France performs the metallurgy analysis. Since 2000, the focus of his work has been in investigating and analyzing works of art and objects of significant cultural heritage using coupled methodologies. His research continues to be in the use of new analytical methods for the study of ancient materials focusing on dating methods and characterization of corrosion processes.
In Asia, Antique Authentication is the sole agent for Ciram.
Bronze, brass, iron, silver and gold objects that are at least 300 years old can be considered for analysis.
Metallurgical studies for bronze, brass, iron and silver are carried out using a stereomicroscope, a metallographic microscope and a Scanning Electron Microscope (SEM) with back-scattered electron imaging (BSE) and pseudotopography imaging (TOP) coupled with an energy dispersive and X-ray spectrometer (EDS), which performs X-Ray fluorescence spectra.
The first step of the analysis is to define the composition of the alloy and the nature of the embedded inclusions. Elements of modernity, such as aluminum or phosphorous, can be detected at this point and/or the incompatibility of the composition of the alloy with the presumed date of the object.
The composition’s compatibility with the presumed period of the object cannot be considered as fundamental proof of authenticity. Further observations of corrosion expansion inside the alloy should also be evident. The physic-chemical features need to also be defined, such as inter-granular and trans-granular corrosion, the weathering of lead globules and their shift to the surface, the superficial increase of tin associated with the corrosion of the copper rich phase, dezincification in the case of brass objects, the composition of corrosion products and any evidence of chemical treatments.
Due to the lack of corrosion, gold objects are more difficult to analyse, and SEM is coupled with PIXE, or ICP/MS.
Within four to five weeks, a comprehensive report is provided explaining the experimental methods, analysis of the metal’s composition with EDS spectra, analysis of the degree of corrosion with SEM micrographs, analysis of the corrosion products with EDS spectra, a discussion of the findings and conclusions which are given as consistent or inconsistent with the presumed period.
Should the findings indicate the object has been subjected to modern chemical treatment, this will also be stated.
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