Raman study of a work of art fragment

📝 Abstract

The purpose of the present report was the study and identification of an unspecified sample on a work of art by means only of a microscope coupled to a Raman spectrometer. The origin of the fragment was unknown. The Raman spectra on the virgin sample were giving no results because of a deteriorated surface treatment, in spite of the evident blue color identified by microscopic visual inspection. The sample fragmentation and the preparation of a KBr pellet allowed the distribution of the painting layers of the different components on a flat substrate reducing surface effects. Selecting the areas of different color and focusing there it was possible to identify the pigments from their Raman spectra locally acquired by selective excitation. Raman spectra were assigned by comparison with published databases. It was possible to connect Carbon Black and Orange iron oxide, as documented historically, as constituents of Azurite preparatory layer Morellone, according to a technique generally employed to allow the use of Azurite blue pigment on frescos, consequently the identification of typology of work of art was deducted and attributed to a fresco.

💡 Analysis

The purpose of the present report was the study and identification of an unspecified sample on a work of art by means only of a microscope coupled to a Raman spectrometer. The origin of the fragment was unknown. The Raman spectra on the virgin sample were giving no results because of a deteriorated surface treatment, in spite of the evident blue color identified by microscopic visual inspection. The sample fragmentation and the preparation of a KBr pellet allowed the distribution of the painting layers of the different components on a flat substrate reducing surface effects. Selecting the areas of different color and focusing there it was possible to identify the pigments from their Raman spectra locally acquired by selective excitation. Raman spectra were assigned by comparison with published databases. It was possible to connect Carbon Black and Orange iron oxide, as documented historically, as constituents of Azurite preparatory layer Morellone, according to a technique generally employed to allow the use of Azurite blue pigment on frescos, consequently the identification of typology of work of art was deducted and attributed to a fresco.

📄 Content

Article Raman study of a work of art fragment
Barbara Federica Scremin 1,* 1 National Nanotechnology Laboratory (NNL) - CNR Nanotech Institute, via per Arnesano km 5, I- 73100 Lecce, Italy; E-Mail: barbara.scremin@unisalento.it, barbara.scremin@cnr.it

• Author to whom correspondence should be addressed; E-Mail: barbara.scremin@cnr.it;

Premise: The present work was not published on scientific journals because presently it is required to have informations about the whole work of art as provenience in location and about sampling. Such data were not available to the author. Therefore the author considers of importance the divulgation of the present study for the method that makes clear how is possible to carry on a Raman analysis and to extract the maximum of informations from few beginning data, which is doubtless fascinating. Procedures were examined step by step and can be easily followed thanks to the accompanying pictures. The only instrument used was a Raman microscope. It can be useful especially to students that just faced the subject of work of art investigation with Raman spectroscopy.

Abstract: The purpose of the present report was the study and identification of an unspecified sample on a work of art by means only of a microscope coupled to a Raman spectrometer. The origin of the fragment was unknown. The Raman spectra on the virgin sample were giving no results because of a deteriorated surface treatment, in spite of the evident blue color identified by microscopic visual inspection. The sample fragmentation and the preparation of a KBr pellet allowed the distribution of the painting layers of the different components on a flat substrate reducing surface effects. Selecting the areas of different color and focusing there it was possible to identify the pigments from their Raman spectra locally acquired by selective excitation. Raman spectra were assigned by comparison with published databases. It was possible to connect Carbon Black and Orange iron oxide, as documented historically, as constituents of Azurite preparatory layer - “Morellone”, according to a technique generally employed to allow the use of Azurite blue pigment on frescos, consequently the identification of typology of work of art was deducted and attributed to a fresco.
Keywords: Azurite; iron oxide, carbon black, pigments identification; fresco; Raman microscopy, restoration; conservation

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1. Introduction The context of this work is the field of composition identification on a work of art that should be performed before a restoration and conservation intervention. Research Institutions, Universities, museums Research Sections are interested in the scientific study of work of arts. In Italy they may perform independent work or collaborate with peripheral Organs (“Soprintendenza ai Beni Culturali”), with a regional character, of the Ministry of Cultural Heritage and Activities (the Culture Ministry of Italian Republic). Among the activities of “Soprintendenze ai beni Culturali” are the identification of work of arts, their finding investigation and successive binding command for their protection and control by means of specific permits on works of restoration. Moreover “Soprintendenze” make rules on work of arts transfers, exports and on projects of landscape interest. Therefore each conservation intervention, particularly on “bonded” historical artifacts including buildings, must respect specific rules established by “Soprintendenze” and the specific protocol applied in the intervention need their approval. The work of restoration must respect rules, according to the best scientific acquired knowledge and technological progresses. Works of arts periodically need conservation and restoration intervention especially if they are exposed in the natural environment and are not in a museum under strictly controlled climatic and illumination condition: materials degrade over time, and once identified, over their characteristic time. Each intervention should be reversible as a criterion, and documented. A conservation and restoration intervention first of all requires a scientific identification of materials and their assembling methods, because the respect of the original formulation and of its expressive value must be preserved as a cultural value. The new materials should match at the best the original ones chosen by the artist since they are part of the historical value of an artifact: they can tell us about the socio-economic context, the technical and philosophic evolution of an artist or of an era.

Scientific studies on work of arts are necessary preliminary steps of any action of restoration aiming at the reestablishment of the original status of the elements constituting the artwork. Now days it is praxis to document the steps of any restoration intervention aiming at the conservation and repair of cultural heritage items. Conservation actions are known

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