sito infn ISTITUTO NAZIONALE DI FISICA NUCLEARE
Sezione di Genova
DIPARTIMENTO DI FISICA
Università di Genova



Cultural Heritage



IBA techniques in Archeometry

Any human artefact bears the history of its making, use, and conservation. Fossils as well bear the history of their birth, of their life, of the aggression of nature after their death. Reading this history is the ultimate goal of all the scholars and sciences that operate in the broad environment of the cultural heritage. Part of the history is visible. The expert eyes of an art historian, trained by thousands of examinations and supported by a sound knowledge of an historic period, can detect in the form of bodies, in the shades of colours, in the length and thickness of brush-strokes, the unmistakable signature of a master. A large part of the history is however hidden, lying below the surface, trapped in the texture of the object or deeper in the constituent atoms and molecules. The preparatory drawing of a painting, the artist’s second thoughts and remakes, the technology of preparing a colour, of firing pottery, of soldering metals, the signs of climate in a fossil, all require instruments to be read. These are the foundations of archaeometry. In this context, IBA analytic techniques have shown in the past to be able to play an important and fundamental rule. The number of museum objects a priori interesting to be analyzed is really huge, but their value, as well as the need of their safeguard and preservation and their complexity, often dissuade from applying analytic chemical techniques even on micro-samples extracted from art works. On the contrary IBA techniques, mainly PIXE, RBS, PIGE respect important operative criteria:

The employ of these techniques must take into account that every document or art work represents a single case, having unique problems and requiring specific analysis procedures which are settled by art historians and analysts together. The main techniques are:

Our Laboratory traditionally uses PIXE technique, by which can be analyzed all inorganic materials, even if mixed in the same object to organic materials. We can for example analywe a gem, such as a ruby, a metallic ink on an organic paper base, an inorganic pigment suh as cinnabar, mixed with an organic "glue" as linseed oil is. In some cases PIXE becomes a really unique ideal technique, for exaple in the analysis of drawings made by dry tip (silver or lead) on parchment, where the particle beam spot is comparable with the size of the drawn and PIXE sensitivity for metals is excellent, being instead insensitive to the organic substrate. There are also cases where PIXE suffers instead some limitations. PIXE analysis of a metal alloy (an ancient coin, for example) is limited in depth to thickness of a few microns, and the analyzed material is mainly made by the oxides and carbonates surface patina than by the object itself.


SOME EXAMPLES


Glazed Sculpture of della Robbia

Some of the most representative productions of the Italian Renaissance, are certainly the sculptures made by glazed ceramics (figure 1) related to Luca Della Robbia (figure 2) and his family. For more than one century the "robbian" production had a remarkable artistic value and a sizeable commercial success, so that it was widely imitated by coeval sculptors such as Benedetto e Santi Buglioni. The presence of many of such art works in today's artistic patrimony attests the wideness of that production and reminds the opportunity to setup a data base of analytical informations, complementary to historical and stylistic considerations, to be used in the restoration activity, in the attribution of the works, in the understanding of the manufacturing used techniques.




Fig 1. cross-section of a Renaissance glaze seen by an electronic scanning microscope. Gas bubbles (B), quartz chrystals (Q), opalescent tin bioxide chrystals (C), and the clay-glaze inerface (I) are visible.




Fig 2. young boy portrait by Luca Della Robbia during PIXE analysis at the KN 3000 accelerator. By gentle permission of Museo Civico Gaetano Filangieri in Naples.


Starting from 1998 a wide international collaboration including, besides our laboratory, INFN Laboratory in Florence, Louvre Museum, and Opificio delle pietre dure in Florence, dealt with the analysis of the coloured glazes of "robbian" production (figure 1) on different samples (whole art works, fragments, SEM sections) and a sizeable number of art works.


Fig 3 Progression of the number of analysis on "robbian" art works and reference standards since september 1998 to december 2001.

Due to the large number of analyzed samples, it was possible to find out important correlations among the elements composing robbian glazes, Fe, Co, Ni and As shown in figure 4



More recently the collaboration has beeen extended to INFN Laboratory in Catania and to Museo del Bargello for the "in situ" analysis of twelve robbian art works.




Figura 5Madonna del Roseto by Luca della Robbia during "in situ" analysis performed with portable instruments a-PIXE (L.N.S.). By gentle permission of Museo Nazionale del Bargello



Pigments od early Middle Ages from Palazzo dei Provveditori di Cividale

National archeological museum of Cividale del Friuli includes an important collection of decorative and structural architectonic elements typical of Venetian-Byzantine style. Among the decorative elements, twelve paterae and three panels supported with a centre in relief. Among the structural elements, five pillars, five shelfs and several fragments (figure 6). All these objects show phytomorphe decorations and fights among animals, and are functionally and dimensionally correlated. Dating, on stylistic base, places them at the second half of 12th century, when Cividale was the residence of Aquileia Patriarch, the second authority of the churche after the Pope. Instrumental analysis of the remaining pygments has been carred on with different techniques (PIXE, SEM-EDS, Raman) in order to verify the common origin of the pieces, both for the production shop, and the hosting building. The typology of pygments and use of precious materials support the hypothesis that these pieces would come from the patriarchal palace before the reconstruction following the ruinous fire in 1186.


Fig 6. Middle Ages architectonic elements from Palazzo del Patriarca in Aquileia under PIXE, SEM and RAMAN analysis. By gentle permission of Museo Archeologico in Cividale.



Fig 7 PIXE spectra of blue samples from National Archeological Museum in Cividale lead to the identification of lapis-lazzuli, of certain Middle Ages origin, and of a modern pygment, probably used for a partial restoration (of which today no traces remain) at the early 800.


For a further deepening about PIXE technique applied to the Archeometry we refer to:
" Ion beam study of art and archaeological objects " di G. Demortier


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