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MA-XRF and OCT techniques as tools for identification of past renovation attempts as well as aid in current restoration treatment of the painting ‘Christ before Caiaphas’

Anna Faron

Abstracts

The aim of this work is to present an integrated approach based on various types of analyses of an oil-on-canvas painting to investigate layers of overpaint and varnishes added throughout the centuries. The project focused on an extremely overpainted altar-painting ‘Christ before Caiaphas’. MA-XRF and OCT were employed as diagnostic techniques.

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Purpose

1The aim of this work is to present an integrated approach based on various types of analyses of an oil-on-canvas painting to investigate layers of overpaint and varnishes added throughout the centuries. Simultaneously to the non-destructive research methods, samples were taken and investigated micro-chemically.

The Painting

2This project was conducted as a part of conservation-restoration diploma project focusing on an extremely overpainted altar-painting ‘Christ before Caiaphas’, painted in oil on canvas (late 18th century, Calvary of Pakość, Poland, size 148 x 96 cm). Due to previous improper restoration treatments of the painting some examination methods, like the UV-excited fluorescence of the surface of the paint surface, were difficult to interpret.

Methods

3Macro X-Ray Fluorescence scanning (MA-XRF) is an imaging technique which enables extended surface scans over thousands of square centimetres during a single examination. For this study the M6 JetStream scanning system from Bruker Nano GmbH was employed. It permits large surface scans – up to 70 cm x 55 cm with lateral resolution up to 50 µm. It comprises an X-ray source working at 50 kV/600 µA conditions with Rh anode and polycapillary optics. An open-air system permits imaging elements of atomic numbers not lower than 16 (sulphur).

4Optical Coherence Tomography (OCT) (ill. 1) is an interferometric non-contact and non-invasive technique of depth-resolved imaging (to obtain cross-sectional images) within media that scatter and/or absorb near-infrared light moderately. For examination a high resolution (2 µm axial, 12 µm lateral) spectral domain OCT instrument was used. A beam of near-infrared (770-970 nm) radiation of 0.8 mW was directed towards the object’s surface.

Fig.1 OCT tomograms

Fig.1 OCT tomograms

OCT tomograms give information about the sequence, thickness and condition of semi-transparent sub-surface layers such as varnishes and some overpaints. Additionally, OCT was employed to control the process of removing the layers of overpaints as well as thinning/removal of the varnish. (a) Tomogram collected before cleaning and removal of overpaints and varnish; (b) the result of the cleaning treatment.

Credits: Anna Faron, Magdalena Iwanicka

Fig. 2 Results of MA-XRF analysis

Fig. 2 Results of MA-XRF analysis

Caption: Assembled scans show distribution of some chemical elements. The resulting maps contain three separate scans put together in a graphic software.

Credits: Anna Faron, Magdalena Iwanicka

Conclusions

5Data acquired with MA-XRF (Fig. 2) revealed the distribution of different elements and therefore enabled not only identification of pigments, but also differentiation between primary and secondary layers which was essential for planning the conservation-restoration project with the best possible knowledge.

6With the precision enabling separation of almost every brushstroke, the subsequent phases of overpainting could be differentiated. Moreover, the MA-XRF analysis enabled assessment of the condition as well as composition of the original layers even before removing of the overpaint layers. It also allowed dating of some of the interventions, deduced from the materials that were detected.

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Attachment

  • Faron (application/msword – 1.5M)
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List of illustrations

Title Fig.1 OCT tomograms
Caption OCT tomograms give information about the sequence, thickness and condition of semi-transparent sub-surface layers such as varnishes and some overpaints. Additionally, OCT was employed to control the process of removing the layers of overpaints as well as thinning/removal of the varnish. (a) Tomogram collected before cleaning and removal of overpaints and varnish; (b) the result of the cleaning treatment.
Credits Credits: Anna Faron, Magdalena Iwanicka
URL http://ceroart.revues.org/docannexe/image/5080/img-1.jpg
File image/jpeg, 524k
Title Fig. 2 Results of MA-XRF analysis
Caption Caption: Assembled scans show distribution of some chemical elements. The resulting maps contain three separate scans put together in a graphic software.
Credits Credits: Anna Faron, Magdalena Iwanicka
URL http://ceroart.revues.org/docannexe/image/5080/img-2.jpg
File image/jpeg, 995k
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References

Electronic reference

Anna Faron, « MA-XRF and OCT techniques as tools for identification of past renovation attempts as well as aid in current restoration treatment of the painting ‘Christ before Caiaphas’ », CeROArt [Online], HS | 2017, Online since 30 May 2017, connection on 21 September 2017. URL : http://ceroart.revues.org/5080

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About the author

Anna Faron

Master student, Institute for the Study, Restoration and Conservation of Cultural Heritage, Nicolaus Copernicus University, Toruń, Poland. Study supervised by Professor Bogumiła Rouba, Assistant Professor Elżbieta Szmit-Naud, Magdalena Iwanicka PhD. faron.ania@gmail.com.

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Copyright

Licence Creative Commons
CeROArt – Conservation, exposition, restauration d'objets d'arts est mis à disposition selon les termes de la licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International.

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