Painting Cross-Section

‘Ideal’ Versus ‘Possible’ in Field of Scientific Investigation Nowadays

Marcia Rizzo, Professor of Superior Conservation Course / conservator,
PUC- SP Pontifical Catholic University of São Paulo, Brazil

The aim of this paper is to discuss the relationship between the
“ideal” and the “possible” in the field of scientific research applied
to conservation of cultural heritage. The scientific research on
works of art must be done very carefully. The non-destructive
analysis methods are preferred to the destructive. First of all the
question and the reason of this question must be clear. Then it’s
necessary to know that methods of analysis can give the expected
response, which of these methods are available and which are
possible to be applied to works of art. It’s necessary to think also
about whether the analysis will be done in situ or if the work
must be carried. If with withdrawal of samples or not. In other
words it is necessary to create a strategy and approach procedure.
However, as is known, it’s not always possible to use the ideal
procedure with all equipment and analysis desired. Sometimes the
restriction is imposed by the artwork itself, because of the size,
location, condition, etc.; other, by the project, deadlines, budgets,
resources, availability of equipment, materials, etc. It takes a very
broad knowledge in the scientific area to make the most appropriate
decisions.
To illustrate this, two examples will be discussed here: the
research done in the paintings on the ceiling of the Carmelite
church in SP, which used destructive methods, and the research
done in the oil painting Annunciation, which used non-destructive
methods. The paintings of Carmo Church in Sao Paulo, carried in
the eighteenth century and attributed to the great Baroque artist
Frei Jesuíno of Mount Carmel, had refinish on funds and central
figures. Original paints, as well as the subsequent interventions
were investigated scientifically through diverse methods based on
the use of complementary techniques and cross link of results, for
the purpose of timing layers and propose treatment of restoration.
The original materials and those added later were physicochemical
and analytically characterized. For this purpose samples
of repainting and micro-samples from the original painting were
taken. The following techniques were employed: cross-section of
the pictorial layer; microscopic observation by binocular microscope
and scanning electron microscopy with energy dispersive
analyzer of X-ray the Annunciation painting made by Swedish artist Fredrik Westin (1782-1862), presented refinishing in several
areas. It was possible to identify these areas through observation
with UV radiation. The original pigments and the paints added
later were characterized with a portable fluorescence X-rays Tracer
III-SD da Bruker. In this case it was not necessary to remove
samples. Whenever possible, the ideal is to make the scientific
investigation of works of art with non-destructive methods in situ
analysis, analyzing the front of pictorial layer; however sometimes
it is necessary to observe directly the overlapping strata. And in
these cases the withdrawal of samples could be required. It is
important to assess whether the response I intend to get justified
the use of a destructive method of analysis. The investigation
made at Carmo’s Church contributed to reveal a very important
painting and also part of Brazilian history.

The exhaustive technical analysis of a major Mexican enconchado
depicting the Adoración de los Magos, a painting by Juan
González de Villaverde (active between 1689 and 1698), uncovered
an extraordinarily complex and sophisticated technique: it
revealed combinations of different binding agents, as well as the
widespread use of organic colorants, gold and silver. The interpretation
of the cross-section successions was also especially
revealing, as it provided a completely new perspective on works
of this nature, as opposed to the vague, incomplete technical references
hitherto to be found in the literature.
All the data we have collected and the conclusions we have
reached are of considerable help when addressing possible conservation
and restoration procedures, as they minimise the obvious
risk that is always involved due to the lack of knowledge
regarding the painting techniques involved.

Identification of the painting technique adopted by an artist is often debated in studies on the characterization, restoration and conservation of mural paintings. However, objective criteria to identify the two main lime-based painting techniques, fresco and lime-paint, have not yet been systematically verified on replicas. Replicas were painted following both fresco and lime-painting techniques. A comparison of microstratigraphic sequences and distribution of chemical elements reveals systematic differences between the two techniques, providing objective distinguishing criteria. Samples from the Abbey of Chiaravalle (Milan, Italy) and Pompeii were also analysed, and the results were compared with experimental data to validate the recommended criteria.

This comparative study of the paint and varnish coating histories of two early eighteenth-century chests and one court cupboard from Hadley, Massachusetts shows how they are related and how their brilliantly painted decorations have changed over time.  Optical microscopy was the primary tool for analysis, in combination with SEM-EDS analysis of selected cross-sections to identify the inorganic components in individual layers.

The painting materials of the Portrait of Nicolaes van Bambeeck (Royal Museums of Fine Arts of Belgium, Brussels, inv. 155) painted by Rembrandt van Rijn in 1641 has been studied using high resolution cluster-TOF-SIMS imaging. In the first step, a moderate spatial resolution (2 μm) was used to characterize the layer structure and the chemical composition of each layer on account of a high mass resolution. Then, in the second step, and despite a low mass resolution, the cluster primary ion beam was focused well below 1 μm in order to reveal smaller structures in the painting sample. The study confirmed the presence of starch in the second ground layer, which is quite surprising and, at least for Rembrandt paintings, has never been reported before. TOF-SIMS also indicated the presence of proteins, which, added to the size and shape of lake particles, suggests that it was manufactured from shearings (waste of textile manufacturing) of dyed wool, used as the source of the dyestuff. The analyses have also shown various lead carboxylates, being the products of the interaction between lead white and the oil of the binding medium. These findings considerably contribute to the understanding of Rembrandt's studio practice and thus demonstrate the importance and potential of cluster-TOF-SIMS imaging in the characterization on a submicrometer scale of artist painting materials.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging using cluster primary ion beams is used for the identification of a green painting layer on the scene The Angels concert from the Issenheim Altarpiece (painted in 1516) from a German Renaissance painter, Matthias Grünewald. Copper carboxylates clusters inside a basic copper chloride (atacamite) layer have been identified and located in the copper green layer. The mechanisms of transformation of atacamite into copper carboxylates may be initiated by an aging of the paint layers. The combination of the high mass resolution of the technique together with a micrometer spatial resolution and the possibility to simultaneously identify both minerals and organics has proved to be method of choice for the study of the stratigraphy of a paint cross-section.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging using cluster primary ion beams is used for the identification of a green painting layer on the scene The Angels Concert from the Issenheim Altarpiece (painted in 1516) from a German Renaissance painter, Matthias Grünewald. Copper carboxylate clusters inside a basic copper chloride (atacamite) layer have been identified and located in the copper green layer. The mechanisms of transformation of atacamite into copper carboxylates may be initiated by an aging of the paint layers. The combination of the high mass resolution of the technique together with a micrometer spatial resolution and the possibility to simultaneously identify both minerals and organics, has proven to be the method of choice for the study of the stratigraphy of a paint cross-section.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging using cluster primary ion beams is used for the identification of a green painting layer on the scene The Angels Concert from the Issenheim Altarpiece (painted in 1516) from a German Renaissance painter, Matthias Grünewald. Copper carboxylate clusters inside a basic copper chloride (atacamite) layer have been identified and located in the copper green layer. The mechanisms of transformation of atacamite into copper carboxylates may be initiated by an aging of the paint layers. The combination of the high mass resolution of the technique together with a micrometer spatial resolution and the possibility to simultaneously identify both minerals and organics, has proven to be the method of choice for the study of the stratigraphy of a paint cross-section.