Rocznik Muzeum Narodowego w Warszawie (3(39).2014)

Grażyna Bastek et al. Technological Examination of the Warsaw and Boston Versions...

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The first sample from the Boston painting (BOSi) comes from the left edge of the work
- of a fringe wound over the stretcher. The other one (BOS2) was also taken from the fringe
at the height of the middle of the composition, on the left as well. When the samples were
being collected, a dark layer was found, probably a secondary one, added upon transfer after
removing the original ground.31
In the cross-section of BOSi three layers can be seen (fig. 21). The upper one is light grey;
the middle one is white-blue with blue crystals whose morphology is similar to azurite. In
UV light both layers show mediocre yellow fluorescence, which - similarly to the Warsaw
version - implies the use of oil as a binding medium.32 The lower layer is dark blue - lack of
fluorescence suggests that it may contain aluminosilicates, such as clay. Between the white-
blue and dark blue layer there is a local red layer (most probably it is a sealing substance also
coming from the transfer).
In the upper part of the cross-section of BOS2 (fig. 22a) one can see a light grey layer, and
in the lower part - a dark blue one. The compositions of each of the samples from the Boston
painting are alike, though in BOS2 more white is contained. Below the light grey layer there
is a double layer consisting of an intensely green finish and a light green underpainting with
numerous grains of light green morphologically more similar to verdigris or copper resinate
than to malachite. Upon UV illumination a distinct yellowish fluorescence appears only in
the upper, light grey layer. Between the two lower layers (the dark green and the dark blue
one) stands out another, very thin layer of a noticeable fluorescence (fig. 22b). It may be a
remnant of some original imprimitura, although it was not found in BOSi sample. Both, in
turn, have that local red layer, that must have been a sealing substance used during the transfer.
The next step on the way to identification of painting materials in cross-sections was the
analysis using scanning electron microscopy with EDS (SEM-EDS).33 The measurements
were taken in 2013 at the Faculty of Chemistry, University of Wroclaw, using a Hitachi S-3400N
scanning electron microscope with an EDS Thermo Scientific Ultra Dry detector. All of the
measurements were performed at low vacuum with an energy of 30 kV and magnifications
of the order from 120 to 20,000 times. For each cross-section their elemental compositions
was examined in over a dozen single points measurements and was mapped.34 An important
advantage of this technique is the possibility to determine the distribution of elements in the
sample, which is of particular significance when analysing cross-sections.35
SEM-EDS examination of WAWi and WAW2 samples confirmed the previous conclusions
based on stratigraphic analysis. Single point measurements, as well as mapping the surface of
WAWi, showed that in the lower layer (ground) there is calcium, sulphur and oxygen, indicating
the presence of calcium sulphate - possibly gypsum (fig. 23). Raphael and his studio utilized
gesso made of gypsum mixed with animal glue vigorously stirred and heated, which produced

31 See “Transfer of the Painting Layers of the Boston Holy Family” - pp. 183-86 above.
32 The research carried out in the Cultural Heritage Research Laboratory, Faculty of Chemistry, University
of Wrocław, with GC-MS confirm that oil binding medium was used.
33 Stuart, op. cit., pp. 91-93 and 234-38.
34 Examination performed in the Cultural Heritage Research Laboratory, Department of Chemistry,
University of Wrocław.
35 Ciba, Kozieł, Łydżba-Kopczyńska, op. cit., pp. 42-43.