Historical Painting Techniques, Materials, and Studio Practice

3Na20·3Al203·6Si02·2Na2S; vivianite Fe3 + 2(P04)2·SH20; cinnab:l.r, HgS;
red lake; red lead, Pb304; hematite, Fe203; green earth,
K[(Al,Fe"')·(Fe",Mg)]· (AlSi3,Si4)O,o (OH)2; yellow iron oxide, Fe203·H20;
and lime white, CaC03.
One of the most interesting findings is that red lake was used for the unusual
pink color of Nicodemus's robe. This is the earliest identification of this
pigment in English wall painting, though at Miistair (Switzerland) a red lake
pigment thought to be madder has been identified in the Carolinian scheme
of circa SOO (11).
The inclusion of vivianite in the palette is particularly surprising, not only
since this pigment has not previously been identified in English medieval wall
painting, but also because it was clearly selected fo r its distinctive coloristic
qualities rather than as an economic alternative to other mineral blues (12).
The characteristic deep indigo blue of vivianite, set against a pale blue of
natural ultramarine combined with lime white, was employed for the central
details on the vair (bluish gray and white squirrel fur) lining of Nicodemus's
cloak in the Deposition. Although the iron phosphate mineral has now altered
and appears green, an examination of the Morgan leaf from the Winchester
Bible (ca. 11 70-1 1 SO) shows that vair linings were represented by pale blue
elements with a dark blue center, and it is clear that this was also the intention
in the wall paintings.
Binding media. Analysis undertaken initially by microchemical tests on thin
sections and cross sections was followed in some cases by Fourier transform
infrared microspectroscopy. Results confirmed that although the carbonation
of lime is the principal binding mechanism, a proteinaceous component is
also present in some samples. A proteinaceous component was identified, for
example, in a paint layer consisting of red lead, lead white, and calcium carbonate
in Sample 27, taken from the impasto decoration of the geometric
border. Likewise, a proteinaceous component was identified in a layer of calcium
carbonate applied beneath a resinous mordant for gold leaf in Sample
30, from the halo of the angel in the Entombment.
Instrumental analysis of the media of comparable wall paintings is rare, but it
is significant that, where available, it indicates similar findings. For instance,
in the paintings (ca. 1130) of Idensen (Lower Saxony), the presence of a
proteinaceous binding medium is associated with blue and green pigments,
while in the scheme (ca. 1130) in St. Gabriel's Chapel, Canterbury Cathedral,
both linseed oil and protein have recently been identified as part of the
original technique (13, 14).
Application. The presence of a sinopia, and the application of the into naco in
overlapping patches, indicate that the primary binding mechanism for the
pigments was the carbonation of calcium hydroxide from the lime plaster;
that is, at least the preliminary drawing and initial pigment layers were applied
a fresco. However, the stratigraphy of the final painting is remarkably complex
and varies substantially across the pictorial surface, from thin single layers
applied directly on the lime plaster substrate to paint applied in considerable
impasto, often over colored grounds (Table 1). In Sample 24, a single layer,
just 30 f.Lm thick, of yellow iron oxide combined with umber and a few
charcoal black particles has been applied directly to the white plaster substrate.
Layers such as this are likely to have been applied a fresco. For areas of flesh
painting, multiple layers have been applied to produce complex effects of
modeling. In Sample 7, the mid-dark flesh tone has been produced by the
application of five different layers of earth pigments-green, red, and yellowapplied
either singly or in combination, often with the addition of lime white
and charcoal black. Here, carbonation of the lime white pigment provides
additional binding capacity within the complex layer structure. By contrast,
red lead combined with an additional proteinaceous binding medium was
applied in a layer some 200 f.Lm thick for the decorative motifs on the central
border, over a thin layer of carbon black applied directly to the lime plaster.
96
Historical Painting Techniques, Materials, and Studio Practice