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there is a lead-white underpaint or imprimatura. X-radiographs of the central
panel show a similar vigorous, striated, and randomly applied layer in some
areas.The relationship between the underdrawing and the final image. In the main and
predella panels, the layers of paint fo llow the outlines of the underdrawing in
a general fashion. There are many major and minor departures from the
underdrawn outlines, however, and additional elements have been added to
the composition in the paint stage without any redrawing. There are nu
merous examples in the predel1a panels. For example, in St. Nicholas Slips a
Purse through the Window if an Impoverished Nobleman, the hand and purse
were painted slightly lower than they are drawn, and a shoe and stocking that
were not included in the underdrawing appear. The praying hands of the
fo remost boy in St. Nicholas Restores Three Dismembered Ch£ldren to Life were
lowered in the paint stage and St. Nicholas's crosier was raised in the same
scene.In the side panels, St. Anthony's fo reground fo ot is drawn in a lower position
than it was painted. The elaborate gold crosier that St. Nicholas grasps is
changed from the drawn to the painted version. These changes were made
at the initial stage of painting without any redrawing.
In the central panel, there are fewer changes from the underdrawing to the
final image, however, the Virgin's head was painted higher than it was drawn.
The X-radiograph shows this change was made after the first layer of St.
Anne's wimple had been laid down, after which the head was painted in its
new position, without any detectable redrawing.
The pigments and layer structure. The painting technique of the center panel of
the altarpiece is similar to that fo und in the Ghent altarpiece (17). There is
evidence fo r an oil-based sealing layer toned with red and black pigments
over the underdrawing and under the paint. The paint structure is multilay
ered and the colors are worked from light to dark. The cross sections show
that each large area of color was blocked in using a light tone of the final
color. For example, the Virgin's mantle is underpainted in pale blue (Plate
29d); a blue-green layer blocked in the whole area of the cloth of honor
(Plate 2ge); and the throne, on which statues of putti stand, is underpainted
with a lighter gray (Plate 29a) (18). Type III underdrawing provides the mid
tone in St. Anne's drapery, which was painted using two layers of vermilion
and red lake covered by multiple layers of a transparent red glaze (Plate 29b).
The paint layer structure in the side panels is not the same as in the center;
the build-up of color and fo rm is quite different. St. Anthony's robe has only
a single violet-gray layer (Plate 29f). St. Nicholas's chasuble was painted by
laying in a yellow ochre base, on which shadows were created with a thick
dark layer of black pigment mixed with vermilion. Whereas in the center
panel the layers of paint are always tonally related (e.g., red covering red), in
St. Nicholas yellow paint is used as a base fo r red and green in the saint's
vestments. In the red embroidered chasuble, the cut velvet was painted with
a layer of vermilion mixed with red lake. Red glazes were applied to depict
the texture.
The technique of Lamentation at the Foot if the Cross, as described by Butler,
is similar to the technique employed on the predel1a panels in the use of an
imprimatura containing lead white and in the relatively simple layer structure
(19). Certain similarities to David's The Virgin and Child with Saints and a
Donor are seen in the paint structure (20).SummaryThe central fi gural group of the center panel was produced using a different
technique from the rest of the altarpiece. Its structure is similar to those fo und
in earlier fifteenth-century paintings, such as in the Ghent altarpiece (21).
This method of working-sealing the underdrawing, laying in light tones,Historical Painting Tech niques, Materials, and Studio Practice