DOI Page / Citation link:
https://doi.org/10.11588/diglit.42068#0094
MÉLANGES HULIN DE LOO
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thickness of ail the materials penetrated, including tke pic-
ture surface, the ground material, the panel or canvas, and
whatever has been added to the back of the picture—woo-
den supports or, occasionally, a coat of paint or wax. Since
brush strokes are in substance tiny variations in the tick-
ness of paint, they are usually well recorded on the x-ray
film, even when hidden from the eye by additional strokes
or glazes floated on to the surface of the picture.
It must be understood also that the range in density
between black and white pigment is as great as the range
in color value, but that the différence in density between
other colors — say red earth and green earth — is so light
as to be negligible. There is, in fact, such a confusion of
densities within a large range of colors, that, for ail prac-
tical purposes, the x-ray can be considered insensitive to
color values, outside the fundamental contrast between
lights (composed largely of lead) and darks (which hâve
only a smali metallic element). In some cases the x-ray
discloses the presence of mercury vermillion or a green
of high metallic content; and it usually records the old
dense ultramarine. But it is not so much the study of
color which interests one in x-ray work, as it is the brush-
marks—the draughtsmanship, the design, and the changes
which hidden brush strokes may reveal.
This is a curt explanation. But it is essential to our
understanding of the shadowgraph of Jan Van Eyck’s
Portrait of His Wife. Knowing that the x-ray records
ail the materials penetrated, we can recognize at once that
some of the cloudy aspect of the illustration must be
due to the fact that this panel is painted on both sides,
the two sets of shadows interfering with each other on
the film. But this alone, one judges after considérable
expérience with x-ray shadowgraphs (1), would not account
(1) The Fogg Muséum of Art, Harvard University, contains a file of
more than twelve hundred x-ray films, representing the work of artists
of ail periods, and obtained through the co-operation of Muséum authorities
in France, Germany, England, Belgium, Holland and America.
<37
thickness of ail the materials penetrated, including tke pic-
ture surface, the ground material, the panel or canvas, and
whatever has been added to the back of the picture—woo-
den supports or, occasionally, a coat of paint or wax. Since
brush strokes are in substance tiny variations in the tick-
ness of paint, they are usually well recorded on the x-ray
film, even when hidden from the eye by additional strokes
or glazes floated on to the surface of the picture.
It must be understood also that the range in density
between black and white pigment is as great as the range
in color value, but that the différence in density between
other colors — say red earth and green earth — is so light
as to be negligible. There is, in fact, such a confusion of
densities within a large range of colors, that, for ail prac-
tical purposes, the x-ray can be considered insensitive to
color values, outside the fundamental contrast between
lights (composed largely of lead) and darks (which hâve
only a smali metallic element). In some cases the x-ray
discloses the presence of mercury vermillion or a green
of high metallic content; and it usually records the old
dense ultramarine. But it is not so much the study of
color which interests one in x-ray work, as it is the brush-
marks—the draughtsmanship, the design, and the changes
which hidden brush strokes may reveal.
This is a curt explanation. But it is essential to our
understanding of the shadowgraph of Jan Van Eyck’s
Portrait of His Wife. Knowing that the x-ray records
ail the materials penetrated, we can recognize at once that
some of the cloudy aspect of the illustration must be
due to the fact that this panel is painted on both sides,
the two sets of shadows interfering with each other on
the film. But this alone, one judges after considérable
expérience with x-ray shadowgraphs (1), would not account
(1) The Fogg Muséum of Art, Harvard University, contains a file of
more than twelve hundred x-ray films, representing the work of artists
of ail periods, and obtained through the co-operation of Muséum authorities
in France, Germany, England, Belgium, Holland and America.