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By studying an artwork with a stereomicroscope,
researchers obtain a wealth of information few other
methods could match. |
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Fragment of paint layer under a microscope
(magnified x 40). |
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Photographs of a detail from the painting Portrait of N.S. Borshchova by Dmitry Levitsky,
taken under regular lighting (left) and under UV
rays (right). The UV photo shows the thickness of
the yellowed varnish and exposes multiple later
additions of paint on top of the varnish (the dark
spots). |
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Detail from
X-radiograph of Ivan Nikitin's Portrait of
Unknown Men. |
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The Russian Museum’s biological and chemical
research lab |
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Micro-sample of a
fragment taken from a section of an artwork, under a
microscope (magnified x 200).
Source |
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First, a museum piece is
studied under a
stereomicroscope. Generating more information than most other research methods,
the stereomicroscopic method is unmatched in accuracy when it comes
to assessing an artwork’s integrity. It is the best method for
exposing the extent of previous restorative interventions and,
specifically, identifying older added touches of paint that were
concealed under more recent coats of varnish, which UV testing often
fails to recognize. Microscope-assisted research offers, for
example, the only way to identify old restorative toning and any
overpainting that, although dissimilar to the original paintwork in
the composition of the coloring agents, the degree of transparency,
and the texture, have over time become almost indistinguishable from
the original work as regards transparency, are very close in color
and, on occasion, have also developed the same crack patterns as the
original painting. Microscope studies make it possible to identify
the original color scheme of an artwork by analyzing the remaining
original paintwork.
Second in importance is
an examination of the front surface in
UV
light. UV
rays will either reveal the cumulative light emission of the protective
coats of varnish, the paintwork, and the primer, or the emission of each
component separately in those parts where the primer or the paintwork are
exposed. This provides valuable data on the integrity of the artwork
(identifying missing paintwork and primer) and assesses the depth of later
retouching in relation to the protective coats of varnish.
The findings of a UV
study can be double-checked through microscopic analysis, while the pigments
identified by the UV rays can be parsed by analyzing the chemical
composition of micro-samples. When an artwork is subjected to UV radiation,
the key features of the visible emissions to examine are the brightness,
color, density, and uniformity of the painted surface, and whether there are
any dark areas indicating instances of previous restorative intervention,
pollution, or uneven application (or complete absence) of a protective coat
of varnish.
Another key component in
a technological study,
X-ray (radiography) of the surface provides an additional opportunity to
assess the integrity of an artwork, as it identifies certain irregularities
that evade the naked eye: breaks in and losses of the base, paintwork, and
primer; subsequent restorative interventions; evidence of transfer to a new
base; etc. It will also help to identify some of the materials used in the
painting. When analyzing the X-ray, the experts look at such critical
qualitative characteristics as the readability of the image, the contrast of
the light and shade pattern, and the detectability and shape of individual
brushstrokes. Image readability is determined by the nature of the base, the
composition of the primer and the paint, the thickness and number of coats
of primer and paint, the
techniques used to create forms and the types of paintbrushes used, and the presence or absence
of prior restorative interventions.
X-ray fluorescence
(XRF) analysis is a spectroscopic analysis method that has been
widely used in recent years to identify the elemental composition of
various substances. XRF is good for analyzing the composition of
paintwork (including pigments) and primer. The XRF method collects
and analyzes the spectrum obtained by irradiating the object of
study with X-rays. The RFA method is easy, quick, accurate and
requires no complicated sample preparation, so it’s no wonder that
its application in the analysis of visual artworks is constantly
expanding.
A biological and chemical study of a work of visual art is primarily aimed
at gaining a comprehensive understanding of the composition and properties
of the materials from which the piece was created. These studies allow the
conservator to determine more or less exactly where the boundary lies
between the authentic elements of a piece of art (i.e., those done by the
artist) and later additions, and how to choose the right solvents to
reinforce its structure. The optimal strategy and tactics for preservation
can be determined based on the results of these studies. The spectrum of
materials studied is quite wide, and includes paper, textiles, wood, stone,
metal, minerals, and the organic substances that make up paint. Therefore
the methods used also vary widely.
A common approach
is to study the stratigraphy and thickness of the paint layers, their
transparency, and their components in thin sections of microscopic samples
of material under transmitted polarized light, which can be magnified up to
1000 times.
We also study biological
damage that has been done -- which can potentially cause an artwork
irreparable harm -- and then determine the best method of fighting it.
The study and analysis
of fine artwork is done by members of the technological research team and
biological and chemical research team, part of the Russian Museum’s Art
Conservation Department.
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