This document discusses how science can be used to analyze works of art to determine their authenticity, condition, age, and composition. It describes several scientific techniques, including illumination with different types of light, magnification, spectroscopy, x-rays, CAT scans, and radiometric dating. These techniques provide information about the object's surface, internal structure, materials, and age. While scientific analysis is useful, it must be considered alongside connoisseurship opinions and may require invasive testing that risks damage.

1. EXCERPTED FROM:
An Approach To Advance Problem In Appraising
Art, New York: 2011
Science: The Tests Available For Understanding
The Condition And Authenticty Of Works Of Art
By Dr Michael Cohn
Science today is an integral part of art restoration and conservation as
well as frequently used in art authentication. While appraisers are not
authenticators or art restorers, the authenticity and condition affect the
value of works of art. Thus scientific evidence of authenticity and
condition will be factored in ones appraisal and reporting. Science is
often sidestepped because of many individuals focus on aesthetics and
intimidation of the technical scientific terms. However, it is often not
necessary to understand chemical equations and radioactive
decomposition to recognize essential scientific information about a work
of art.
For scientific analysis of art and antique, the object qualities may be
broken down into three areas of information to be gained: information
about the age of the object, information about the composition of the
object and information about the form or structure of the object. Each
area has scientific tests that are able to yield specific reproducible
information about the piece. While there are issues around the use of
these tests such as the invasiveness and destructiveness of the particular
test, there is less worry about their reliability. Of course, each object
must be considered individually and connoisseurs and specialists
opinions are as always very important concerns

2. Illumination and magnification are very useful.
Illumination can be used in several forms and in different ways to extract
information about works of art. While one might think, looking at an
object under bright light is all that is available; there are actually many
procedures to be used. The generally forms of illumination are visible
light, which is the wavelength spectrum which is seen by the normal
naked eye, and ultraviolet and infrared which are outside the ability of the
naked eye. Also, polarized light may be used. This is especially used in a
microscopic technique. Finally, fiber optic lights with long focal lengths
allow us to observe hard to reach places. These illuminations also may be
combined with techniques such as microscopy, spectroscopy and
photography to enhance the ability to gain information.
Visible light may be used in different ways. It may be used as spectral
illumination, raking light or transmitted light. The spectral illumination is
aimed directly or spectrally at objects. This way shows us the object’s
color, shape and size, and reveals the presence of surface coatings or
gloss. Raking light passes across the surface of the object and often
reveals media techniques and texture as well as damages to the surface.
Transmitted light is set up, to penetrate when possible, through the
object. This method can show many characteristics such as variations in
densities of objects. With paper and translucent works of art such
characteristics as watermarks as well as tears or repairs are observed.
Ultraviolet light, or "black light", reveals changes in elemental
composition on the surface of objects because it causes specific
fluorescence in materials depending on composition and age. While the
ultraviolet light is not directly seen, the changes that occur when utilized
allow this observation. Retouching, overprinting, varnishes, adhesives,
and certain types of deterioration that might be invisible to the naked
eye, like mold damage, can be detected
Infrared (IR) radiation is electromagnetic radiation of a wavelength
longer than visible light, but shorter than microwave radiation. This
method can reveal carbon containing materials and otherwise "invisible"
medium. Carbon media hidden under retouching, dirt, or other media can
be seen, revealing under drawings or changes in to original drawing. It
can reveal covered signatures, or erased pencil and ink, or abraded or
faded drawings. It can even penetrate paint layers to show primatura, or
preliminary drawings.
Fiber optics allow one to reach places that are inaccessible to the eye
Magnification: In addition to illumination, magnification is a useful and
relatively simple means of examining an object. Magnification

3. techniques can vary from a simple hand held magnifying glass or loupe
to a scanning electron microscope.
Magnifying glass can often help to identify inclusions in paper or the
type of media. However, sometimes much higher magnification is
required. It can enlarge many marks to identify signature. It can enlarge
areas to reveal discrepancy in surface treatment condition, cracks and
encrustations.
Microscopes are adequate for much scientific analysis of works of art.
Not all questions of scientific analysis require complex analytical methods
there are several types of microscopes in use.
General Microscope, the more commonly used one, is light illuminated.
The image seen with this type of microscope is two-dimensional. It has
high magnification, but a low resolution. In the case of bronzes, the form
of the finished artifact, together with surface traces left by flaws in the
casting and final working by the bronze smith, usually reveals the
production method. The metallographic examination under a microscope
can clarify the kind of mould used (metal, stone or clay) and distinguish
between cold-worked and cast objects. When this microscope is
combined with a stage for placing the object, samples may be magnified
with more easy and ability to study. When additional combined with
polarized light, it may be magnified more than 100 times. This type of
microscope can aid in the identification of an unknown component not
only by magnifying its features, but also by allowing measurement of the
optical properties of crystals, such as refractive index, extinction, and
birefringence. Carefully selected samples may provide information,
which is not only approximately qualitative (i.e. what is present), but also
quantitative (i.e. how much is present). This technique permits the
identification of pigments and fibers.
Stereoscopic microscope is light illuminated and the image that appears
is three-dimensional. Stereoscopic microscopes may be equipped with
cool temperature fiber optic raking light and ring. This technique can
clarify the nature of media by revealing the size and shape of particles,
the location, the layers of media or coatings, the extent of damage,
retouching or repairs.
Scanning Electron Microscope (SEM) use electron illumination and the
image is seen in three dimensions. It has high magnification, high
resolution and a great depth field. It can reveal morphological and
topographical characteristics of the piece.

4. Transmission Electron Microscope (TEM) also uses electron
illumination; however, the image is a two dimensional view. Thin slices of
the work are needed: this can be a destructive technique.
Solvent test is used to expose layers for observation and thus can
expose covered inauthentic joints. Also, if a layer responses to solvent it
is NOT a fired ceramic. However, this test is invasive and destructive to
the part of the object tested and therefore must be justified before its
use.
Photography utilizing infrared and ultraviolet light and film allows
under painting, under drawing, and other markings invisible to the naked
eye to be imaged.
Information about the form or structure of an object is revealed by X-rays
and CAT scans. As you can imagine, knowing what is inside an object,
what is below the surface can aid greatly in knowing how to restore and
conserve the work of art as well as indicate technical inconsistency with
the period of the piece or with its usual method of fabrication.
X-Rays or X-radiography is a two-dimensional imaging technique,
utilizing a stream of photons that pass through the object creating an
image of what is inside. It reveals the form and content of what is below
the surface.
Gamma Rays or Gamma radiography is a similar technique but is more
powerful than x-ray and can penetrate stone and enables one to see
layers under surface of these more dense materials.
CAT or Computed axial tomography (CAT) scan is a technique
borrowed from medical disciplines and is used to get a very accurate
three-dimensional X-ray of objects ranging from wood and marble to
terracotta. Basically, an X-ray tube is directly or indirectly rotated around
the object at different angles under the control of a computer to produce
this cross-sectional or three-dimensional picture.
For age the Radiometric Dating tests are very helpful. Basically by
measuring the decomposition of a radioactive substance that is integral
to the piece, one can determine the age of a work. While there are several
radioactive tests, the one most frequently used and that you will
encounter is the Carbon Dating test. This test uses the naturally
occurring isotope of carbon-14 to determine the age of organic materials
such as wood, cotton and wool, up to ca. 50,000 years. Thus objects
such as ones made directly from wood or paintings done on wood may
have the wood’s age measured to see if it corresponds to the proposed

5. age of the piece. However, as a caveat, a new painting may be painted on
old wood
Again for age there is Dendrochronology. This is the science of studying
growth rings in trees to ascertain their age and thus the age of the wood
used in the art object
The TL or Thermoluminesence test is a scientific method of determining
the age by establishing when it was last fired. Thus, this test is
appropriate for ceramics such as earthenware and low-fired stoneware,
high-fired stoneware and porcelain and for cores of fired objects such as
bronzes.
Furthermore, one may use anachronisms yielded from other scientific
tests such as X-rays and chemical analysis used for form and
composition that indicate materials found in the work that were not
available in its period or under painting of scenes figures that post dated
the supposed age of work under examination.
Chemical analysis can offer information about the composition of a
work of art. Understanding the composition of a work of art or antique
will enable one, as mentioned, to find consistency with known genuine
works or materials that were not usually found. This is a form of
conformation of authenticity. Spectrometry and chromatography are two
general scientific test areas that reveal quite precise information about
the chemical make up.
Composition or the materials that make up the work under consideration
have many scientific tests available to determine these materials.
Pigments and stains, binders and glues, nails and rods, stretchers and
boards, the chemicals, atoms, compounds and minerals may be
measured for presence and quantity.
Analytical chemistry is the analysis of material samples to gain an
understanding of their chemical composition and structure.
Spectroscopy is the use of identifying the unique spectrum or of a
substance. It is often used in physical and analytical chemistry for the
identification of substances, through the spectrum emitted or absorbed.
A device for recording a spectrum is a spectrometer. Thus, spectroscopy
can be classified into absorption or emission spectroscopy. Absorption
spectroscopy uses the range of electromagnetic spectra, which a
substance absorbs, and emission spectroscopy uses the range of
electromagnetic spectra, which a substance radiates. There is different
originating electromagnetic frequencies including light, infrared and

6. ultraviolet used to pass through a material to be analyzed. While there is
a form of spectroscopy that requires the material to be vaporized and
thus destroyed in order to analyze, there are UV (ultraviolet, IR (infrared)
frequencies that may pass through liquid or dried samples to determine
the molecular components including structural information. Which may
(FTIR microscopy combines two analytical tools: a microscope and an
infrared spectrometer. The infrared spectrometer is a high-tech
electronic machine that measures infrared light that passes through or
off a sample. The microscope is an accessory used to position an
exceedingly small specimen in the light path. The technique produces a
spectrum of peaks that is used to identify many thousands of materials,
from drugs to explosives to pigments.
X-ray fluorescence spectroscopy is when X-rays of sufficient frequency
(energy) interact with a substance to be tested and analyzed. The inner
shell electrons in the atom are excited to outer empty orbital, or they may
be removed completely, ionizing the atom. The inner shell "hole" will then
be filled by electrons from outer orbital. The energy available in this de-
excitation process is emitted as radiation (fluorescence), which is a form
of emission spectroscopy, or it will remove other less-bound electrons
from the atom known as the Auger effect. The absorption or emission
frequencies (energies) are characteristic of the specific atom. In addition,
for a specific atom, small frequency (energy) variations occur which are
characteristic of the chemical bonding. With a suitable apparatus, these
characteristic X-ray frequencies or Auger electron energies can be
measured. X-ray absorption and emission spectroscopy thus are used to
determine elemental composition and chemical bonding.
Fournier transmission Infrared Spectrometry (FTIR) enabled the
ground layer to be analyzed. Here the spectra from this thanka indicated
a protein and a higher than expected binder-to-pigment ratio than other
early thankas. The earlier thankas are thinly bound with a lower binder-
to-pigment ratio. In this case, the results are believed to represent
substantial restoration or conservation treatments rather than the
paint medium
Electron Probe Microanalysis EPMA is based on x-ray fluorescence (that
is emission as opposed to absorption. Basically it works by bombarding a
micro-volume of a sample with a focused electron beam and collecting
the X-ray photons thereby induced and emitted by the various elemental
species. Because the wavelengths of these X-rays are characteristic of the
emitting species, the sample composition can be easily identified by
recording

7. Pigments or Paints are certainly an area that we are familiar with.
Analyses of these pigments are essential in fine restoration and
conservation but also provide supporting or disputing information
concerning a work of art. Here the above spectroscopy allows specific
identification of many of the substances that make up the colors.
New techniques:
Dimensional Interplay Analysis or Fractual Analysis is a technique
that detects characteristic patterns in a work of art. This can be applied
to artists in their paintings. Fractal geometry, which repeat themselves, or
fractal patterns may be revealed from a seemingly chaotic appearance at
different magnifications. By using computers to identify a highly specific
and identifiable form of this fractal patterning, a profile or what you may
call a fingerprint or “signature” associated with a specific artist may be
established. As an example, a recent group of disputed Jackson Pollock’s
poured paintings were examined by R.P Taylor, the initial developer of
this technique. Here, Taylor placed computer-generated grids over
photographs of the works, and found two distinct sets of fractal patterns.
One was on a scale larger than 5 cm; the other showed up on scales
between 1 mm and 5 cm. These signature patterns may be attributed to
such factors as the artist’s body motion, his height over the canvas, the
angle and force behind the trajectory of the paint that are qualities of the
artist. Other poured paintings not by Pollock did not demonstrate fractal
patterns that the Pollock paintings shared. Although there may be some
variations in patterns between paintings and the need for caution, this
technique is useful when coupled with other important information such
as provenance, connoisseurship and materials analysis.
DNA Analysis uses DNA tests to identify hair and other personal body
elements found in works of art. When the DNA fingerprint of a artist is
established, other sources of DNA embedded in works of art and that
may be clearly associated with that work of art, may enable a connection
to be established between the artist and the work of art under
investigation.
Science has offered us an arsenal of techniques to further look into a
work of art. It helps answer such questions as when was it made, was it
altered, what are the materials that compose it, what are the weaknesses
in its structure as well as a host of other concerns. These are certainly
concerns for the value and the maintenance of these works.
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