A painting can be accurately
authenticated through a combination of forensic and
stylistic analysis (or Morellian analysis).
Entire volumes have been produced on the intricacies of
forensic analysis of painting, therefore this chapter
offers only an outline of the remarkable scientific
tools available and the ways they can be combined with
Morellian disciplines to authenticate paintings.
Forensic science studies anomalies in the chemical and
physical composition of a painting. It examines the
paint's ingredients, the chemical makeup of the canvas
or panel, and markings that lie below the paint surface.
Analysing such anomalies is critical to gaining an
understanding of a painting's composition, origin, and
age.
Science approaches the study of art opposite to the way
that a connoisseur would. While the connoisseur
generally tries to expand the opus of artwork, forensics
aims to exclude forgeries. Forensic science takes a sort
of "guilty until innocent approach" to art research
whereby a work is not considered authentic until its
attributes conform to set standards.
Forensic science can examine the entire contents of a
painting, including its chemical composition and the age
of the canvass or panel, the chemical makeup of its
paint, and the ingredients used to bind the paint. For
example, a scientist may uncover a forged 16th century
Titian painting if it includes zinc-white paint that had
not been introduced until 1780.
Generally speaking, there are two types of forensic
analysis. The first type involves photographic
techniques that use infrared, x-ray, and ultraviolet
light. This is the most common form of scientific test,
although its major weakness lies in the fact that it
does not study samples extracted from the painting.
Infrared Reflectograpgy identifies markings or drawings
that lie underneath the paint surface. In the old
masters, under-drawings were often drawn directly on the
canvas as a kind of plan for the painting. Examining
under-drawings can help to establish a painting's
authenticity and can be compared against the artist's
style. Infrared radiation can also detect authentic
signatures that are indistinguishable to the naked eye,
or can reveal fake signatures that were added years
after the completion of a forged painting.
X-ray photography uses short-wave radiation to detect
alterations in a painting. It can also indicate the
types of paints it contains. X-rays will identify areas
of a painting that have been repaired or changed. For
example, x-rays could reveal a forged signature added
after the initial painting was produced. This method
also identifies certain types of x-ray absorbing
pigments, including lead white and led-tin yellow.
Since historians have determined when these paints were
introduced, their presence can shed light on the
painting's time of execution. These techniques can be
coupled with UV light analysis to reveal areas of
inpainting that can sometimes aid in the identification
of pigments.
While x-ray, infrared and UV photography are essential
research tools, they must be employed in tangent with
additional tests to properly assess a painting. For
example x-ray photography, while capable of detecting
lead-based paints, cannot quantify the paint's precise
lead content. In addition, these technologies are
incapable of analysing organic material-such as
organic binding ingredients in paints.
Investigating a painting through photographic
examination alone - without combining it with other
forensic and Morellian tests, can produce highly
deceptive results. An analyst may proclaim that x-ray
photography has proven the existence of lead-white paint
and that the painting is therefore a Venetian
Renaissance work. Such an assessment would ignore the
fact that photography is incapable of determining
whether the lead content is consistent with the period
of the work. An adequate forensic examination must
include the study of samples from the painting.
The second and more effective category of scientific
testing involves the extraction and analysis of samples
from a painting. The most advanced method is Reflection
x-Ray Fluorescence Spectrometry Analysis (TXRF), which
uses x-rays to examine pigments taken from a painting.
The extraction process involves obtaining a micro-sample
by brushing a cotton swab over the surface of a
painting, causing no damage to the work. The sample is
then placed on a glass plate and subjected to
high-intensity x-Ray radiation. This stimulates the
chemicals in the sample and causes them to release
secondary x-ray signals. Each element in the sample
emits a unique x-ray signature, allowing one to
determine the precise elemental contents of the sample.
According to scientists R. Klockenkamper et al, "a
characterisation of the pigments may help in assigning a
probable date...to the painting." This is because each
type of paint has a unique chemical composition that is
traceable to the time it was introduced. For example,
Prussian Blue, which has a chemical composition of
Fe4(Fe(CN)6)3, was not used by painters until 1725.
Therefore, if a painting attributed to Rembrandt
contains Prussian Blue, it can be immediately dismissed
as a forgery.
TXRF examination differs from simple x-ray, UV and
infrared photography because it involves the analysis of
actual paint samples rather than non-intrusive
photography. It is thus capable of producing a detailed
forensic chemical report on a painting that is far
beyond the means of photography.
There are also more intrusive forensic analysis
techniques that require paint samples (i.e. small chips
of paint). These methods are very effective, but are
considered unacceptable to many galleries because they
cause a small amount of damage to a work. One such test
is the Atomic Absorption Spectrophotometry (AAS) and
Inductively-coupled Plasma Spectrometry (ICPS) tests.
These are used to detect chemical anomalies in a
painting and/or materials that do not conform to the
standards of the time and place of a painting. AAS and
ICPS are conducted by burning a small amount of paint
and studying its resin. As with the TXRF test, the AAS
and ICPS method analyses trace elements in paint and can
determine whether the paint was produced after work was
supposed to have been made.
Other tests include the study of carbon-based binders
such as oil and glue used in paint media, which can be
dated according to their carbon-14 content -- much used
in other fields such as archaeology. Scientists have
also developed a new method capable of accurately
determining the age of the paint film itself. This was
previously impossible via the standard carbon testing
method, due to the many impurities in the paint.
Another important but intrusive dating method called
Radiocarbon Dating goes beyond the short two hundred
fifty-year range of the lead-isotope test. The technique
can date pictographs made from paints containing a wide
range of organic binders: blood, urine, honey, and many
other natural substances used .to bind together
pigments. The new technique.separate[s] the paint's
organic component from inorganic contaminants that
distort the age reading.. To isolate the organic source
of carbon, the scientist treats the specimen with
oxygen-based plasma. It combines only with the organic
carbon in the paint since the carbon in the [inorganic]
rock is already in a fully oxidized stable state. The
reaction of the plasma and the organic carbon produces
gaseous carbon dioxide, which is collected as dry ice,
and dated by well-established accelerator mass
spectrometer method that compares the number of
radioactive carbon isotopes and the stable carbon
isotopes in the sample. In the first trial the technique
found the painted pictograph fragments to be 3865 years
old (plus or minus 100 years).
Scientists can cross-reference these tests with DNA
analysis of organic matter used in painting, from nut
oils, brush hairs, canvas fibers and egg yolk -- tracing
these components to their places of origin.
Dendrochronology, the science of dating wood, can
determine the age of some panel supports.
There are many more scientific techniques tests
available that have not been detailed here. More
detailed descriptions of these techniques are provided
in The Scientific Detection of Forgeries (1975) by S. J.
Fleming.
Morellian Analysis
To comprehensively analyse a painting, a forensic
examination should be accompanied by a stylistic study
using Morellian techniques. Morellianism is an
empirically based method of separating false and genuine
artwork that was developed in the late nineteenth
century by physician and art collector Giovanni Morelli.
Morelli's method for attribution seeks to distinguish
individual artists and workshops by idiosyncrasies or
repeated stylistic details that arise in their works.
Morelli recognised that an artist, upon reaching a level
of proficiency, develops formulas in the creation of
figures, which maintain consistency and are sustained
throughout his life, even as his style evolves. Through
close study of these repeated details, formulas are
identified and mapped, allowing the observer to readily
identify evidence of the hand of a particular painter in
a work, like a detective matching fingerprints. The
evidence lies in the workmanship of both large and small
brushstrokes, the artist's application of paints to
create features such as eyes, collars or plants. The
painting's features are then matched with the unique
formulas by which the painter is known. Morellian
analysis can be compared to handwriting analysis, which
is accepted as evidence in law courts.
Although Morellianism is sometimes called a scientific
technique, it relies to some degree on the experience of
the analyst.
By combining the previously described set of scientific
tests with Morellian analysis, one can produce a highly
accurate assessment of a painting's authenticity. With
forensic research, one can determine the age, origin,
composition and materials of a work. Forensics can
identify the region from which paints derived, the
studio where a painting was made, and any alterations
that occurred after the painting's completion. A skilled
Morellian scholar (or preferably, a group of Morellian
scholars) can then assess the stylistic intricacies of
the painting and workshop to which it is attributed.
Perhaps the most successful implementation of Morellian
and scientific analysis was with the Rembrandt Research
Project (RRP). It is necessary to provide some
background on this groundbreaking committee.
The RRP was first proposed by art historian Bob Haak,
who was involved in preparing the 1956 Rembrandt
exhibition at Holland's Rijksmuseum to commemorate the
artist's 350th birthday. Haak was troubled by the sheer
number of works attributed to Rembrandt, and encountered
immense difficulty arranging them chronologically. He
concluded that many of these supposed Rembrandts must be
fake.
Art Historian Gary Schwartz quotes Haakas stating, "One
man could have not created so many different sorts of
pictures at one time." Haak teamed up with four other
art historians, with the committee led by Joos Bruyn, an
Art History Professor at the University of Amsterdam.
The RRP set out to independently review the body of
alleged Rembrandt paintings with Dutch government
funding provided in 1968.
The scope of the RRP's research has been immense. Since
its inception, the Committee has produced three volumes
documenting seventeen years of Rembrandt's career and
the some nine hundred Rembrandt works throughout the
world. So far, the Committee's rigorous efforts have
re-attributed six hundred 'Rembrandts'. One of
Rembrandt's most famous paintings: The Man With a Gilt
Helmet in the Berlin museum - was declared a forgery
after forensic and Morellian examination. The painting
is perhaps one of the most reproduced paintings in the
last two hundred years. After the Rembrandt Committee
assessed this painting, it was designated an
eighteenth-century fake.
Also withdrawn were the Polish Horseman, in the Frick
Collection, The Man with a red Bonnet in the Museum of
Rotterdam, The Portrait of Cornelia Pronck in the Louvre
Museum, and the Good Samaritan in the Wallace Collection
in London. Embarrassingly, The Portrait of Rembrandt's
Mother in the collection of the Queen of England was
also declared a fake (so much for the all-important
provenance).
Without forensic or Morellian verification, a painting
cannot be considered authentic.
