Uncovering Art Forgery Using Analytical Chemistry

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Uncovering Art Forgery Using Analytical Chemistry
Patricia Munter University of Pennsylvania MCEP
2008
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Art and Science Meet

• Many museums house laboratories for materials
  analysis
• Mainly for restoration and conservation
• Sometimes materials analysis can authenticate a
  work
• How can science support the preservation of our
  cultural history?

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Real or Fake
FAKE
Yesterday this picture was worth millions of
guilders, and experts and art lovers would come
from all over the world and pay money to see it.
Today, it is worth nothing, and nobody would
cross the street to see it for free. But the
picture has not changed. What has?"  Van
Meegeren, 1947 trial for forgery
FAKE
Art dealer Otto Wacker put 33 fake Van Goghs on
the market
Sold for 39.9 million dollars
???
FAKE
FAKE
Hung in a museum for 50 years
Metropolitan Museum paid 50 million dollars
FAKE
Forger was almost sentenced to life in prison
Pretend Picasso
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How Can a Forgery be Revealed?

• Artistic style
• Provenance
• Scientific Analysis

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Which is the real Jackson Pollock painting?
New York Times
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32 Paintings Were Found in This Wrapper

• Pollock (194649) Tudor City (19401949)
• 32 Jackson experimental works (gift purchase)
  Bad condition.
• 4 both sides. All
• drawing boards.
• Robi paints.
• MacDougal Alley, 1958.

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Paintings and Provenance
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Expert Opinion

• Ellen Landau
• Art scholar, Case Western University
• Expert on authentication of works by Pollock
• Thought Matter paintings were authentic

• Francis OConnor
• Compiled Catalogue Raisone of Pollocks works
• Said Matter paintings were fakes

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Forensic Analysis

• Jackson Pollock died in 1956
• Analysis of materials can inform
• Pigments have a known history

10
Pigments as Historic Artifacts

• Choice of colorants has changed for artists
  throughout history based on availability
• Cave paintings of Lascaux, France
• Minerals used

Photo M. Burkitt 'The Old Stone Age' (1955),
after Breuil

• Hematite or iron red oxide -Fe2O3
• Limonite or yellow ocher FeO(OH)nH2O
• Charcoal or carbon - C
• Manganese dioxide - MnO2
• http//www.donsmaps.com/cavepaintings.html

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More Colored Minerals

• Ancient Egyptians ground minerals
• Red lead (Pb3O4)
• Malachite (CuCO3)
• Orpiment (As2S3)
• Manufactured Egyptian Blue first synthetic
  pigment
• (CaCuS4O10)

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Preparation of More Pigments Devised

• Lead white - lead(II) carbonate
• PbCO3
• Verdigris copper(II) acetate
• Cu(CH3COO)2
• Ultramarine blue (1828)
• (Na8-10Al6Si6O24S2-4)

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Mauve First Artificial Organic Dye

• Synthesized in 1856 by the 18 year old William
  Perkins
• He was trying to make quinine from coal tar
• Mixed aniline, toluidine and methanol started
  an industry

http//ce.t.soka.ac.jp/chem/iwanami/intorduct/ch11
synthesis.pdf
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Color Index

• 12000 products with 1700 generic names
• All products are given a color index unique
  identifier
• 10 pigment codes PB, PBk, PBr, PG, PM, PO, PR,
  PV, PW, PY
• Constitution number sequential number given as
  new pigments are added to the index

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Colored Compounds

• Variety of structural characteristics will make a
  compound appear colored
• Fundamental similarity all capable of absorbing
  selected wavelengths of light
• When light is absorbed, electrons go to higher
  energy levels
• Energy of the transition determines wavelength
  that is subtracted
• Color we see are wavelengths not absorbed

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Color Perceptionhttp//www.chem.purdue.edu/gchelp
/cchem/color2.html

• Color absorbed
• Red -------------------------?
• Orange --------------------?
• Yellow ---------------------?
• Lemon Yellow -----------?
• Green ----------------------?
• Blue-green ----------------?
• Blue ------------------------?
• Indigo ----------------------?
• Violet -----------------------?

• Color seen
• Blue-green
• Blue
• Indigo
• Violet
• Purple
• Red
• Orange
• Yellow
• Lemon Yellow

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Color of Inorganic Pigments

• Ligand field effects (iron oxide reds and
  yellows)
• Charge transfer (chromates and ultramarines)
• Pure semi-conductors (cadmium yellows and
  oranges)

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Coordination Compounds

• Metal atom or ion surrounded by ligands
• Crystal field theory explains splitting of d
  orbitals due to influence of ligands
• Excitation of electrons from one d level to
  another

Chang, 2002
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Charge Transfer

• An electron moves from one atom to another in a
  compound
• In Prussian blue
• Fe(II) reduces Fe(III) and it is oxidized to
  Fe(III)
• Fe(III)4Fe(II)(CN)63xH2O

Simple cubic lattice of Prussian blue. Fe(II)
yellow Fe(III) red C gray N blue
Ware, 2008
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Semiconductor

• Vermillion (HgS) and Cadmium yellow (CdS)
• Forbidden energy level in between allowed levels
  - called a band gap
• If an electron is promoted to the conduction
  band, all the energies above the conduction band
  are absorbed

http//www.nanolytics.de/index.php?lgenmainfiel
d_of_businesssubwhy_colloids
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Absorbance - Charge Transfer Versus Semiconductor

• Charge transfer absorbs a narrow wavelength
• If green is absorbed, colors on either side will
  be reflected
• Red and blue will be seen, therefore the color
  seen is purple

• Semiconductors absorb a band of color
• If green is absorbed, all colors with higher
  frequency than green will be absorbed (green and
  blue)
• Yellow and red reflected, therefore orange will
  be seen

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Conjugated Double Bonds

• p electrons delocalized over length of the
  conjugation
• Particle on a line model can be used to calculate
  the transition energy from the ground state to
  the excited state

Methylene blue http//omlc.ogi.edu/spectra/mb/inde
x.html
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Pigments and Paints

• Technically- artists use paints
• Paints consist of 4 parts which may interfere
  with each other in an analysis
• Pigment(s)
• Medium or binder for suspension
• Diluent
• Additives

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Methods of Analysis Complement One Another

• Fourier Transform Infrared Spectroscopy (FTIR)
• Raman Spectroscopy
• Laser Desorption Time of Flight Mass Spectrometry
• Pyrolysis Gas Chromatography/ Mass Spectrometry
• Scanning Electron Microscope / Energy Dispersive
  X-Ray Analysis

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IR versus FTIR

• IR
• IR Spectroscopy uses the absorption of infrared
  light measured as a function of wavelength to
  identify molecular compounds
• Vibrations that make changes in dipole moment are
  observed
• Spectrum is like a fingerprint

• FTIR
• Two mirror system
• One stationary, one pulses in coordination with
  laser
• Light source is split into 2 beams which go to
  the 2 mirrors then are directed back to splitter
• When beams combine, it is an interferogram
• Interferogram is directed at the sample
• Some energy is absorbed, transmitted energy is
  read by detector
• Data from detector is modified using an algorithm
  known as a Fourier transform

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• Dispersive IR
• Monochromator
• Diffraction grating or prism
• Breaks light into individual frequencies
• Slow scanning speed

http//www.umaine.edu/misl/ft_spectrometer.html
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Raman Spectroscopy

• Raman effect refers to small amount of light that
  scatters inelastically from a molecule, at a
  different wavelength than the incident light
• This absorbed energy is an intrinsic property of
  the molecule, independent of the incident
  wavelength
• Raman instruments use lasers, wavelength chosen
  to give best signal to noise ratio.
• Advantage of Raman - New instruments allow one to
  do analysis without any destruction of the sample

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Mass Spectrometry

• Fragments molecules into ions using one of a
  number of techniques
• Fragments are separated on the basis of mass to
  charge ratio (m/z) by magnetic or electric field
• Molecular weight of the compound and mass of
  major ions gives information that helps elucidate
  the structure

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Mass Spec Systems Used for Art Analysis

• LDI-TOF-MS
• Laser desorption volatilizes and fragments the
  molecule
• No sample preparation only very small sample
  needed
• Time of flight refers to the detection system
  that relies on the time it takes to reach the
  detector correlating with the molecular weight

• Py-GC-MS
• Used for large molecules
• Generally used for polymer analysis
• Volatilizes sample by rapid heating on platinum
  wire, then sample is introduced into from a GC

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SEM/EDX

• Useful for analyzing a pigment with a limited
  number of elements
• High energy electromagnetic radiation directed at
  sample
• Beam dislodges electron from sample
• Higher energy electron from sample replaces
  missing electron and photon is released
• Energy of photon is measured to determine
  elemental source of emission

http//www.geosci.ipfw.edu/sem/semedx.html
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Harvard University Art Museums

• Three works thought to be by Jackson Pollock
  (1912-1956) and owned by Alex Matter were
  analyzed using a variety of techniques to
  determine age and composition of materials

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Raman and SEM/EDX
http//www.artmuseums.harvard.edu/home/HUAMreport0
12907.pdf
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LDI-TOF Mass Spectrometry
http//
www.artmuseums.harvard.edu/home/HUAMreport012907.p
df
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Fourier Transform IR
http//www.artmuseums.harvard.edu/home/HUAMreport0
12907.pdf
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PR254 Diketopyrrolo-Pyrrole (DPP) Pigment
Herbst, 2004
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PR254 Mass Spectrometry Spectrum
Sodiated and di-sodiated species
Loss of CO
Wyplosz
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Mass Spectrum of Paint from a Car Fender Panel
Shows presence of both Quinacridone Red ( MW 312)
and PR254 (MW 356)
Stachura, et al., 2007
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FTIR Spectrum of PR254 in Car Paint of Suspected
Vehicle and Damaged Bumper
Suspected hit and run vehicle
Damaged car bumper
Reference sample of PR254
Buzzini, et al., 2006
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Raman Spectra Comparing Paint from a Damaged
Bumper and a Suspected Vehicle
Damaged Car Bumper
?exc 785 nm
Suspected Hit and Run Vehicle
PR254 was identified, due to its Raman bands.
Buzzini, et al., 2006
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Pyrolysis GC Mass Spectrometry
http//www.artmuseums.harvard.edu/home/HUAMreport0
12907.pdf
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Conclusions

• Pigment analysis is useful for authentication of
  art works and new analytical techniques are
  improving the analyses
• Databases of spectra are needed for pigment data
  
• Even with objective scientific data, experts from
  the art world are not in agreement over the
  Matter paintings

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