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Uncovering Art Forgery Using Analytical Chemistry Patricia Munter University of Pennsylvania MCEP 2008 Art and Science Meet Many museums house laboratories for materials analysis Mainly for restoration and conservation Sometimes materials analysis can authenticate a work

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uncovering art forgery using analytical chemistry
Uncovering Art Forgery Using Analytical Chemistry

Patricia Munter

University of Pennsylvania

MCEP 2008

art and science meet
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?
real or fake

FAKE

Real or 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

how can a forgery be revealed
How Can a Forgery be Revealed?
  • Artistic style
  • Provenance
  • Scientific Analysis
32 paintings were found in this wrapper
“Pollock (1946–49) Tudor City (1940–1949)

32 Jackson experimental works (gift & purchase) Bad condition.

4 both sides. All

drawing boards.

Robi paints.

MacDougal Alley, 1958.”

32 Paintings Were Found in This Wrapper
expert opinion
Ellen Landau

Art scholar, Case Western University

Expert on authentication of works by Pollock

Thought Matter paintings were authentic

Francis O’Connor

Compiled Catalogue Raisone of Pollock’s works

Said Matter paintings were fakes

Expert Opinion
forensic analysis
Forensic Analysis
  • Jackson Pollock died in 1956
  • Analysis of materials can inform
  • Pigments have a known history
pigments as historic artifacts
Pigments as Historic Artifacts
  • Choice of colorants has changed for artists throughout history based on availability
  • Cave paintings of Lascaux, France
  • Minerals used
  • 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

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

more colored minerals
More Colored Minerals
  • Ancient Egyptians ground minerals
    • Red lead (Pb3O4)
    • Malachite (CuCO3)
    • Orpiment (As2S3)
  • Manufactured “Egyptian Blue” first synthetic pigment
    • (CaCuS4O10)
preparation of more pigments devised
Preparation of More Pigments Devised
  • Lead white - lead(II) carbonate
    • PbCO3
  • Verdigris – copper(II) acetate
    • Cu(CH3COO)2
  • Ultramarine blue (1828)
    • (Na8-10Al6Si6O24S2-4)
mauve first artificial organic dye
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/ch11synthesis.pdf

color index
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
colored compounds
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
color perception http 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

Color Perceptionhttp://www.chem.purdue.edu/gchelp/cchem/color2.html
color of inorganic pigments
Color of Inorganic Pigments
  • Ligand field effects (iron oxide reds and yellows)
  • Charge transfer (chromates and ultramarines)
  • Pure semi-conductors (cadmium yellows and oranges)
coordination compounds
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

charge transfer
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)4[Fe(II)(CN)6]3·xH2O

Simple cubic lattice of Prussian blue.

Fe(II) yellow

Fe(III) red

C gray

N blue

Ware, 2008

semiconductor
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?lg=en&main=field_of_business&sub=why_colloids

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

Absorbance - Charge Transfer Versus Semiconductor
conjugated double bonds
π 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

Conjugated Double Bonds

Methylene bluehttp://omlc.ogi.edu/spectra/mb/index.html

pigments and paints
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
methods of analysis complement one another
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
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

IR versus FTIR
slide26

Dispersive IR

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

http://www.umaine.edu/misl/ft_spectrometer.html

raman spectroscopy
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
mass spectrometry
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
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

Mass Spec Systems Used for Art Analysis
sem edx
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

harvard university art museums
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
raman and sem edx
Raman and SEM/EDX

http://www.artmuseums.harvard.edu/home/HUAMreport012907.pdf

ldi tof mass spectrometry
LDI-TOF Mass Spectrometry

http://

www.artmuseums.harvard.edu/home/HUAMreport012907.pdf

fourier transform ir
Fourier Transform IR

http://www.artmuseums.harvard.edu/home/HUAMreport012907.pdf

pr254 mass spectrometry spectrum
PR254 Mass Spectrometry Spectrum

Sodiated and di-sodiated species

Loss of CO

Wyplosz

mass spectrum of paint from a car fender panel
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

ftir spectrum of pr254 in car paint of suspected vehicle and damaged bumper
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

raman spectra comparing paint from a damaged bumper and a suspected vehicle
Raman Spectra Comparing Paint from a Damaged Bumper and a Suspected Vehicle

Damaged Car Bumper

λexc = 785 nm

Suspected Hit and Run Vehicle

PR254 was identified, due to its Raman bands.

Buzzini, et al., 2006

pyrolysis gc mass spectrometry
Pyrolysis GC Mass Spectrometry

http://www.artmuseums.harvard.edu/home/HUAMreport012907.pdf

conclusions
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
slide42

References

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  • Buzzini, P., Massonnet, G., Sermier, F.M., The Micro Raman Analysis of Paint Evidence In Criminalistics: Case Studies. J. Raman. Spectrosc. 2006, 37, 922-931.
  • FT-IR vs. Dispersive Infrared: Theory of Infrared Spectroscopy Instrumentation. http://www.thermo.com/eThermo/CMA/PDFs/Product/productPDF_21615.pdf (accessed 7/5/08).
  • Gardner, C.W. Annual James L. Waters Symposium at Pittcon: Raman Spectroscopy. J. Chem. Educ. 2007, 84, 49.
  • Gettens, R.J.; Painting Materials: A Short Encyclopedia; Dover Publications Inc.: New York, 1966
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  • Kincade, K. Laser-based Instrumentation Sheds New Light on Old Art. Laser FocusWorld. 2008, 44, 85-89.
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