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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 l.jpg
Uncovering Art Forgery Using Analytical Chemistry

Patricia Munter

University of Pennsylvania

MCEP 2008

Art and science meet l.jpg
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 l.jpg


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


Art dealer Otto Wacker put 33 fake Van Goghs on the market

Sold for 39.9 million dollars




Hung in a museum for 50 years

Metropolitan Museum paid 50 million dollars


Forger was almost sentenced to life in prison

Pretend Picasso

How can a forgery be revealed l.jpg
How Can a Forgery be Revealed?

  • Artistic style

  • Provenance

  • Scientific Analysis

32 paintings were found in this wrapper l.jpg

“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

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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

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Forensic Analysis

  • Jackson Pollock died in 1956

  • Analysis of materials can inform

  • Pigments have a known history

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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 l.jpg
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 l.jpg
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


Color index l.jpg
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 l.jpg
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 l.jpg

Color absorbed

Red -------------------------

Orange --------------------

Yellow ---------------------

Lemon Yellow -----------

Green ----------------------

Blue-green ----------------

Blue ------------------------

Indigo ----------------------

Violet -----------------------

Color seen









Lemon Yellow

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

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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)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 l.jpg

  • 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


Absorbance charge transfer versus semiconductor l.jpg

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 l.jpg

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 l.jpg
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

Ir versus ftir l.jpg


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


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

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  • Dispersive IR

  • Monochromator

    • Diffraction grating or prism

    • Breaks light into individual frequencies

    • Slow scanning speed


Raman spectroscopy l.jpg
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 l.jpg
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 l.jpg


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


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 l.jpg

  • 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


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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

Raman and sem edx l.jpg
Raman and SEM/EDX


Ldi tof mass spectrometry l.jpg
LDI-TOF Mass Spectrometry



Fourier transform ir l.jpg
Fourier Transform IR


Pr254 mass spectrometry spectrum l.jpg
PR254 Mass Spectrometry Spectrum

Sodiated and di-sodiated species

Loss of CO


Mass spectrum of paint from a car fender panel l.jpg
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 l.jpg
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 l.jpg
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 l.jpg
Pyrolysis GC Mass Spectrometry Suspected Vehicle


Conclusions l.jpg
Conclusions Suspected Vehicle

  • 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 l.jpg

  • References Suspected Vehicle

  • Adar, F. Raman Applications That Are Driving a Rapidly Expanding Market. Spectroscopy. 2008, 23, 24-29.

  • Brill, T.B., Why Objects Appear as They Do. J. Chem. Educ. 1980, 57, 259-263.

  • 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

  • Hao, Z., Iqbal, A. Some Aspects of Organic Pigments, Chem. Soc. Rev. 1997, 26, 203-213

  • Herbst, W.; Industrial Organic Pigments; Wiley-VCH:Weinheim, Germany, 2004.

  • Jones-Smith, K., Mathur, H., Revisitng Pollock’s Drip Paintings, Nature2006, 444, E9-E10.

  • Kennedy, R., Drip Wars: A Pollock, in the Eyes of Art and Science. The New York Times. http://www.nytimes.com/2007/02/04/weekinreview/04kennedy.html?_r=2&ei=5088&en=e789e7a&oref (accessed 7/9/08).

  • Kincade, K. Laser-based Instrumentation Sheds New Light on Old Art. Laser FocusWorld. 2008, 44, 85-89.

  • Orna, M.V. Chemistry and Artist’s Colors: Part I. Light and Color. J. Chem. Educ. 1980, 57, 256-258.

  • Orna, M.V. Chemistry and Artist’s Colors: Part III. Preparation and Properties of Artist’s Pigments. J. Chem. Educ. 1980, 57, 267-269.

  • Orna, M.V. Chemistry, Color, and Art. J. Chem. Educ.2001, 78, 1305-1311.Papson, K., Stachura, S., Boralsky, L., Allison, J. Identification of Colorants in Pigmented Pen Inks by Laser Desorption Mass Spectrometry. J. Forensic Sci. 2008, 53, 100-106.

  • Papson, K., Stachura, S., Boralsky, L., Allison, J. Identification of Colorants in Pigmented Pen Inks by Laser Desorption Mass Spectrometry. J. Forensic Sci.2008, 53, 100-106.

  • Schulte, F., Brzezinka, K., Lutzenberger, K., Stege, H., Panne, U. Raman Spectroscopy of Synthetic Organic Pigments Used in 20th Century Works of Art. J. Raman. Spectrosc. [Online] 2008, Published online in Wiley Interscience. (www.interscience.wiley.com).

  • Stachura, S., Desiderio, V.J., Allison, J. Identification of Organic Pigments in Automotive Coatings Using Laser Desorption Mass Spectrometry. J. Forensic Sci. 2007, 52, 595-603.

  • Technical Analysis of Three Paintings Attributed to Jackson Pollock. http://www.artmuseums.harvard.edu/home/HUAMreport012907.pdf (accessed 7/9/08).

  • Ware, M., Prussian Blue: Artist’s Pigments and Chemists’ Sponge. J. Chem. Educ.2008, 85, 612-620.

  • Wyplosz, N., A Laser Desorption Mass Spectrometric Investigation of Artist’s Organic Pigments. PhD Dissertation (in preparation). University of Amsterdam, Amsterdam. [Online] http://www.amolf.nl/publications/theses/wyplosz/chapter_7.pdf (accessed 7/6/08).

  • Zollinger, H.; Color Chemistry: Synthesis, Properties and Applications of Organic Dyes and Pigments, 2nd revised edition; VCH: New York, 1991.