Chemical Analysis of Artwork · 2020. 11. 10. · Importance • Examine the authenticity of...

Analytical Strategy 2020

Chemical Analysis of ArtworkAndras KovacsZhiyuan FanAshling FaehMichael Chanton

Importance

• Examine the authenticity of artifacts

• Obtain information about the materials and methods used by the artist

• Develop techniques and materials for restorations

• Determine the age and origin of artworks

10.11.2020Analytical Strategy 2020 2

Realtive dating

• A method of determining whether an object is younger or older than another object

• Relation to known events or documents

• Not specific or exact


Absolute dating

• Measuring the age of an object in years

• Analysis of physical and chemical properties

• A variety of methods

− Radiometric dating

− Dendrochronology

− Thermoluminescence dating


Thermoluminescence dating

• All objects absorb radiation from the enviroment

− Frees electrons in the material → can get trapped

• Upon heating, trapped electrons are released

− 1st heating: Zeroing event (making the artifact)

− 2nd heating: age determination (present)

• Measure the accumulated radiation dose

• Perfect method for ceramics


Mary-Anne Seeley: Journal of Acheological Science 2 1975 17-43

Analysis of paintings

• Analysis of ground layers, underdrawins and varnish

• Determination of the support material

− Type of wood used for the frame

− Fibre of the canvas

• Composition of the paint

− Pigment

− Binder

• Craquelure pattern

• Signature verification


Montani Isabelle, 2015, Exploring transparent approaches to the authentication of signatures on artwork

Analysis of ceramics

• Composition of the paint

− Pigment

− Binder

• Age of the material

− Thermoluminescence


http://ceramics.chalre.com/detecting_fake_ceramics/sample_fake_ceramics.htm

Analysis of marble statues

• Style and iconography

− Not so challenging to copy

• Identification of the querry

− Isotope ratios

− Trace elements

• Analysis of the surface

− Ages overtime → patina formation


Stanley V. Margolis Scientific American , Vol. 260, No. 6 (JUNE 1989), pp. 104-111

Analysis of wooden caskets


Relative Dating

• Some of the wooden caskets are painted

• Some pigments and binding media are only used in a short period of time in history

• Identifying these pigments and binding media provides relative dating

Analytical Strategy 2020 10.11.2020 10

https://sammlung.nationalmuseum.ch/de/list?sID=22

Common Pigments


http://www.webexhibits.org/pigments/intro/pigments.html

Artists' pigments : a handbook of their history and

characteristics, 1997, 3 volumes.

New York: Oxford University Press

History of Use of Common Pigments


http://www.webexhibits.org/pigments/intro/pigments.html

Azurite (2CuCO3·Cu(OH)2)

Carbon black

Chrome orange (PbCrO4·Pb(OH)2)

Cobalt green (CoO·ZnO)

Green earth (complex aluminosilicate with Fe)

Lead white (2PbCO3·Pb(OH)2)

Naples yellow (lead antimonate)

Smalt (cobalt aluminosilicate)

Vermilion (HgS)

Zinc white (ZnO)

Bone black (Ca3(PO4)2+CaCO3+C)

Chrome yellow (PbCrO4)

Lead-tin yellow (Pb2SnO4)

Madder lake (alizarin or purpurin)

Identification: Optical Microscopy


Artists' pigments : a handbook of their history and characteristics, 1997, 3 volumes.New York: Oxford University Press

Indian yellow, without andwith polarizers

Another type of Indianyellow

Cobalt yellow

Identification: Instrumental Methods


2θ

X-ray diffraction

Infrared

Cobalt yellow

Cobalt yellow


Criteria for Positive Identification



Example: Indian yellow

• a) yellow pigment that fluoresces yellow to orange under long wavelength ultraviolet light;

• b) particles of intense yellow color when examined microscopically under plane polarized light;

• c) highly birefringent particles of a refractive index about 1.67, yellow in transmitted light and yellow-to-green under crossed polars, showing olive hues in the thicker particles, usually rather coarse in particle size and irregular-to-prismatic in shape exhibiting parallel extinction and positive elongation (samples from Indian paintings do not show such particles);

• d) all yellow particles should dissolve in dilute mineral acids;

• e) infrared curve similar to standard sample.

Truly Non-Destructive Methods


Non-destructive microanalysis of cultural heritage materials. K. Janssensand R. Van Grieken (Eds). Amsterdam: Elsevier. 2004.

https://www.stellarnet.us/https://www.oceaninsight.com/

• Fiber-optic Raman spectroscopy

• Fiber-optic fluorescence spectroscopy

• Non-destructive infrared spectroscopy

Optical fiber for Raman and fluorescence spectroscopy

StellarCASE-NIR analyzer

Absolute Dating – non-destructive


Dendrochronology

• Width of tree rings indicates area of growth

• Determine felling year based on comparisons of tree ring patterns of different trees

• Chronological sequence by matching overlapping sequences up to live trees

• Connects different works of art from same area

• Softwood species easier to date than Hardwood


Olstad, T. M.; Stornes, J. M.; Bartholin, T. S. When Dendrochronology Corroborates: Art History. Eur. J. Sci. Theol.2015, 11 (2), 159–169https://www.thecanadianencyclopedia.ca/en/article/dating-in-archaeology, accessed 05.11.20Ferguson, C. W. Concepts and Techniques of Dendrochronology. Sci. Methods Mediev. Archaeol. 1970, 183–200

https://www.thecanadianencyclopedia.ca/en/article/dating-in-archaeology

Methods – Photography/ Microscopy

• Surface is depicted and curves of tree rings drawn

• Issues if surface is coated with substances e.g. paint, lacquer

• Issues if wood is degraded

• Often surface needs to be prepared by grinding or cutting parts off destructive


Okochi, T.; Hoshino, Y.; Fujii, H.; Mitsutani, T. Nondestructive Tree-Ring Measurements for Japanese Oak and Japanese Beech Using Micro-Focus X-Ray Computed Tomography. Dendrochronologia 2007, 24 (2–3), 155–164Bill, J.; Daly, A.; Johnsen, Ø.; Dalen, K. S. DendroCT - Dendrochronology without Damage. Dendrochronologia2012, 30 (3), 223–230

Methods - X-ray computed tomography

• Images interior part of wood

• Medical grade X-ray CT can not resolve less than 1mm

micro-focused X-ray CT


Okochi, T.; Hoshino, Y.; Fujii, H.; Mitsutani, T. Nondestructive Tree-Ring Measurements for Japanese Oak and Japanese Beech Using Micro-Focus X-Ray Computed Tomography. Dendrochronologia 2007, 24 (2–3), 155–164https://www.ssi.shimadzu.com/products/non-destructive-x-ray-testing/inspexio-smx-100ct-software.html, accessed05.11.20

https://www.ssi.shimadzu.com/products/non-destructive-x-ray-testing/inspexio-smx-100ct-software.html

Methods - X-ray computed tomography

• X-rays generated in X-ray source

• Decrease in intensity as X-rays pass through sample

• Characterized by Lambert-Beer’s law: I = I0 e-μd

• Rotate sample and take another image

• Computer constructs cross section slices


Okochi, T.; Hoshino, Y.; Fujii, H.; Mitsutani, T. Nondestructive Tree-Ring Measurements for Japanese Oak and Japanese Beech Using Micro-Focus X-Ray Computed Tomography. Dendrochronologia 2007, 24 (2–3), 155–164Bill, J.; Daly, A.; Johnsen, Ø.; Dalen, K. S. DendroCT - Dendrochronology without Damage. Dendrochronologia2012, 30 (3), 223–230https://www.microphotonics.com/what-is-micro-ct-an-introduction/, accessed 05.11.20

https://www.microphotonics.com/what-is-micro-ct-an-introduction/https://www.microphotonics.com/what-is-micro-ct-an-introduction/

Methods - Neutron imaging

• Same attenuation principle as X-ray

• Different sensitivities as neutrons interact with nuclei and X-rays with electron shells

• Shorter exposure time than X-ray CT for wood samples


Mannes, D.; Lehmann, E.; Cherubini, P.; Niemz, P. Neutron Imaging versus Standard X-Ray Densitometry as Method to Measure Tree-Ring Wood Density. Trees - Struct. Funct. 2007, 21 (6), 605–612

Comparison

Benefits LimitationsPhotography/Microscopy

• Cheap• Simple• (Non-destructive)

• Wood rings need to be clearly visible

• Surfaces coated with substance are difficult

Micro X-ray CT • Very good resolution• Interior of wood can be

imaged• Non-destructive• No sample preparation

• Expensive• Few facilities available

Neutron imaging • Very good resolution• Non-destructive• No sample preparation• Short exposure time

• Very expensive• Few facilities available


Absolute Dating: Microinvasive

• Materials:− Metals (Lock, Key, Gold ornament)− Paint (Pb ratio, 14C)− Stones (Gemstones as ornament)− Wood (14C dating)


14C Method


Hajdas I. 2008. The Radiocarbon dating method and its applications in Quaternary studies. Quaternary Science Journal - Eiszeitalter und Gegenwart 57: p.3

12C 13C 14C

99.89% 0.1% 1 ppt

Stable Stable

12C/14C Ratio changes after death

Half-life of 14C is 5730 years

50'000-55'000 year old material can be dated

Radioactive decay calculable:

Sample Preparation

• 3-100 milligrams (AMS) of wood needed

• Ultrasonic - Pretreatment to remove dust

• Soxhlet (remove conservation compounds from museum)

• Prevent contamination, Freezing or drying (bacteria)

• Acid-Alkali-Acid method (AAA)

• [Acid-Base-Oxidation (ABOX) materials older

than 2000 Years]

• Final combustion 850°C


Hajdas I. 2008. The Radiocarbon dating method and its applications in Quaternary studies. Quaternary Science Journal - Eiszeitalter und Gegenwart 57: p.12

MICADAS type of an Accelerator Mass Spectrometry (AMS) technique


https://doi.org/10.1016/j.ijms.2013.05.008

• Negative Ion: 14C 14N separation

• Stripping process: − Separation of molecules and

radionuclides with same mass:

− Ultrathin foil or windowless gas cell− Coulomb forces: molecule

decomposes (3+)

VorführenderPräsentationsnotizenCs sputter ion source --> generares negative ions

https://doi.org/10.1016/j.ijms.2013.05.008

Age Determination


DOI: 10.1039/c9an02346a

• Measure activity of 14C or measure ratio of 14C/12C (AMS)

• Problem A0 not stable (Suess effect, Sun eruptions)

• Fractionation possible chemical and physical reactions (Photosynthesis)

14C coupled with Pb Isotope Ratio: Lead White Paint


DOI: 10.1039/c9an02346ahttps://www.researchgate.net/figure/Decay-series-of-A-uranium-238-238-U-B-uranium-235-235-U-and-C-thorium-232_fig4_313744940(07.Nov.2020)

• Ratio changes over time:− 208/207/206Pb− 204Pb is not a decay product

• Lead White:− Both measurement with same sample− (2PbCO3·Pb(OH)2)− 10–50 µg C needed− 3 to 30 mg lead white bearing paint was

collected, which resulted in 20–100 µg C

• ICP-MS/MICADAS

• Applicable for chests?

https://www.researchgate.net/figure/Decay-series-of-A-uranium-238-238-U-B-uranium-235-235-U-and-C-thorium-232_fig4_313744940

Further Ideas


https://www.photobash.org/medieval-keys (07.Nov.2020)

• Analysis of metal parts:

• Key could fit in ablation cell− Medieval keys are rare

• No information found on this− Metal composition

https://www.photobash.org/medieval-keys

Comparison

Method Benefits Limitations14C MICADAS (Wood, Paint) • Absolute dating method

• Wood is simple to sample and main compound

• Conservation of integrity

• Misinterpretations of new wood (CO2 pollution = Suess effect)

• Old wood effect (re-used materials)

ICP-MS (Pb Isotope Ratio in Paint)

• Few sample needed • Reference needed• Complicated data evaluation

(Interferences, Mixed paint, inhomogenieties)

• Lead white paint needed• Integrity ??


A large variety of effects must be considered in data evaluation. Further restoration history, representative sampling and combination of all presented techniques is important for this type of analysis.Determined age is the age of the wood not of the chest!!!

Questions?


Attachment: Soxhlet Set Up


https://www.researchgate.net/figure/Soxhlet-extraction-apparatus-set-up-33_fig2_326734330(07.Nov.2020)

https://www.researchgate.net/figure/Soxhlet-extraction-apparatus-set-up-33_fig2_326734330

Chemical Analysis of ArtworkImportanceRealtive datingAbsolute datingThermoluminescence datingAnalysis of paintingsAnalysis of ceramicsAnalysis of marble statuesAnalysis of wooden casketsRelative DatingCommon PigmentsHistory of Use of Common PigmentsIdentification: Optical MicroscopyIdentification: Instrumental MethodsCriteria for Positive IdentificationTruly Non-Destructive MethodsAbsolute Dating – non-destructiveDendrochronologyMethods – Photography/ MicroscopyMethods - X-ray computed tomographyMethods - X-ray computed tomographyMethods - Neutron imagingComparisonAbsolute Dating: Microinvasive 14C MethodSample PreparationMICADAS type of an Accelerator Mass Spectrometry (AMS) techniqueAge Determination14C coupled with Pb Isotope Ratio: Lead White PaintFurther Ideas ComparisonQuestions?Attachment: Soxhlet Set Up

Chemical Analysis of Artwork · 2020. 11. 10. · Importance • Examine the authenticity of...

Documents

Transcript of Chemical Analysis of Artwork · 2020. 11. 10. · Importance • Examine the authenticity of...