XRF analysis of pigments on marble, easel and mural paintings Andreas Karydas Institute of Nuclear and Particle Physics NCSR “ Demokritos ” Agia Paraskevi Athenss, Greece karydas@inp.demokritos.gr
Outline Polychromy on marble, wall-paintings , stone materials, easel painting General approach ✓ Detection of at least one fingerprint pigment element – Pigment identification is modest. XRF is performing elemental analysis! Single at millimeter scale XRF measurement ✓ Detection of two or more fingerprint pigment elements at the same spot – Pigment identification is strong (narrow list of candidates) Scanning micro-XRF or Macroscopic XRF analysis ✓ Local association of two or more fingerprint pigment elements – Pigment identification is strong (narrow list of candidates) Trace element detection may help to discriminate pigments of the same type or to address provenance issues
In-situ XRF analyses. Delos Archaeological site of Delos 1873 - Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Papposilène, Délos, Musée Actual state Initial state Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Strategy of the in-situ analyses Observation Recording Mapping Delos Archaeological Museum National Archaeological Museum in Athens XRF analyses Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Photographic Techniques ✓ Raking Light ✓ Macrophotography ✓ Infra-red photography ✓ Ultraviolet photography Philippe Collet Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Macro-photography Délos, Musée, Aphrodite , Andreas Karydas, ICTP, Tuesday, 4 th June 2019
UV Photography Délos, Musée, Aphrodite Andreas Karydas, ICTP, Tuesday, 4 th June 2019
UV Photography The boots of Artemis … Artémis Elaphébole, Délos, Musée
Video-microscope examination Brigitte Bourgeois, CNRS, Louvre Museum
Inherent difficulties for the XRF analyses ➢ to the structure of the statues’ draperies, which often obstructed the access of the beam on the interior parts of their folds, where colour was preserved in larger and more homogeneous areas Andreas Karydas, ICTP, Tuesday, 4 th June 2019
XRF portable instrumentation @Delos X-Ray source & Detector Spectrometer Head Power supply Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Probe with radioisotope source Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Inherent difficulties for the XRF analyses ➢ to the excessive abrasion of pictorial layers and therefore the insufficient quantity of pigment to be analysed. Complementarity of the Applied analytical techniques The accurate documentation of traces of polychromy on the status’ surfaces by video optical microscopy allowed for the detection of pigments even in areas where they were entirely invisible macroscopically. In thes cases, the combination of the two techniques (XRF and optical microscopy) applied in-situ proved to be highly efficacious. Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Delian Raw Pigments Celadonite Organic Ochre Orpiment Jarosite Sulfur Flower Egyptian Blue Ochre Organic Black Celadonite Ochre Ochre Orpiment Ochre Sulfur Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Orpiment (As 2 S 3 ) vs Realgar ( α -As 4 S 4 ) As: 64.6% As: 71.7 % S: 32.8% S: 26.7 % Ca: 2.3 % Fe: 1.6 % Fe: 0.30 % 15 k kV As As /channel As As 3 /channel 10 10 3 10 10 S As As DP DP 2 DP DP 1 As As ts/ch Fe Fe S Ca Ca DP DP ts/ch 2 Fe Fe 10 10 unts Ba Ba Fe Fe 2 10 10 coun unts coun 1 10 10 1 10 10 0 10 10 2 4 6 8 10 10 12 12 14 14 0 10 10 2 4 6 8 10 10 12 12 14 14 X-ray E Energy (k (keV) X-ray E Energy (k (keV) XRD peak’s: 3 rd order (111), 4 th order (020) XRD peak: 4 th order (120), 2 nd order (320, 141) Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Crystallized vs “Amorphous” orpiment 4 10 10 15 k kV 15 k kV As As As As /channel /channel 3 10 10 3 10 10 As As S S As As DP 2 DP ts/ch DP DP 1 ts/ch Ca Ca unts 2 2 10 10 Fe Fe 10 10 unts Ba Ba coun coun 1 10 10 1 10 10 0 10 10 0 10 10 2 4 6 8 10 10 12 12 14 14 2 4 6 8 10 10 12 12 14 14 X-ray E Energy (k (keV) X-ray E Energy (k (keV) As: 64.6% S: 32.8% As: 64.7 % Ca: 2.3 % S: 35.3 % Fe: 0.30 % Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Yellow Raw pigments: Jarosite vs Yellow ochre 15 k kV 3 Fe Fe 4 15 k kV 10 10 10 10 Fe Fe /channel /channel Ca Ca Fe Fe Fe Fe 3 10 10 ts/ch ts/ch 2 10 10 S Ca Ca unts K unts 2 10 10 coun coun 1 10 10 1 10 10 0 10 10 0 10 10 2 4 6 8 10 10 12 12 14 14 2 4 6 8 10 10 12 12 14 14 X-ray E Energy (k (keV) X-ray E Energy (k (keV) Fe 2 O 3 : 53.5 % SO 3 : 27.9 % K 2 O : 2.0 % CaO : 1.9 % KFe 3 (SO 4 ) 2 (OH) 6 + α FeO-OH+Ca-comp Ca-comp + geothite? Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Green Raw Pigment: Celadonite K(Mg,Fe)(Fe,Al)Si 4 O 10 (OH) 2 4 10 10 15 k kV + Ca-compound /channel Fe Fe 3 10 10 Ca Ca ts/ch K unts 2 10 10 Si Si coun 1 10 10 SiO 2 : 53.1 % Fe 2 O 3 : 16.9 % 0 10 10 2 4 6 8 10 10 12 12 14 14 K 2 O : 7.1 % X-ray E Energy (k (keV) CaO : 8.8 % Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Egyptian Blue raw pellets CuCaSi 4 O 10 + interstitial glass + residual glass Very interesting the presence of Pb and Sn. 40 k kV Leaded bronze as a source Cu Cu /channel of copper? Pb Pb 3 10 10 Pb Pb Using SEM with back ts/ch scattered electron imaging Fe Fe Sn Sn Pb Pb unts Ca Ca 2 10 10 Pb and Sn were found in coun RhK hK Sn Sn association with a second phase (apart the pure 1 10 10 Egyptian Blue phase) consisted of interstitial 4 8 12 12 16 16 20 20 24 24 28 28 X-ray E Energy (k (keV) glass. (Kakouli, 2002) The inclusion of leaded glass in the pellets is a unique feature that chronologically agrees with the first occurrence of Ptolemaic leaded glass and glazed faience Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Organic Pink Raw Pigment 15 k kV Ca Ca 3 10 10 /channel Fe Fe As+Pb RhL hL Cu Cu ts/ch Si Si 40 kV unts 2 Al Al 10 10 3 10 coun As+Pb Sr counts/channel Pb Sr Fe Ca Cu * Ni 1 10 10 2 10 0 2 4 6 8 10 10 12 12 14 14 Zn X-ray E Energy (k (keV) Pb Br+As 1 10 2 4 6 8 10 12 14 16 18 X-ray Energy (keV) Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Organic Pink Raw Colorant ✓ The presence of Al and Si, the absence of any other inorganic mineral pigment provide enough evidence’s in order to characterise it as an organic colorant. ✓ Trace elements (except Sr) exhibit large inhomogeneities Concentrations are expressed in μ g/g: Fe: 1140 ± 380 Cu: 220 ± 100 Zn: 109 ± 50 As: 555 ± 253 Br: 95 ± 60 Sr: 276 ± 26 Pb: 643 ± 114 Large variations between elements (etc, As/Pb: 0.5 – 1.6) ✓ The presence of Bromine which may support an hypothesis for the dye’s possible origin from shellfish -murex purple Andreas Karydas, ICTP, Tuesday, 4 th June 2019
XRF spectrum of the marble substrate Artemis A4126/Marble surface Ca 3 10 counts/channel Rh-K lines 2 10 Sr Fe 1 10 0 10 2 4 6 8 10 12 14 16 18 20 22 24 X-ray Energy (keV) Andreas Karydas, ICTP, Tuesday, 4 th June 2019
Polychromy on marbles: The “palette’s” Natural inorganic 1. Pure pigments Synthetic inorganic Organic based colorants 2. Mixture of pigments 3. Superimposition of different pictorial layers Andreas Karydas, ICTP, Tuesday, 4 th June 2019
The palette, 1 : “Pure” colours Red-Ochre A1298 Fe 3 Ca 10 counts/channel 2 10 Cu Pb Pb Sr 1 10 0 10 2 4 6 8 10 12 14 16 18 X-ray Energy (keV) Natural occurred pigments Andreas Karydas, ICTP, Tuesday, 4 th June 2019
The palette, 1 : “Pure” colours A3473-Aphrodite Head-Terracota Deep Yellow Fe 3 10 counts/channel Fe 2 10 Ca Zr Rb Sr Yellow Ochre Zn Ti Pb 1 10 0 10 2 4 6 8 10 12 14 16 18 X-ray Energy (keV) Délos, Musée, Natural occurred Stèle de Kerdon pigment
The palette, 1 : “Pure” colours Natural occurred pigments, Malachite/Green Earth Papposilene Ca 3 10 counts/channel Cu 2 10 Sr Fe Cu Pb Pb 1 10 Artemis - A4126 4 10 Ca 0 10 2 4 6 8 10 12 14 16 18 counts/channel X-ray Energy (keV) 3 10 Fe Sr Pb Pb Zr 2 10 Fe Zn Délos, Musée, Hermès, 1 10 A 4256 0 10 2 4 6 8 10 12 14 16 18 X-ray Energy (keV) Malachite is characterized by its angular particle form. The colour of the coarser particles show high relief and dark edges, while the finer particles are nearly colourless
The palette, 1 : “Pure” colours Artificial pigment Pb 3 Pb 10 counts/channel ( PbCO3)2·Pb(OH)2 Pb 2 Ca 10 Pb Pb 1 10 0 10 2 4 6 8 10 12 14 16 X-ray Energy (keV) Lead White Andreas Karydas, ICTP, Tuesday, 4 th June 2019
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