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SYNCHROTRON RADIATION SYNCHROTRON RADIATION SYNCHROTRON RADIATION AND ARCHAEOMETRYAND ARCHAEOMETRYAND ARCHAEOMETRY
Simona Quartieri Dipartimento di Scienze della Terra
Università di Messina
In general, the studies of ancient objects of archaeological or artistic interest have undergone significant improvements in the recent years under
the impulse of new non- or micro-destructive methods for analyzing materials, such as:
� micro-beam techniques� portable instruments� synchrotron radiation
There are many reasons for usingsynchrotron radiation in archaeometry:
i) X-ray beams with high intensity and low divergence, as produced at synchrotron radiation facilities, are highly suitable tools for examining fragile, valuableand/or unique artefacts with minimal or no damage.
ii) We can achieve information about major- and trace-level composition of the objects, about the chemicalstate of one or more atomic species and/or aboutcrystallographic phases, that are present in the materials even in very small concentrations.
iii) Since the materials and objects encountered in the field of art-analysis, archaeology and conservation are often complex in shape, covered with alterationlayers and/or may be highly heterogeneous, the use of X-ray micromicro beamsbeams is often mandatory to allow forthe measurement of local rather than bulk properties.
The questions that archaeologists ask more often regarding an object are:
� what material is it made of (composition)
� when was it made (dating)
� where was it made (provenance)
� how was it made (art technology)
� how can we avoid its destruction (conservation)
InformationInformation fromfrom SRSR--techniquestechniques��Elemental microanalysis down to the subElemental microanalysis down to the sub--ppmppm level is level is possible by means ofpossible by means of ��--XRF XRF (X(X--ray fluorescence analysis). ray fluorescence analysis).
��Local structural and chemical state determinations of Local structural and chemical state determinations of selected (trace) constituents are possible by applyingselected (trace) constituents are possible by applying XAFS XAFS and and ��--XAFSXAFS (X(X--ray absorption spectroscopy) ray absorption spectroscopy)
��Information on the presence and nature of crystalline Information on the presence and nature of crystalline phases can be obtained viaphases can be obtained via XRDXRD (X(X--ray diffraction), ray diffraction), which which usually employ Xusually employ X--ray photons with energies in the 0.5 to 30 ray photons with energies in the 0.5 to 30 keVkeV range. range.
��Entire objects may be bathed in highlyEntire objects may be bathed in highly--energetic energetic synchrotron beams to allow high qualitysynchrotron beams to allow high quality radiographicradiographic orortomographictomographic imagingimaging measurements, revealing the internal measurements, revealing the internal structure of these structure of these artefactsartefacts..
Powder diffraction is a very widely applied technique in the geological and material sciences, even with conventional sources. When it is supported by the use of SR, it can provide excellent signal/noise ratios and strong peak resolution. Moreover, SR allows performing micro-diffractometric investigations.
The analysis of cosmetic samples is delicate since they are often heterogeneous at micron scale and may be composed of a mixture of organic and inorganic phases.
Their study requires non-destructive techniques, with high detectivity, high lateral resolution, and high chemical sensitivity (atomic, molecular and structural probes).
Manufacturing cosmetics in ancient EgyptManufacturing cosmetics in ancient EgyptStudy of cosmetic powders from ancient Egypt, dating from 2000 to 1200 BC, that were preserved in their original containers
Manufacturing Manufacturing cosmeticscosmetics in in ancientancient EgyptEgypt
Manufacturing Manufacturing cosmeticscosmetics in in ancientancient EgyptEgypt
Laurionite and phosgenite are very rare in nature and could not have been extracted from the mines in sufficient quantities for the preparation of the cosmetics
Intentionally manufactured by artificial synthesis !
Laurionite (PbOHCl) and phosgenite (Pb2CO3Cl2) could in principle had been formed for alteration of the basic components by chloride, but no foreign cationsor chlorinated phases were detected in the more than 50 analyzed samples. Therefore the alteration of natural lead minerals within the make-up is unlikely.
The synthetic or natural origin of a product can be distinguished by the analysis of the
diffraction peak profiles
The synthetic origin of PbOHCl e Pb2Cl2CO3 has been confirmed by the analysis of the diffraction peak profiles, comparing the effects due to the strains and to the crystallite dimensions with those present in the natural phases.
RESULTS:1- galena present in the cosmetics was crashed, probably to confer the make-up the desired texture and brightness2- the peak profiles of laurionite and phosgenitedo not exhibit strain effects, suggesting that the crystallites were produced by direct synthesis.
XRD LINE PROFILE ANALYSISXRD LINE PROFILE ANALYSIS
Why to produce white components to be added togalena when cerrusite was available?
In the ancient Egypt, cosmetics were not only used for aesthetic purposes, but also for their therapeutic, hygienic and magic properties. The Greco-Roman texts mention that the white precipitates synthesized by PbO were good for eye and skin care. These lead compounds could be used as bactericides and as a protection for the eye against exposure to the sun’s rays.
Marine Cotte, ID21, ESRF
The advantages of classical IR spectroscopy (non destructive, simultaneous information on both organic and mineral phases and on both composition and structure) are enhanced by the use of SR brightness (high lateral resolution with high signal-to-noise ratio).
20062006
The organic phase is composed of lead soaps, among which lead palmitate, and is located in the core of the particles.
In contrast, phosgenite (Pb2CO3Cl2) is detected mainly near the surface, which suggests that it was added at the end of the preparation, probably to keep it intact and more accessible for a possible therapeutic action.
Conclusions
MAYA BLUEMAYA BLUE PIGMENTPIGMENT
G.G. Chiari, R. Chiari, R. GiustettoGiustetto, G. , G. RicchiardiRicchiardi (2003) (2003)
EurEur. J. . J. MineralMineral.. 15:2115:21--3333
G.G. Chiari (2005) Chiari (2005) IUCrIUCr, Firenze, Firenze
In Mexico it was used until the end of ‘600. In Cuba it is found on walls dating 1830. It was “re-discovered” in 1849, together with the remains of the Maya civilisation.
Maya BlueMaya Blue is a synthetic pigment, produced by the Mayas probably around the VIII century AD
A bright turquoise, it was used in mural paintings, statues, ceramics, codices, and even to tint prisoners to be sacrificed.
Maya BlueMaya Blue is extremely stable: it can resist the attack of boiling, concentrated nitric acid, alkali and any sort of organic solvents.
Its composition and structure was a mystery for a long time. Kleber (1967) proposed a mixture of the colourless clay palygorskite and the blue organic dye indigo:
he was righthe was right
PALYGORSKITE PALYGORSKITE [(Mg, Al)4 (Si)8 (O, OH, H2O)24 nH2O]
Micro-channels filled with weakly bound zeolitic H2OThe cations complete their coordination with tightly bound structural H2O
Fibrous clay (from few to some tens of �)
Indigo is one of the most common organic dye, known even in the ancient Egypt, India and China and largely used also by Romans. The Majasextracted it from the leaves of Indigoferasuffruticosa, a native plant of Mexico.
Several hypotheses were proposed on how Maya Blue was produced using only the crude technology at the Mayas disposal
Palygorskite projected on (001)
Following one of these hypothesis, upon heating around 100° C, indigo would enter the palygorskite channels expelling the weakly bonded water molecules and forming strong chemical bonding interactions with the clay structure, so giving rise to the pigment Maya Blue.
Maja Blue pigment ?
SR X-ray powder diffraction at GILDA beamline
The powder patterns of paligorskite and of the clay-dye complex were very similar, due to the very low amount of dye which interact with the clay mineral, hence SR-XRPD was applied to obtain a better peak-to-background ratio and a better angular resolution.
Electron Density map at the level of indigo
Indigo
MODEL OF ENCAPSULATION OF INDIGO IN THE PALYGORSKITE FRAMEWORK
This configuration is extremely unlikely from the energetic point of view and, moreover, it is invalidated by two simple considerations:
Indigo can enter palygorskite channels only if the zeolitic water is removed (130 < T < 220°C).
HoweverHowever,, MAYA BLUEMAYA BLUE forms at about T=100°C !!
Even if indigo could displace water, the molecule has to break strong H bonds (� 1.8 Å between
indigo -C=O and structural water) to move inside the channels.
The formation of The formation of MAYA BLUEMAYA BLUE depends upon a depends upon a series of highly unlikely eventsseries of highly unlikely events.
ThermalThermal AnalysisAnalysis of of paligorskitepaligorskite (black) (black) and Maya Blue (and Maya Blue (redred))
The water loss at 120<T<300°C (ZEOLITIC ZEOLITIC water) is the sameis the same for both palygorskite and Maya Blue:
the two substances contain the same amount of water
A new theory is needed:A new theory is needed:
Indigo does not enter the channels but only Indigo does not enter the channels but only fills the grooves all around the crystalfills the grooves all around the crystal
Water
Indigo
H2O
Indigo
Indigo molecules are imbedded into the grooves.
Water does not have access to the groove because the hydrophobic part of indigo repels it.
Nitric acid cannot attack the indigo double bond because of steric hindrance.
Archaeometric applications of X-ray Absorption Spectroscopy
XAFS spectroscopy is a potentially very usefultechnique to be applied in archaeological studies.
�It is a non-destructive method which can be applied in air
�it virtually does not require any restriction on the type and size of the sample (metal, ceramic, glass, cloth, paper, etc.)
�it is applicable to most of the elements of interest, even in very low concentration.
All these characteristics are particularly important in archaeological applications, in which samples are precious cultural heritage made of very differentmaterials.
The The originorigin of color of color in in ancientancient glassglass
Various colors in glass can be causedby metal ions in them.
They are usually transition elementswhich absorb characteristicfrequencies of visible region.
This mechanism is also influenced bythe oxidation state of the metal cation.
Since the characterization of colorant and decolorant componentsis important in understanding the
manufacturing technique, XAFS has been applied to the study of the oxidation state of transition metals
in a number of glass samplescharacterized by different color
Application of X-ray Absorption Spectroscopy with synchrotron radiation to the study of glasses of archaeological interest
(Quartieri et al. Eur. J. Mineral. 2002)
Synchrotron X-ray absorption spectroscopy has been applied to the study of the oxidation state of iron and manganese in a number of glass samples of the 2nd century AD, characterized by different color (from pale green to pale brown) found in the Roman villa of Patti, near Messina.
AIMS
-to test the influence of iron oxidationstate on the color of the studied samples
- to identify the possible decolorant roleof manganese oxide in the almostuncolored samples
Fe and Mn K-edge absorption spectroscopy experiments were focused to XANES and pre-edge regions, being these particularly sensitive to both coordination and oxidation state of the absorbing atom.
The spectra were collected directly on the glass fragments in the fluorescence mode on the GILDA-CRG beamline (ESRF).
SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O NiO Cu2O CoO Cr2O3 ClA 70.70 0.10 3.31 0.40 0.02 0.63 8.02 16.45 0.59 0.02 0.06 0.02 — 0.99B 65.89 0.18 3.39 1.00 1.20 1.11 8.98 14.31 1.15 0.06 0.03 — 0.02 0.91
C 65.51 0.20 2.83 0.97 1.40 1.24 8.72 17.45 0.69 — 0.06 0.02 0.01 0.88
ExperimentalChemical analyses of the glass samples.
Glass A: green; glass B: uncolored; glass C: pale brown.A
Fe K-edge
7100 7125 7150 7175
Nor
m. A
bsor
ptio
n
Energy (eV)
C
Olivine
Hematite
Magnetite
B
A
abcd
Glass A
7112.4 7113.9
7114.6
7110 7112 7114 7116 7118Energy (eV)
0
0.1
0.2
0.3
0.4
Nor
m. A
bsor
banc
e
Glass B
7112.3
7114
7110 7112 7114 7116 7118Energy (eV)
-0.5
0
0.5
1
1.5
2
Nor
m. A
bsor
banc
e
Glass C
7112.3
7114
7110 7112 7114 7116 7118Energy (eV)
0
0.2
0.4
0.6
0.8
1
Nor
m. A
bsor
banc
e
Olivine
7112.4
7113.6
7114.4
7110 7112 7114 7116 7118Energy (eV)
0
0.01
0.02
Nor
m. A
bsor
banc
e
Magnetite
7112.3
7114
7115.4
7110 7112 7114 7116 7118Energy (eV)
0
0.02
0.04
0.06
0.08
Nor
m. A
bsor
ptio
n
Hematite
7113.2
7114.5
7115.7
7110 7112 7114 7116 7118Energy (eV)
-0.005
0.005
0.015
0.025
0.035
Nor
m. A
bsor
ptio
n
Roman glass samples
Reference compounds
Fe K-edge:
6530 6540 6550 6560 6570
Nor
m. A
bsor
ptio
n
Energy (eV)
MnO
Glass B
Glass C
MnO2
Mn2O
3ab
c d
6540 6550 6560
Nor
m. A
bsor
ptio
n
Energy (eV)
Glass B
Glass C
Rhodonite
Tephroite
Mn K-edge
In glass B and C Mn is in the reduced form
In the ancient glass B and C Mn4+ has oxidized Fe2+ to Fe3+ and, as a consequence, is present in the reduced form.
This confirms the hypothesis of a redoxinteraction between iron and manganese, as a result of a deliberate addition of pyrolusite �reported in literature as one of the main decolorants in the Roman period � during the melting procedure of the almost uncoloredglasses.
Results
Polycrome Etruscan glass: archaeometric data from synchrotron
�XRF, �XANES and XRPDArletti R., Vezzalini G., Quartieri S., Malnati L., Ferrari D., D’Acapito F., Merlini M., Cotte M.
APA 2008
The work was aimed to the characterization of coloring and opacifying agents in a series of very rare, highly decorated and coloured glass vessels and beads from VII to IV century B.C, found in Etruscan contexts.
All the finds were entire and very well preserved, so a totally not destructive approach was mandatory:
μ-XRF, μ-XANES, XRPD
Quartieri - Duino 2009
AnalysedAnalysed samples: vesselssamples: vessels
Amphoriskos500 B.C.(Bologna)
8.5
cm
2.8 cm Ø
6.5
cm
3 cm Ø min5.1 cm Ø max
AryballosHalf V cen. B.C.
(Spina)Alabastron
Half V cen. B.C.(Modena)
9.2
cm
2.9 cm Ø
Mediterranean UnguentariaProduction sites not ascertained, probably imported from Greece (Rodi)
Quartieri - Duino 2009
ExperimentalExperimental
��XRF�-XANES (Fe and Mn K-edge)
@ ID21 (ESRF- Grenoble)
Quartieri - Duino 2009
ExperimentalExperimental@ BM08 (ESRF- Grenoble)��XRD
Quartieri - Duino 2009
AryballosAryballos (V (V cencen B.CB.C.).)Pb Sb
�-XRF
Quartieri - Duino 2009
����XRFXRF
��XRF point analyses on each stripe
Dark Navy #8
8
Turquoise #7
7
Yellow #6
6 Turquoise #5
5
Dark Navy #4
4
Navy #3
3
Quartieri - Duino 2009
����XRFXRF
1000 2000 3000 4000 5000 6000 7000 8000
turquoise6_yellow3_navy4_dark navy
0
1000
2000
3000
4000
5000
6000
7000
8000
Energy eV
Pb
3200 3400 3600 3800 4000 4200 4400
7_turquoise6_yellow3_navy8_dark navy
Energy (eV)
Sb
High Sb levels in the turquoise decorations, lower in the yellow ones
High Pb levels in the yellow decorations
No Pb and Sb evidences in the dark navy portions BULK GLASS
Sb
Quartieri - Duino 2009
SRSR--XRPDXRPD
200
400
600
800
1000
1200
1400
1600
8 12 16 20 24 28 32
Aryballos XRD
Yellow decorationturquoise decoration
Inte
nsity
(cou
nts)
2 theta
• Ca2Sb2O7 + CaSb2O6
• Pb2Sb2O7
DARK NAVY:large band typical of amorphous materials
BULK GLASSon which decorations
were realized
Quartieri - Duino 2009
7100 7150 7200
YellowTurquoiseDark navy
Nor
m. A
bsor
ptio
n (a
.u)
Energy (eV)
7114.1
7112.6
7114.8
7110 7112 7114 71160
0.005
0.01
0.015
0.02
0.025
Dark navy glass
7114.3
7113.3 7114.8
7110 7112.3 7114.7 71170
0.005
0.01
0.015
0.02
0.025
7114.1
7113.17115
7110 7112 7114 7116
0.005
0.015
0.025
0.035
Turquoise decoration Yellow decoration
XANES spectra show different Fe speciation between glass and decorations
DominantFe2+in bulk glass
DominantFe3+ in decorations
��--XANES mapping: Fe KXANES mapping: Fe K--edgeedge
Quartieri - Duino 2009
ConclusionsConclusions• First data on colouring and opacifyng agents of Iron age handcrafts.
Ca2Sb2O7-CaSb2O6Pb2Sb2O7
Continuity with the Roman Age
• Differences in Fe speciation:
a) Fe3+ in the decorations b) Fe2+ in bulk glass
two different manufacturing procedure steps