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Thai Red Glass

Thai Red Glass

Understanding the Color of 19th Century Glass from Bangkok’s Temple of the Emerald Buddha Using 20th Century Theory and 21st Century Synchrotron Tools

Bruce Ravel

July 01, 2013
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  1. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Using 21st century spectroscopic tools with 20th century theory to
    understand the color of 19th century glass from Bangkok’s Temple of
    the Emerald Buddha
    Bruce Ravel1, Larry Carr2, Christophe Hauzenberger3, Wantana Klysubun4
    1NIST & NSLS Beamline X23A2
    2BNL, Photon Sciences
    3Karl-Franzens-University Graz, Austria
    4Synchrotron Light Research Institute, Thailand
    ASEAN Conference on X-ray Absorption Spectroscopy
    July 12-13, 2013
    Spectroscopy on antique Thai glass 1 / 31

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  2. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The gang
    Dr. Wantana Klysubun
    Synchrotron Light Research Instutute
    Nakhon Ratchasima, Thailand
    Dr. G. Lawrence Carr
    BNL, Photon Sciences
    Mag. Dr. Christoph A. Hauzenberger
    Karl Franzens University
    Graz, Austria
    Spectroscopy on antique Thai glass 2 / 31

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  3. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The Grand Palace
    This amazing place is Bangkok’s Grand Palace, the residence of Thai
    royal family.
    The Palace grounds house an important Buddhist site, the Temple of the
    Emerald Buddha (Wat Phra Kaew).
    Spectroscopy on antique Thai glass 3 / 31
    This image is from Wikimedia Commons

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  4. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The Emerald Buddha
    The Temple houses a small statue
    of the Buddha carved from green
    stone.∗
    The story goes that it was carved in the 1st
    century CE in Patna, India. Over two
    millenia, it took a complex path driven by
    Buddhist evangelism, war, and natural
    disaster from India to Sri Lanka, Cambodia,
    Lanna (now in northern Thailand), Laos, and
    finally to the Thai capital, then called
    Rattanakosin (“Keeping place of the Emerald
    Buddha”), in 1784 during the reign of King
    Rama I.
    Today, the statue and its temple are
    both a tourist attractions and a
    sacred Buddhist temple.
    Spectroscopy on antique Thai glass 4 / 31
    This image is from Wikimedia Commons
    ∗jadeite (NaAlSi2O6)

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  5. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The glass mosaic decorations
    Following construction of the Temple in
    the late 18th century, the exterior was
    renovated and decorated with
    innovative, mirrored, glass mosaics
    during the 1830s (under King Rama III).
    The glass was produced at royally
    sponsored glass workshops in Bangkok.
    Here we see a pillar on the rear side of
    the Temple which is still decorated with
    the original glass mosaic.
    Spectroscopy on antique Thai glass 5 / 31
    This image is by me.

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  6. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The glass mosaic decorations
    Here is a closeup of
    the mosaic on that
    column.
    Spectroscopy on antique Thai glass 6 / 31
    This image is by me.

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  7. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The glass mosaic decorations
    Here is a restored
    mosaic using modern,
    commercial glass.
    The modern glass is
    quite different
    visually – brighter,
    more reflective.
    Kind of gaudy, in
    fact.
    Spectroscopy on antique Thai glass 6 / 31
    This image is by me.

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  8. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The red glass sample
    Wantana was asked to explore the prospect of recreating the glass with
    the original formulations for use in future renovations.
    Let’s do chemical analysis and some spectroscopy!
    KMHR1
    from pillar
    shown earlier
    KMSR2
    from elsewhere
    in the temple complex
    The dark bits are oxidized Sn/Pb alloy used for mirroring
    Spectroscopy on antique Thai glass 7 / 31

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  9. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Chemical composition: major elements
    EDX-WDX SEM [wt.%, as oxides]
    KMHR1 KMSR2
    SiO2
    37.99(9) 37.59(77)
    TiO2 < 0.15 < 0.15
    Al2
    O3
    1.41(9) 1.20(13)
    Fe2
    O3
    0.37(5) 0.31(4)
    MnO < 0.15 < 0.15
    MgO 0.53(12) 0.56(11)
    PbO 46.33(103) 51.77(124)
    CaO 0.94(4) 0.90(8)
    Na2
    O 3.86(5) 3.86(14)
    K2
    O 0.78(1) 0.81(3)
    Sum 92.20(103) 97.01(131)
    This glass is heavily leaded – consistent with a refractive index of
    ∼ 1.65
    Spectroscopy on antique Thai glass 8 / 31

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  10. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Chemical composition: minor elements
    LA-ICP-MS [mg/kg]
    KMHR1 KMSR2
    Ti 212(5) 182(11)
    Mn 416(8) 309(19)
    Cu 2204(36) 1883(58)
    Zn 82(2) 78(4)
    As 3234(35) 3616(50)
    Rb 56(2) 50(2)
    Sr 21(1) 18(1)
    Zr 20(1) 16(1)
    Ag 14(1) 13(1)
    Sn 77(3) 59(3)
    Sb 60(1) 56(3)
    Ba 91(1) 82(6)
    Au 45(1) 49(2)
    Several of these elements are
    important to our story:
    1 Cu and As are relevant to the
    optical properties.
    2 Sn and Sb (and possibly As) play
    a role in the redox environment of
    the glass melt.
    3 Au is the central topic of this talk.
    4 The mountain of As plays a big
    role in the XAS measurements.
    Spectroscopy on antique Thai glass 9 / 31

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  11. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    NSLS Beamline X23A2
    We began our X-ray measurements at my beamline
    High energy XRF (12 keV and >29 keV)
    Au K edge XAS
    Spectroscopy on antique Thai glass 10 / 31
    Photo courtesy Jasen Vita, Sarah Lawrence College, and his iPhone.

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  12. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    XRF spectrum
    These glasses are filled with common transition metals – Mn, Fe, Cu –
    as well as a substantial amount of As. Intriguingly, there is a bit of gold
    in these glasses.
    As Kα: 10543 eV Au Lα: 9713 eV
    Spectroscopy on antique Thai glass 11 / 31

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  13. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    What’s the deal with gold?
    Here is a famous, 4th century CE, Roman
    artifact from the British Museum: The
    Lycurgus Cup.
    This is the most famous, ancient example of
    “struck-gold” or “ruby-gold” glass. The red
    color is caused by nanoscale colloidal gold
    finely dispersed throughout the glass matrix.
    Modern recreations of ruby-gold glass
    involve control of the redox potential in the
    melt by addition of SnO2
    . Done correctly,
    this reduces gold salt to colloidal,
    zero-valent gold.
    The punch line of the story
    The 19th century Thai glass craftsmen
    were nanoengineers!
    Spectroscopy on antique Thai glass 12 / 31
    F.E. Wagner, Nature 407 (2000) 691-692.
    DOI: 10.1038/35037661

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  14. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Tin and antimony
    Both tin and antimony are present in the glass.
    Spectroscopy on antique Thai glass 13 / 31

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  15. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Reference measurement
    Reference foil
    Sample
    Four-channel
    ion chamber
    Slit
    assembly
    Incident beam
    Ion chamber
    Fluorescence
    detector
    At X23A2 the angular stability of the mono is poor, so a good reference
    measurement is essential. The glass, however, is too thick to allow
    passage of beam, even at 12 keV. My solution was to use a 20 mm wide
    beam and a special ionization chamber for measuring different regions
    of the swath independently.
    Spectroscopy on antique Thai glass 14 / 31
    B. Ravel et al., J. Synchrotron Rad. (2010). 17, 380-385
    DOI: 10.1107/S0909049510006230

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  16. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Reference measurement
    Reference foil
    Sample
    Four-channel
    ion chamber
    Slit
    assembly
    Incident beam
    Ion chamber
    Fluorescence
    detector
    At X23A2 the angular stability of the mono is poor, so a good reference
    measurement is essential. The glass, however, is too thick to allow
    passage of beam, even at 12 keV. My solution was to use a 20 mm wide
    beam and a special ionization chamber for measuring different regions
    of the swath independently.
    Spectroscopy on antique Thai glass 14 / 31
    B. Ravel et al., J. Synchrotron Rad. (2010). 17, 380-385
    DOI: 10.1107/S0909049510006230

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  17. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Reference measurement
    Reference foil
    Sample
    Four-channel
    ion chamber
    Slit
    assembly
    Incident beam
    Ion chamber
    Fluorescence
    detector
    At X23A2 the angular stability of the mono is poor, so a good reference
    measurement is essential. The glass, however, is too thick to allow
    passage of beam, even at 12 keV. My solution was to use a 20 mm wide
    beam and a special ionization chamber for measuring different regions
    of the swath independently.
    Spectroscopy on antique Thai glass 14 / 31
    B. Ravel et al., J. Synchrotron Rad. (2010). 17, 380-385
    DOI: 10.1107/S0909049510006230

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  18. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Au K-edge XANES
    With the discriminator window set around the Au Lα peak, we measure
    this XANES spectrum. Purple line: Au LIII
    edge energy at 11919 eV.
    Red line: As K-edge energy at 11867 eV.
    Energy (eV)
    Spectroscopy on antique Thai glass 15 / 31

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  19. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Au K-edge XANES
    Here we compare the “Au” data with a properly measured As K-edge
    spectrum from the same sample. It looks much the same, but with some
    excess spectral weight above the Au K-edge energy.
    Energy (eV)
    Spectroscopy on antique Thai glass 15 / 31

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  20. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Au K-edge XANES
    So, we subtract the properly measured As spectrum from the “Au” data,
    resulting in this difference spectrum. These we will treat in the normal
    way, using the indicated pre- and post-edge lines for normalization.
    Energy (eV)
    Spectroscopy on antique Thai glass 15 / 31

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  21. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Au K-edge XANES
    Finally, we see the normalized difference spectrum plotted along with
    transmission XANES from an Au foil. Voil´
    a! Metallic gold is clearly
    present in these glasses.
    So, why is it red?
    This is proof that the gold in the red Thai glass is in the metallic
    form. The XAS does not explain the color.
    Spectroscopy on antique Thai glass 15 / 31

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  22. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    What about the copper?
    Cuprite, CuO2
    , is a brilliant red
    mineral.
    Perhaps the red color in the Thai
    glass comes from Cu1+ ions
    dispersed in the glass.
    Spectroscopy on antique Thai glass 16 / 31
    This image is from Wikimedia Commons.

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  23. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Copper XANES
    Our XANES data demonstrate that
    the Cu is Cu1+ in the glass
    In cuprite, the red color is due∗ to
    an absorption process which
    transfers charge from the O2− ion
    to the Cu1+ ion. However, in glass,
    Cu has a filled d band, so there is
    no available transition.
    KMHCL2 is a piece of clear glass
    of the same vintage.
    Cu is not the colorant.
    Spectroscopy on antique Thai glass 17 / 31
    ∗See The Physics and Chemistry of Color by Kurt Nassau. These data measured at SLRI BL8 −

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  24. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    A bit of history
    James Clerk Maxwell Garnett (b. 1880)
    was a junior research fellow at Trinity
    College, Cambridge when, in 1904, he
    authored a seminal paper explaining
    coloration in metals and metal glasses.
    After a brief career as a mathematical
    physicist, he became an academic
    administrator, then lead Britain’s
    League of Nations Union. Britain along
    with Thailand (under King Rama VI)
    were among the founding members of
    the LN.
    Photograph of J.C.M. Garnett in the National Portrait Gallery (London)
    Spectroscopy on antique Thai glass 18 / 31

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  25. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Garnett’s seminal paper
    “Colours in Metal Glasses and in
    Metallic Films”, Philosophical
    Transactions of the Royal Society of
    London, 203 (1904), p. 385.
    This journal begun publication in 1665.
    Isaac Newton published “New Theory
    about Light and Colours” in 1672.
    Volume 203 also included an article on
    acoustics by Lord Rayleigh, the same
    Lord Rayleigh for whom elastic
    scattering of photons is named.
    Spectroscopy on antique Thai glass 19 / 31

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  26. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    For decades his work languished...
    ... then along came nanotechnology and the ability to resolve objects on
    the scale of 10s of nanometers.
    Spectroscopy on antique Thai glass 20 / 31

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  27. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    NSLS Beamline U10B
    Use the synchrotron
    optical, near IR, and near
    UV spectrum
    Bruker FTIR spectrometer
    with CaF2
    vis/UV
    beamsplitter
    Si and GaP photodiode
    detectors
    Transmission spectroscopy
    at near-normal incidence
    Analyze as absorbance
    A = -log(Transmission)
    Spectroscopy on antique Thai glass 21 / 31
    Photo from the U10B webpage

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  28. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Garnett theory for optical properties of
    heterogeneous materials
    E
    applied
    p = α·E
    When an electric field is applied to an atom of polarizability α, a dipole
    is created.
    Spectroscopy on antique Thai glass 22 / 31

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  29. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Garnett theory, cont.
    E
    applied
    An electric field applied to a solid
    results in an array of dipoles.
    Macroscopic optical response given
    by the dielectric function
    ε(ω) ≡ ε (ω) + iε (ω)
    and the refractive index n = e1/2
    E
    applied
    E
    local
    The local electric field at any point
    in the solid includes the induced
    fields of the surrounding dipoles.
    Spectroscopy on antique Thai glass 23 / 31

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  30. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Garnett theory, cont.
    E
    applied
    E
    local
    The Clausius-Mossotti relation
    connects macroscopic dielectric
    response ε with the polarizability α
    of the individual atomic (or
    molecular) components.
    ε−1
    ε+2
    = 4π
    3

    Spectroscopy on antique Thai glass 24 / 31

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  31. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Garnett theory, cont.
    E
    applied
    E
    local
    ε
    particle
    Generalized form for polarizable components embedded in an existing
    dielectric εb
    .
    εeff−εb
    εeff+εb
    = 4π
    3

    Spectroscopy on antique Thai glass 25 / 31

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  32. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Garnett theory, cont.
    Let polarizable entities be spherical inclusions of radius
    a 1 and having dielectric response εinc
    inside host
    material of εhost
    .
    α = εinc −εhost
    εinc
    +εhost
    ·a3
    Substitute and solve for
    εeff
    . This is Garnett’s
    dielectric response for a
    composite.
    εeff
    = εhost
    + εinc
    3f (εinc −εhost
    )
    (1−f )(εinc −εhost
    )+3εhost
    Assume that the inclusion is dilute, f 1, and solve for the absorption
    coefficient:
    A(ω) =2ωc−1 Im ε(ω)
    =
    18f ω2ε1.5
    host
    c2
    εinc
    (εinc
    + 2εhost
    )2 + (εinc
    )2
    There is a resonance when εinc
    = −2εhost
    Spectroscopy on antique Thai glass 26 / 31

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  33. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Dielectric response for gold
    Glass with n ≈ 1.5 has εglass ≈ 2.25
    So gold in glass has a resonance when
    εAu
    ≈ −4.5.
    That happens at about 2.3 eV.
    Spectroscopy on antique Thai glass 27 / 31
    P.B. Johnson and R.W. Christy, Phys. Rev. B 6, 4370-4379 (1972)
    DOI: 10.1103/PhysRevB.6.4370

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  34. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Optical spectroscopy
    0
    0.5
    1
    1.5
    2
    2.5
    1 1.5 2 2.5 3 3.5
    1033 774 619 516 442 387
    Optical density (a.u.)
    Energy (eV)
    Wavelength (nm)
    GaP
    Si
    Garnett
    Infrared
    Ultraviolet
    The red and blue traces show the absorption of light by the glass.
    The purple trace is the predicted absorption by 30 nm Au spheres in glass
    using J.C.M. Garnett’s theory.
    Other elements (Fe and As) cause strong absorption in the ultraviolet.
    Yellow, green, blue, and violet are absorbed. Red transmits.
    Green light is absorbed due to the gold. Gold → red, no gold → green
    Spectroscopy on antique Thai glass 28 / 31

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  35. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    The proof of the pudding...
    Wantana is working on recreating the antique glass
    This is glass she made with the
    chemical composition of the original
    red glass, but without gold.
    This glass has the chemical
    composition of antique clear glass,
    but with 0.1 wt% AuCl3
    and 0.2 wt%
    Sb2
    O3
    . The color is not quite right,
    but close!
    Spectroscopy on antique Thai glass 29 / 31

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  36. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    We’re making progress!
    Yellow and clear
    Published∗
    Red Ready to submit†
    Blue and green
    Forthcoming
    Learning how to blow
    and flatten the glass,
    then cut it into tiles
    will be another story
    entirely!
    Spectroscopy on antique Thai glass 30 / 31
    ∗W. Klysubun, et al. Applied Physics A 11:3 (2013), pp 775-782, DOI: 10.1007/s00339-013-7657-8
    †will be submitted to Spectrochimica Acta

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  37. The Temple Samples X-ray measurements XAS Optical spectroscopy Conclusion
    Questions for an art historian
    1 What is the source of the lead? Perhaps galena (PbS). Knowing this
    would help understand the origin of the various impurities.
    2 How was the reductant introduced? Was Sn or Sb introduced directly? Or
    as an impurity of some other constituent?
    3 What is the source of the gold? AuCl3
    is unlikely for the time period.
    Perhaps chloroauric acid (HAuCl4
    ), the product of dissolving gold in aqua
    regia, was used.
    4 What blowing and cutting techniques were used?
    5 How did the Thai craftsmen know about the ruby-gold technique? Via
    contact with Europe (where it was rediscovered in the late 17th century)?
    Via contact with China? Independent discovery?
    Spectroscopy on antique Thai glass 31 / 31

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