Scientific Examination of Art Modern Techniques in Conservation and Analysis (2005) / Chapter Skim
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Raman Microscopy in the Identification of Pigments on Manuscripts and Other Artwork--Robin J. H. Clark
Raman Microscopy in the Identification of Pigments on Manuscripts and Other Artwork--Robin J. H. Clark
Pages 162-185
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From page 162... ...
H Clark Christopher Ingold Laboratories University College London London The identification of pigments on manuscripts, paintings, enamels, ceramics, icons, polychromes, and papyri is critical in finding solutions to problems of restoration, conservation, dating, and authentication in artwork, and many techniques (molecular and elemental)
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From page 163... ...
all restoration should be carried out with the original pigment and not with alternatives of similar hue; this is important since some alternatives might be liable to react with contiguous pigments with deleterious visual effects or (b) restoration with a different pigment might be desirable owing to instability of the original one or because it is more desirable to restore with carefully documented and easily identifiable nonoriginal pigment, possibly modern.
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From page 164... ...
, and proprietary literature. By way of illustration, the commonly used blue inorganic pigments are listed in Table 1, together with their chemical names, formulas, provenance, and an indication as to the nature of the electronic transitions principally responsible for the blue color in each case.
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and/or the date of its first manufacture is listed. bLF = ligand field; CT = charge transfer; IVCT = intervalence charge transfer transition.
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From page 166... ...
Although the use of a beamsplitter reduces the overall efficiency of the system, as does the use of a pinhole as a spatial filter, both devices restrict the amount of unwanted scattered light collected from outside the focus of the laser beam. The benefit of a pinhole is that it ensures a good confocal arrangement, thereby providing spatial resolution as a function of sample depth.
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From page 167... ...
available in order to search for the most enhanced Raman spectrum, bearing in mind the often opposing effects on the scattering intensity of 4 (the fourth power of the frequency of the scattered light) , absorption, resonance, and possible photochemical and/or thermal degradation of the sample.
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Raman microscopy is considered by many to be the best single technique for this purpose and is extremely effective when used in conjunction with other complementary techniques, such as polarized light microscopy (PLM) , infrared microscopy (IR)
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From page 169... ...
Western Manuscripts Early Raman studies of a Paris Bible of ca 1275 in Latin rapidly revealed the ease with which most inorganic pigments may be distinguished, even with Raman microscope systems of a 1980s design (Best et al., 1992, 1993)
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, respectively, possibly owing to the lack of lead ores in Iceland. Extensive studies have now been carried out on many manuscripts and codices in the British Library, the Victoria and Albert Museum, the Museum of London, the Beinecke
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. These are brilliantly illuminated codices, the red, green, blue, white, and black pigments on the King George III Bible consisting of vermilion (HgS)
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Cuthbert, who was bishop of Lindisfarne in Northumbria during the period 685-687, the major pages display fantastic complexity of zoomorphic and interlace ornament, by contrast to the simplicity of the evangelist portraits. The most important result of the early pigment analyses of the Gospels by light microscopy was thought to be the apparent identification (Roosen-Runge and Werner, 1960)
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173 RAMAN MICROSCOPY IN THE IDENTIFICATION OF PIGMENTS FIGURE 4 Initial page of the Gospel of St.
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by light optimally in the wavelength range 530-560 nm is of great interest. The conversion occurs naturally in sunlight and was apparently recognized in Mesopotamia even as early as 1220, when pararealgar was applied to the above lectionary as a yellow pigment in addition to, and in distinctly different places from, the much more common yellow pigment orpiment, As2S3 (Clark and Gibbs, 1998b)
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Figure 5 shows a painting -- considered by art historians to be from the late 17th century and Dutch -- of a young woman with red ribbons in her hair, a pearl necklace, and a cream-coloured skirt beneath a yellow shawl. The pigments (vermilion, lazurite, and lead tin yellow Type I, particularly the last two)
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From page 176... ...
of the pigments on Egyptian faience of the XVIIIth dynasty (ca 1350 BC) recovered in 1891 from the Nile Valley by Sir William Flinders Petrie and held at the Petrie Museum, University College London, has revealed that the red shards are pigmented with red ochre/red earth and the brilliant yellow shards with lead antimony yellow (Pb2Sb2O7)
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From page 177... ...
ICONS AND POLYCHROMES The combined application of Raman spectroscopy and LIBS has proved to be very effective for the identification of pigments at different depths below the surfaces of icons and polychromes. LIBS is an atomic emission technique in which an intense nanosecond laser pulse onto the surface of the sample results in the formation of plasma which, upon being allowed to cool, emits radiation characteristic of the elements present.
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178 SCIENTIFIC EXAMINATION OF ART FIGURE 7 Nineteenth-century Russian icon of St. Nicholas held in Greece on which studies by LIBS and Raman microscopy enabled depth profile analyses of the pigments to be made (Burgio et al., 2000)
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from the Tapling Collection at the British Library were shown to have been printed using Prussian blue, Fe4[Fe(CN)
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. Many more Raman studies of the pigments and pigment degradation products on frescos and on wall paintings in caves are likely to be made with the effective development of mobile Raman systems (Clark and Gibbs, 1998a)
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Detailed Raman studies have also been carried out on millimetre-sized single crystals of PbS, a model material for quantum dot research, under resonance Raman conditions, and the phonon modes identified and assigned (Smith et al., 2002b)
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1, f. 33v, of the Jamnitzer manuscript at the Victoria and Albert Museum, London, in which the original highlights of lead white have degraded to lead sulfide (black)
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van der Weerd, and to Renishaw PLC, the Engineering and Physical Sciences Research Council, the European Union, and the British Library for their support of this research.
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From page 184... ...
2004. Journal of Raman Spectroscopy 35:279-283.
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From page 185... ...
2004. Journal of Raman Spectroscopy 35:119-124.
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