Date of study: March 11–12, 2013
A research team at Columbia University consisting of Professor James T. Yardley of the Department of Electrical Engineering and Alexis Hagadorn, Head of Conservation, Columbia University Libraries, with the support of Dr. David Ratzan, Curator of the Papyri Collection, has utilized micro-Raman spectroscopy to investigate the chemical composition of pigments for selected regions on both sides of the manuscript fragment known as the Gospel of Jesus's Wife (GJW) and also for an additional fragment from the Gospel of John. These manuscripts were provided for the purposes of this study through Professor Karen King of Harvard University. Most dyes or pigments exhibit characteristic Raman spectra.18 Micro-Raman spectroscopy constitutes a non-destructive technique for characterizing the chemical composition of inks and pigments.19 In the Raman scattering process molecules within the exciting laser beam emit light with photon energy reduced (and therefore wavelength increased) by the amount of a characteristic vibrational motion of the molecule. Therefore the measurement of scattered light intensity as a function of wavelength provides direct information about the inks under investigation through the display of characteristic vibrational resonances or peaks. Black ink pigments generally fall into the categories of carbon black (many variations),20 iron gall,21 hematite,22 magnetite,23 and various iron oxides.24 Modern black inks are formulated using complex dye molecules that typically exhibit characteristic sharp spectral features.25 For black pigments based on forms of carbon black, the detailed spectral characteristics are somewhat dependent on specific pigment preparation as well as excitation wavelength.
For these manuscripts, we obtained micro-Raman spectra using a conventional commercial instrument (Renishaw inVia). We used 633 nm laser excitation (10 mWatt maximum power) using 0.5%–10% of the laser power focused onto the sample through a conventional ×100 microscope objective. We collected approximately 140 Raman spectra from selected regions of the two sides of the two manuscripts, examining in detail the Raman shift range from 150 cm−1 to 1900 cm−1. In a parallel study we have examined Raman spectra from over fifteen papyrus manuscripts from the Columbia collection covering the time period from 500 b.c.e. to +1000 c.e.26 The conclusions of this study for the GJW manuscript are as follows:
1) The inks used in this manuscript are primarily based on carbon black pigments such as “lamp black.” The observed Raman spectra are very similar to those of the carbon-based inks studied for a wide variety of manuscripts including many dating from the early centuries of the Christian era.
2) From the observed Raman spectra, we find no evidence for any constituents of ink or types of ink other than carbon black in the selected regions.
3) The ink or inks used in GJW are similar to, but distinct from, the ink used for the Gospel of John manuscript.
4) Within the available accuracy of our measurements, our data are consistent with a single ink composition for each individual side of the GJW manuscript.
5) The Raman spectra obtained from the “recto” side and from the “verso” side are indistinguishable within our experimental error.
18 Clark, Robin J. H., “Pigment Identification on Medieval Manuscripts by Raman Microscopy,” Journal of Molecular Structure 347 (1995) 417–27; idem, “Pigment Identification by Spectroscopic Means: An Arts/Science Interface,” Comptes Rendus Chimie 5 (2002) 7–20; Smith, Gregory D. and Clark, Robin J. H., “Raman Microscopy in Archaeological Science,” Journal of Archaeological Science 31 (2004) 1137–60; Burgio, Lucia, Clark, Robin J. H., and Hark, Richard R., “Raman Microscopy and X-ray Fluorescence Analysis of Pigments on Medieval and Renaissance Italian Manuscript Cuttings,” Proceedings of the National Academy of Sciences of the United States of America 107 (2010) 5726–31.
19 Bell, Ian M., Clark, Robin J. H., and Gibbs, Peter J., “Raman Spectroscopic Library of Natural and Synthetic Pigments (pre- Approximately 1850 AD),” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 53 (1997) 2159–79; Burgio, Lucia and Clark, Robin J. H., “Library of FT-Raman Spectra of Pigments, Minerals, Pigment Media and Varnishes, and Supplement to Existing Library of Raman Spectra of Pigments with Visible Excitation,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 57 (2001) 1491–521.
20 Tomasini, Eugenia P.et al., “Micro-Raman Spectroscopy of Carbon-Based Black Pigments,” Journal of Raman Spectroscopy 43 (2012) 1671–75.
21 Lee, Alana S., Mahon, Peter J., and Creagh, Dudley C., “Raman Analysis of Iron Gall Inks on Parchment,” Vibrational Spectroscopy 41 (2006) 170–75; Lee, Alana S., Otieno-Alego, Vincent, and Creagh, Dudley C., “Identification of Iron-Gall Inks with Near-Infrared Raman Microspectroscopy,” Journal of Raman Spectroscopy 39 (2008) 1079–84; Bicchieri, Marinaet al., “All That is Iron-Ink is Not Always Iron-Gall!,” Journal of Raman Spectroscopy 39 (2008) 1074–78; Bicchieri, Marinaet al., “Non-Destructive Spectroscopic Investigation on Historic Yemenite Scriptorial Fragments: Evidence of Different Degradation and Recipes for Iron Tannic Inks,” Analytical and Bioanalytical Chemistry 405 (2013) 2713–21.
22 David, A. Rosalieet al., “Raman Spectroscopic Analysis of Ancient Egyptian Pigments,” Archaeometry 43 (2001) 461–73.
23 Slavov, Lubomiret al., “Raman Spectroscopy Investigation of Magnetite Nanoparticles in Ferrofluids,” Journal of Magnetism and Magnetic Materials 322 (2010) 1904–11.
24 Bikiaris, Dimitriset al., “Ochre-Differentiation through Micro-Raman and Micro-FTIR Spectroscopies: Application on Wall Paintings at Meteora and Mount Athos, Greece,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 56 (2000) 3–18.
25 Abbott, Laurence C.et al. “Resonance Raman and UV-Visible Spectroscopy of Black Dyes on Textiles,” Forensic Science International 202 (2010) 54–63; Geiman, Irinaet al. “Application of Raman Spectroscopy and Surface-Enhanced Raman Scattering to the Analysis of Synthetic Dyes Found in Ballpoint Pen Inks,” Journal of Forensic Sciences 54 (2009) 947–52; Littleford, Racheal E.et al., “Surface-Enhanced Resonance Raman Scattering of Black Inkjet Dyes in Solution and in Situ Printed onto Paper,” Applied Spectroscopy 57 (2003) 977–83; Womack, James D., Vickers, Thomas J., and Mann, Charles K., “Determination of Azo Dyes by Resonance-Enhanced Raman Spectroscopy,” Applied Spectroscopy 41 (1987) 117–19.
26 We thank Michael Ryan, head of the Columbia Rare Book and Manuscript Library, for making these papyri available.