Raman Spectroscopic Library

Raman Spectroscopic Library of Natural and Synthetic Pigments
Ian M. Bell, Robin J.H. Clark and Peter J. Gibbs Christopher Ingold Laboratories
University College London, 20 Gordon Street, London WC1H 0AJ, UK

The authors' research in this field was reported in the 21/2/98 edition of the New Scientist magazine, and one of their research papers has been selected as a 'Hot Article' for February 1998 by the American Chemical Society.

Click on the logo to access the relevant internet publications.

Introduction to the site

Raman microscopy is now established as the technique that is most specific, sensitive, spatially refined and immune to interference for the non-destructive, in situ analysis of historical artefacts. To complement the increasing use of the technique in this field, the Raman spectra of sixty-four common pigments, both natural and synthetic, known to have been in use before ~1850 AD, have been studied by Raman microscopy.
Fifty-six pigments have yielded high quality spectra and these have been arranged here, by colour, into a spectroscopic library for reference purposes.

	The pigment data have been arranged by colour into seven tables which can be accessed by clicking on the relevant link: black, blue, green, orange, red, white and yellow. The eight pigments that failed to give adequate spectra at either of the excitation lines used are included in a separate table. The spectra may be viewed by activating the link on the name of the pigment.
	Spectroscopic files in SPC format may be downloaded via the spectra pages. They may be viewed in many spectroscopic software packages including Omnic (Nicolet Instruments: http://www.nicolet.com) and GRAMS/32 (Galactic Industries). A free viewer for SPC files, SPCView, may be downloaded from the Galactic Industries web page at http://www.galactic.com.
	Warning Before you proceed, please note that the wavenumbers quoted in the tables were obtained from spectra calibrated with Neon lines. We anticipate that the wavenumbers are accurate to ± 1 cm^-1, except for bands marked as broad (br) or shoulder (sh) in the table. However, the SPC files have not yet been corrected and the band positions in the downloadable spectra may differ from those in the table.
USERS NOTE Some users have experienced difficulty with the downloadable SPC files. The downloaded spectra have a gross non-linear distortion of the x-axis, which is nothing to do with the uncorrected band positions (see above statement). The SPC files have now been reloaded and are downloading correctly at our end. If any user experiences further problems, please contact the Webmaster. Thank you. 29th May 1998
	Some Raman literature references to the pigments have been provided and clicking the link on the numbers in the tables can access these. To reference the authors' publications in the field of archaeometric analysis click here

Table of Black Pigments

Name

Composition

Band Wavenumbers^a / cm^-1 and Relative Intensities^b

Excitation Wavelength & Power

Notes and Date^c

ivory black

carbon

961m (=n₁(a₁) PO₄^3-); ~ 1325vs(br); ~ 1580vs(br)

632.8 nm
6 mW

Antiquity. Also contains calcium phosphate

lamp black

carbon

~ 1325vs(br); ~ 1580vs(br)

632.8 nm
6 mW

Antiquity

^a Approximate centres of broad bands in the laser fluorescence spectrum.
^b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
^c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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