Non-destructive spectroscopies on fragments found in Sana’a (Yemen): evidence of different
recipes for iron tannic inks.
Marina Bicchieri1*, Michela Monti1, Giovanna Piantanida1, Armida Sodo1,2
1
Istituto centrale per la conservazione e il restauro del patrimonio archivistico e librario,
laboratorio di chimica. MiBAC, Via Milano 76, 00184 Roma Italy. Tel: +39 0648291217, Fax:
+39 064814968, e-mail: [email protected] ; [email protected] .
2
Università di Roma Tre, Via della Vasca Navale 84, 00146, Roma, Italy.
Keywords: Micro-Raman, ATR-FTIR, XRF, tannic inks
Abstract
Six fragments from different manuscripts (three fragments on membranaceous substrate, three on
paper) were analyzed by means of ATR-FTIR, Micro-Raman and XRF spectroscopies. The
combination of such elemental and molecular techniques allowed characterization of conservation
state of all fragments, identification of sizing agents on paper fragments and of all red and black
writing media composition. Black inks analysis, in particular, provided interesting insight:
independently of the substrate, in fact, all inks seem to have identical composition, corresponding
to high-quality iron-tannic inks, not added with carbon black and rather well preserved. However,
the tannate residual Raman peaks, in some samples, appears definitely shifted with respect to the
ones typically found and reported for iron-gall tannic inks1,2, whereas the other spectral features are
well matched (Figure 1). The same shifts are less recognizable in the ATR-FTIR spectra, due to
superimposition, in the 1500-1700 cm-1 range, to peaks belonging to parchment or gelatin (used as
sizing agent in most samples). The hypothesis was made, in order to explain the phenomenon, that
the ink had been manufactured by extracting tannin from plant materials other than gallnuts.
Research is ongoing on laboratory samples, aiming at comparing vibrational spectra of tannins
extracted from vegetation mostly common in the Mediterranean and Middle-Eastern area, and the
first results positively show that different species produce different features in the tannin spectra.
On the pure extract, the phenomenon is visible both by Raman and FTIR (Figure 2).
Raman Intensity [arbitrary units]
10000
A
B
C
5000
D
0
200
400
600
800
1000
1200
1400
1600
Wavenumber [cm -1 ]
Figure 1: Raman spectra of A) Fragment n.4; B)
Iron-gall tannic ink; C) Fragment n.6; D) Fragment n.5
.
Figure 2: FTIR spectra of tannins extracted from A)
Prunus cerasifera; B) Rhus coriaria; C) Quercus
macrolepis; D) Castanea sativa
Conclusions
Research on the spectral features of tannic-inks, other than providing information on the exact
composition of the specific inks applied in these fragments, could improve knowledge of the iron
inks manufacturing methods, and possibly indication of the geographical areas where these
methods were most likely in use.
References
1. A.S. Lee, P.J. Mahon, D.C. Creagh. Vib. Spectrosc. 2006; 41: 170-175.
2. M. Bicchieri, M. Monti, G. Piantanida. and A. Sodo. J. Raman Spectrosc 2008; 39: 1074–1078.