Poster 14 [pdf] - CHEMCH2014: Academy of Fine Arts, Vienna, July

Examination of Historic Parchment Manuscripts by Non-invasive
Reflection-FTIR – Possibilities and Limitations
W. Vetter, G. Pöllnitz, M. Schreiner
Institute of Science and Technology in Art (ISTA), Academy of Fine Arts,
Schillerplatz 3, 1010 Vienna, Austria
[email protected]
Introduction
Since ancient times, parchment has been used as support for manuscripts. As it shows a relatively high
durability, many old parchment objects can be found in libraries and museums. Nevertheless, both
religious and secular manuscripts often have been used extensively over centuries or were kept in
suboptimal environmental conditions and hence signs of wear and degradation must be noticed in many
cases. In our poster we report several results obtained by non-invasive reflection-FTIR and complementary XRF analysis of parchments and writing materials on manuscripts from the 13th and 15th century.
FTIR has been used for damage assessment of parchment as well as for the characterization of inks and
pigments on manuscripts mainly applied in transmission- or ATR-mode. However, only few studies utilized
non-invasive approaches. We found that reflection-FTIR is a useful tool for the identification of superficial
contents of salts e.g. calcium carbonate, calcium soaps, calcium oxalate or basic copper(II) carbonate
(azurite), whereas damage assessment was limited mainly by interference of parchment bands with
calcium carbonate and calcium soaps as well as strong inhomogeneity of the analyzed parchments.
Experimental
Reflection-FTIR instrument:
measuring point
Procedure:
spectrometer
Spectrometer ALPHA - external reflection (Bruker Optics, Ettlingen, Germany)
Measurements
Parameters:
Source:
Globar
Range:
4000-375 cm-1
Detector:
DTGS
Resolution:
4 cm-1
Spot size:
ca. 4 mm
Scans:
64-128
Geometry:
20°/20°
Software:
OPUS 6.5
Kramers-Kronig transform
(KKT)
Reflection spectra
Absorption index spectra
Evaluation
Transmission databases: IRUG (www.irug.org)
manuscript
Objects:
Glagolitic manuscripts: 13th century (Croatian Academy of Sciences and Arts,
Measuring system:
Spectrometer + self built stand + lifting platform (Fig.1)
Zagreb, Croatia & National Széchényi Library of Hungary, Budapest).
lifting platform
Precise adjustment of the accurate measuring distance, selection and
documentation of measuring is enabled by a built in camera.
Tyrolean manuscript: Oswald von Wolkenstein, manuscript B, 15th century
Fig.1:
rFTIR-measurements
of
manuscripts
(National Library of Hungary, Budapest).
(University and State Library for Tyrol , Innsbruck)
Results and Discussion
Comparison of reflection-FTIR, transmission-FTIR and ATR-FTIR:
Damage assessment of parchments:
A parchment reference (calf, National Research and Development Institute for Textiles and Leather,
Bucharest, Romania - INCDTP-ICPI) was analyzed by FTIR in either reflection-, transmission- or ATRmode. The characteristic protein absorption bands are assigned in Tab.1. Kramers-Kronig transform
(KKT) of the reflection spectra allowed a comparison to the other techniques, although certain band shifts
could be observed (Fig.2, Tab.2). The diameter of the analyzed area was 4 mm (reflection), <2 mm
(ATR) and 0,1 mm (transmission-FTIR-microscopy) which should be considered in case of parchment
inhomogeneity.
An evaluation of parchment degradation by examination of the positions and intensities of Amid I (ca.
1650 cm-1) and Amide II bands (ca. 1550 cm-1) was reported by Derrick.[1] Hydrolytical damage was
assessed by the ratio of Amide I to Amide II (AI/AII) and denaturation by a shift of Amide II to lower
wavenumbers (AI-AII). In our studies, determination of Amide II often was impossible due to band
interference with calcite and/or calcium soaps (Fig. 3) from the surface of the manuscripts. Calcite is
most probably derived from the manufacturing process, whereas the origin of calcium soaps remains
unclear (cleaning process?).
3080
N-H stretching
Amide A
N-H bending
overtone
Amide B
ATR-FTIR
Amide A
1650
C=O stretching
Amide I
1550
N-H bending &
C-N stetching
Amide II
Amide I
*
877 cm-1
3320
1453 cm-1
[cm-1]
1580 cm-1
Wavenumber Band assignment
GF2_folio 1 recto mp03, KKT
Ca-stearate
IRUG OF0108
GF1_folio 1 verso, mp01, KKT
parchment reference
calf, KKT
calcite IRUG MP0108
1544 cm-1
calf parchment
calf parchment reference
reflection-spectrum
1412 cm-1
Tab.1:
Characteristic protein absorption bands
trans.-FTIR
Amide B
Amide II
reflection-FTIR
Kramers-Kronig transform
Tab.2:
Measuring technique / Amide I and II
Amide I
[cm-1]
Amide II
[cm-1]
reflection
1660
1556
trans.*
1645
1553
ATR
1629
1540
Fig.2: Left – reflection-spectrum (blue) and the corresponding absorption indexspectrum (red) from reference calf parchment. Right – comparative measurements of
the reference parchment by use of different FTIR-techniques yielded relatively similar
results, except for Amide I and II (see Tab.2).
*Even though spectral resolution was 4 cm-1 in all cases, Amide I showed three
maxima at 1660, 1650 and 1645 cm-1 (highest max.) – influence of water?
Fig.3: Band interference of Amide II (ca. 1650 cm-1) with calcite (left, measuring
point on folio 1 recto, fragment GF1, Zagreb) or calcium soaps (right). As it was
observed in previous measurements on mockups,[2] the maximum of the asymmetric
stretching band of CO32- in the KKT-spectrum was shifted to higher wavenumbers
compared to the transmission reference. The strong band at ca. 1040 cm-1 (*) in
spectrum from the measuring point (left side) most probably derives from a silicate
material (abrasive, dirt?).
measuring point (mp)
Fig.4: Folio 1 recto of the Glagolitic
manuscript GF2 (Croatian Academy of
Sciences and Arts, Zagreb, Croatia).
Pigments in manuscripts:
Dark brown/ black inks:
Blue azurite (Cu3(CO3)2(OH)2) was identified in the Tyrolean manuscript (Fig.5) by reflection-FTIR (Fig.6, left)
as well as Cu detection by XRF. As described[3] the reflection spectrum is strongly influenced by the
Reststrahlen effect. In red areas, detection of Hg proved that cinnabar was used, which does not absorb
MIR in the spectral range evaluated. Red pigment based inks were also used in the Glagolitic manuscripts
which contained cinnabar as well. Most probably effected by a scattering effect at cinnabar particles, the
Amide I and II bands were slightly attenuated at several red measuring points (Fig.6, right).
The materials of the dark brown/black inks could not be identified. Although the results obtained by XRF
indicate the use of iron gall ink (Fe contents), no evidence for gallotannic acid or FeSO4 was found by
reflection-FTIR. The spot size of ca. 4 mm did not allow to measure areas entirely covered with ink.
Nevertheless, Amide I and II bands at ink measuring points often appeared broader and not as well
defined compared to parchment areas (Fig.6, left). Furthermore, calcium oxalate was detected in areas
with black ink in the Tyrolean manuscript, probably a metabolite of mold fungi (Fig.6, right).
mp01 parchment, KKT
mp08 red, KKT
parchment, mp02, KKT
black ink, mp09,
reflection
Amide I
Fig.5: Folio 1 recto of the Tyrolean
manuscript (University and State
Library for Tyrol , Innsbruck).
Amide II
Amide II
calcium oxalate IRUG MP0424
mp08
mp01
black ink, mp09, KKT
black ink, mp03, KKT
Amide I
838 cm-1
955 cm-1
3430 cm-1
1425 cm-1
mp12 blue, reflection
azurite IRUG MP0001
1670 cm-1
1643 cm-1
1643 cm-1
Fig.6: Left – most of the bands in the reflection-spectrum (blue) were inverted due to
the Reststrahlen effect and are located at similar wavenumbers to azurite reference
IRUG MP0001 (black) measured in transmission. Right – the comparison of the KKTspectrum from mp01 parchment (black) and mp08 red (red) illustrates a slight
attenuation of Amide I and II.
Literature
1. M. Derrick. Evaluation of the State of Degradation of Dead Sea Scroll Samples Using FT-IR Spectroscopy. The American Institute
for Conservation, The Book and Paper Group Annual, Vol. 10, 1991.
2. W. Vetter, M. Schreiner. “Characterization of Pigment-Binding Media Systems - Comparison of Non-Invasive In-Situ Reflection
FTIR with Transmission FTIR Microscopy.“ e-PRESERVATIONScience 8, 2011: 10-22.
3. F. Rosi et al., “Non-Invasive Identification of Organic Materials in Wall Paintings by Fiber Optic Infrared Spectroscopy: A
Statistical Approach.” Anal Bioanal Chem (2009) 395: 2097-2106.
Fig.6: Left – comparison of spectra obtained from a parchment area (red) and partially covered with ink (black) on a manuscript
from the National Library of Hungary, Budapest (BF_folio 8a recto). Right – the C=O stretching band from calcium oxalate in the
spectrum from mp09 with black ink on folio 35 recto in the Tyrolean codex appeared inverted with maxima at a similar wavenumber
(1643 cm-1) as in the absorption reference spectrum measured in transmission (1670 cm-1 in the KKT-spectrum!).
Conclusion
Our results showed that reflection-FTIR is a suitable method to identify salts and pigments on the surface
of parchments and illuminated manuscripts rather than for damage assessment of the parchment or the
characterization of black inks used in history. Kramers-Kronig transform of the reflection spectra yielded
satisfactory results in many cases and allowed a reliable interpretation of the spectra obtained using
transmission databases. In contrast, azurite was identified by evaluation of the reflection spectrum which
was strongly influenced by the Reststrahlen effect resulting in inverted bands at similar positions as in the
transmission reference spectrum.

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