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.
© Copyright 2025 ExpyDoc