Solid state NMR investigation of the roman Acqualadroni rostrum: tenth year assessment of the consolidation treatment of
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ORIGINAL RESEARCH
Solid state NMR investigation of the roman Acqualadroni rostrum: tenth year assessment of the consolidation treatment of the wooden part Alberto Spinella . Delia Francesca Chillura Martino . Maria Luisa Saladino Federica Sammartino . Francesco Caruso . Eugenio Caponetti
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Received: 1 April 2020 / Accepted: 29 October 2020 Ó Springer Nature B.V. 2020
Abstract This work follows a previous one dealing with the state of conservation study of the wooden part of the roman Acqualadroni rostrum soon after its finding in the seabed of Acqualadroni (Messina, Italy). The archaeological survey and recovery were particularly relevant since this artefact is one of the two rostrums, nowadays known, found together with its wooden part. Following the recovery, it was consolidated by immersion in a melamine-formaldehyde resin (Kauramin) aqueous solution for eight months at the ‘‘Centro di Restauro del Legno Bagnato’’ (Pisa, Italy). The present investigation is aimed to determine at microscopic scale the wood state of conservation and to highlight interactions of the consolidant with wood components, by using solid-state NMR spectroscopy ten years after the consolidation treatment.
Sampling by coring was exceptionally authorized, and the wood core was divided into seven aliquots as a function of depth. 13C cross-polarization magic angle spinning (13C{1H} CP-MAS NMR) spectra and variable contact time (VCT) experiments have been carried out to determine the cellulose crystallinity index, the lignin condensation degree and the holocellulose-lignin ratio. The interactions between the resin and the wood components were highlighted by T1qH relaxation times determination and two-dimensional 13C–1H correlation (FSLG CP HETCOR) NMR experiments. Findings revealed specific interactions between the aromatic part of the resin and the lignin, as well as a network of hydrogen bonds involving all components of the system.
A. Spinella (&) Advanced Technologies Network Center (ATeN Center), Universita` degli Studi di Palermo, Via F. Marini, 14, 90128 Palermo, Italy e-mail: [email protected] D. F. Chillura Martino M. L. Saladino F. Sammartino E. Caponetti Dipartimento STEBICEF, Universita` degli Studi di Palermo, Viale delle Scienze ed. 17, 90128 Palermo, Italy F. Caruso Abteilung Kunsttechnologie, Schweizerisches Institut fu¨r Kunstwissenschaft (SIK-ISEA), Zollikerstrasse 32, 8032 Zu¨rich, Switzerland
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Cellulose
Graphic abstract
Keywords Conservation treatment Waterlogged wood Microscopic structure Melamineformaldehyde resin Introduction A waterlogged wood structure can undergo profound changes as a result of the biotic and abiotic degradation processes (Kim et al. 2016; Blanchette et al. 1994). In particular, the leaching of hemicelluloses, the hydrolysis, and oxidation of cellulose with consequent depolymerization of cell wall components and leaching of soluble compounds can cause the formation of pores. Notwithstanding, at low temperature, low UV-irra
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