Proceedings e report - Firenze University Press

CHARACTERIZATION OF WATERLOGGED WOOD BY INFRARED
SPECTROSCOPY
Benedetto Pizzo 1 *, Ana Alves 2 , Nicola Macchioni 1 , Antonio Alves 2 , Gianna Giachi 3 ,
Manfred Schwanninger 4 , José Rodrigues 2
1 CNR-IVALSA, via Madonna del Piano, 10. Sesto Fiorentino (FI), Italy
2 Tropical Research Institute of Portugal (IICT), Forest and Forest Products Centre,
Tapada da Ajuda, Lisboa, Portugal
3 Soprintendenza per i Beni Archeologici della Toscana, Laboratorio di Analisi,
L.go del Boschetto, 3. Firenze, Italy
4 Department of Chemistry, BOKU-University of Natural, Resources and Applied Life Sciences,
Vienna, Austria
Abstract
The work concerns the characterisation of waterlogged archaeological wood samples from different
excavation sites in Italy by means of infrared spectroscopy. It describes some preliminary evaluations
of the analyses carried out, including a quantitative estimation of the holocellulose, one of the
structural chemical components constituting the cell walls.
1. Introduction
The structural modifications which wood undergoes during burial in waterlogged conditions [1-5]
imply the need for an effective treatment for a safe conservation after discovering. Till today such
treatments are in most of cases carried out without a complete diagnostic evaluation, except for a few
quick measurements of selected physical characteristics of the archaeological material [6]. This fact is
basically due to two series of reasons: the first one is imputable to the real usefulness of the diagnostic
analyses, actually not well connected to a practical use of the obtainable information; the second
reason is associated with the limited accuracy of the current methodologies and to the great effort
required in terms of time for their complete execution.
However, a phase of diagnostic evaluation preliminary to any kind of treatments is an essential step to
be accomplished because it allows for the possibility of checking, after consolidation, the presence of
eventual changes within the treated object, both in the short and the long term, when maintained either
in service conditions or during exposure at a museum. From this point of view, the well-known case of
Vasa is very representative [7]. Moreover, the evaluation of the extent of the decay allows for its
grading and therefore, potentially, for a treatment tailored to the specific state of preservation of a
finding. Within this framework, a quantitative, reliable and quick measurement of the structural
chemical components constituting the residual cell walls of the fossil material represents an important
step toward the broad applicability of a systematic approach intended to evaluate the state of
preservation of archaeological wooden finds at the time of their discovering. Among other techniques,
those related to infrared analysis seem to be the most promising, due to the fastness of execution, the
limited amount of sample required and to the relatively long experience in their application [8].
However, considering the high variability (mainly in terms of chemical structure) of the decayed fossil
material [9, 10] and the presence of various other factors potentially disturbing the interpretation of
analyses, like for example the ever considerable content of inorganic components, a research effort is
required before proposing this technique as a routinely protocol for diagnostic evaluations in the
archaeological field.
Aim of this work is describing a series of preliminary evaluations, performed on samples coming from
different sites of excavation in Italy, finalised to carry out a quantitative estimation of the chemical
structural components constituting the cell walls of archaeological wood, by mean of Attenuated Total
Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR).
* E-mail: macchioni@ivalsa.cnr.it
Joseph Gril (edited by), Wood Science for Conservation of Cultural Heritage –Braga 2008: Proceedings of the International
Conference held by COST Action IE0601 (Braga - Portugal, 5-7 November 2008, ISBN 978-88-6453-157-1 (print)
ISBN 978-88-6453-165-6 (online) © 2010 Firenze University Press