Proceedings e report - Firenze University Press

WOOD SCIENCE FOR CONSERVATION OF CULTURAL HERITAGE
Fig. 2. Spectra of sample B01, from the site of Naples, subjected to several treatments in order to evidence the
changes in its spectrum due to the presence of ashes. The spectrum of the water extract is also shown.
3.2. Calibration
Calibration is the most important step in the quantitative evaluation of the structural components of
wood by means of the ATR-FTIR spectra. In the case of samples having low amount of inorganic
components it can potentially give good results, mainly if samples belonging to the same wood species
are considered (Fig. 3). The example of elm samples coming from the sites of Pisa and Comacchio
shows that only cm_C1, with an ash content almost tripling (Table 1) the amount of the other samples
is an outlier, whereas pp_B2 and pp_B29, showing an ash content higher than others but however of
the order of 5%, are acceptably aligned along the calibration straightline (Fig. 4). In the same way
other samples belonging to other species than elm and having ash content higher than 10% are also not
aligned with the identified calibration (Fig. 4), even if a parallel straightline could probably be drawn
(not reported in the figure).
Fig. 3. Min-Max (1800-1507 cm -1 ) normalized spectra of seven extracted elm samples from Comacchio
(cm_C01 to cm_C07), two from Pisa (pp_B2 and B29) and the extracted fresh elm spectrum (blue).
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