# NMR Relaxometry and IR Thermography to Study Ancient Cotton Paper Bookbinding
## 3 Results and Discussion
### 2d \({}^{1}\)H-NMR-R Measurements and Processing
This further supports the idea that the amorphous domains work as a reservoir of water in paper, mainly related to the exchange of water with the environment. The different hydration results with respect to relative humidity are shown in Figure 4a, where the one-dimensional T\({}_{2}\)-distributions are reported. They have been extracted from the T\({}_{1}\)-T\({}_{2}\) maps for the L\({}_{8}\)-section performed at 45% (open circles) and 100% RH (closed circles). We calculated the ordinate analyzing the integral of a cumulative part of the curve, comparable to the percentage of water volume. Therefore, equal areas correspond to the same fractions of the whole signal. The hydration behavior on RH and on L\({}_{n}\)-section is further evidenced by estimating the trend of the moisture content (MC). As the inspected areas are larger than the sensitive volume of the surface probe, the NMR signal amplitudes acquired on the L\({}_{n}\)-sections allow assessing the moisture content's spatial distribution of the cover. By integrating the signal density distribution over the full range of T\({}_{1}\) and selected ranges of T\({}_{2}\) (computed by deconvolution of each T\({}_{2}\)-distribution), MC\({}_{\rm low}\) and MC\({}_{\rm high}\), pertaining the low- and high-T\({}_{2}\) water populations, respectively, were evaluated and reported in Table 1.  
Figure 4: \({}^{1}\)H-NMR T\({}_{2}\)-distributions of **(a)** L\({}_{8}\)-section acquired at 45% (open circles) and 100% (closed circles) RH, **(b)** L\({}_{6}\)-section (open circles) and L\({}_{5}\)-section (closed circles) acquired at 100% RH. The corresponding integrals over T\({}_{2}\) are also reported. Figure 3: 2D \({}^{1}\)H-NMR T\({}_{1}\)–T\({}_{2}\) maps of L\({}_{3}\)-, L\({}_{4}\)-, L\({}_{6}\)-, L\({}_{7}\)-, L\({}_{8}\)-, L\({}_{9}\)-, L\({}_{11}\)- and L\({}_{12}\)-sections acquired at 100% RH. The graphic layout of the maps is the same as in Figure 2.  
From the above results, we can observe that, when the relative humidity goes up, the low-T\({}_{2}\) population increases less than 10%, while the high-T\({}_{2}\) population gains over 120%. These data confirm that, by raising the RH percentage, the excess of water molecules quite exclusively enhances the liquid-like water component. In Table 1, we also reported % MC\({}_{\text{high}}\), that is the amount of the high-T\({}_{2}\) population with respect to the total volume fraction occupied by water in the sensitive volume of the NMR probe. It is equal to 20% at 45% RH, and 33% at 100% RH and these values are nearly constant for all the L\({}_{\text{n}}\)-sections. Notwithstanding, for both RH datasets, a comparison between the different areas of the front cover underlines L\({}_{1}\)- and L\({}_{5}\)- section's hydration capacity, 15% and 25% higher than the corresponding mean values computed on all the L\({}_{\text{n}}\)-sections (last row of Table 1). As shown in Figure 4b, for L\({}_{6}\)- and L\({}_{5}\)-section obtained at 100% RH this behavior seems to be a common feature for both water phases in the amorphous cellulose network. More precisely, the low-T\({}_{2}\) population, due to dynamically high confined water molecules fast exchanging with OH groups of the cellulose chains, and the high-T\({}_{2}\) population linked to few and more mobile water molecules in porous amorphous cellulose fractions. As water molecules exclusively occupy amorphous domains, the larger amount of signal in L\({}_{1}\) and L\({}_{5}\) may be the effect of an increase of the accessible sites for both water components within the cellulose network. This could be ascribable to biochemical events that led to the cleavage of hydrogen bonds between cellulose chains of the amorphous regions [12] or to a modification of the crystalline-amorphous interfaces with an increase of the amorphous phase to the detriment of the crystalline one.