We successfully transferred and applied -omics concepts to the study of material degradation, in particular historic paper. The main volatile degradation products of paper, constituting the particular "smell of old books", were determined using headspace analysis after a 24 h predegradation procedure. Using supervised and unsupervised methods of multivariate data analysis, we were able to quantitatively correlate volatile degradation products with properties important for the preservation of historic paper: rosin, lignin and carbonyl group content, degree of polymerization of cellulose, and paper acidity. On the basis of volatile degradic footprinting, we identified degradation markers for rosin and lignin in paper and investigated their effect on degradation. Apart from the known volatile paper degradation products acetic acid and furfural, we also put forward a number of other compounds of potential interest, most notably lipid peroxidation products. The nondestructive approach can be used for rapid identification of degraded historic objects on the basis of the volatile degradation products emitted by degrading paper.

Until recently, applications of spectral imaging in heritage science mostly focused on qualitative examination of artworks. This is partly due to the complexity of artworks and partly due to the lack of appropriate standard materials. With the recent advance of NIR imaging spectrometers, the interval 1000-2500 nm became available for exploration, enabling us to extract quantitative chemical information from artworks. In this contribution, the development of 2D NIR quantitative chemical maps of heritage objects is discussed along with presentation of the first quantitative image. Further case studies include semiquantitative mapping of plasticiser distribution in a plastic object and identification of historic plastic materials. In the NIR imaging studies discussed, sets of 256 spatially registered images were collected at different wavelengths in the NIR region of 1000-2500 nm. The data was analyzed as a spectral cube, both as a stack of wavelength-resolved images and as a series of spectra, one per each sample pixel, using multivariate analysis. This approach is only possible using well-characterized reference sample collections, as quantitative imaging applications need to be developed, thus enabling spatial maps of damaged and degraded areas to be visualized to a level of chemical detail previously not possible. Such quantitative chemical mapping of vulnerable areas of heritage objects is invaluable, as it enables damage to historic objects to be quantitatively visualized.

Iron gall inks are of extraordinary historical significance considering their widespread use for over a millennium. Due to their corrosiveness, which is a consequence of their acidity and content of transition metals, iron gall inks accelerate the degradation of the writing or drawing support, which in this study is rag paper. Characterisation of acidity (pH) and degree of polymerisation (DP) of cellulose in paper is thus of high interest as it enables the estimation of material stability and assessment of risks associated with its handling. Based on a well-characterised set of samples with iron gall ink from the 18th and 19th centuries, we developed a near infrared spectroscopic method with partial least squares calibration for non-destructive determination of pH and DP of both inked areas and paper. Using this method, 27 18th and 19th century iron gall ink drawings from the British Museum collection were analysed and in all cases, inked areas turned out to be more acidic and degraded than the surrounding paper. Based on the obtained DP data, we were able to estimate the time needed for the inked areas to degrade to the point when they become at risk of damage due to handling. Using the average uncertainty of the calculated lifetime, we propose a quantitative stability classification method which could contribute to the curatorial and conservation decision-making process.

Quantitative non-destructive analysis of individual constituents of historic rag paper is crucial for its effective preservation. In this work, we examine the potentials of mid-and near-infrared spectroscopy, however, in order to fully utilise the selectivity inherent to spectroscopic multivariate measurements, genetic algorithms were used to select spectral data derived from information-rich FT-IR or UV-VIS-NIR measurements to build multivariate calibration models based on partial least squares regression, relating spectra to gelatine content in paper. A selective but laborious chromatographic method for the quantification of hydroxyproline (HYP) has been developed to provide the reference data on gelatine content. We used 9-fluorenylmethyl chloroformate (FMOC) to derivatise HYP, which was subsequently determined using reverse-phase liquid chromatographic separation and fluorimetric detection. In this process, the sample is consumed, which is why the method can only be used as a reference method.The sampling flexibility afforded by small-size field-portable spectroscopic instrumentation combined

INTRODUCTIONIron gall inks were the most commonly used writing and very popular drawing media since antiquity. It is well known that these kinds of inks were produced by mixing aqueous solutions of iron(II) sulphate with extracts of gall nuts. 1 Iron gall inks are known to infl uence the structure of cellulose fi bres in a specifi c way, causing the deterioration of paper. The complex chemical processes between the ink and the paper support depend on several factors, ranging from the materials composition to environmental infl uences as has been mapped in a simplifi ed scheme. 2 The overall process of paper degradation may be seen as a combination of several mechanisms. Among them, the 1) acid-catalysed hydrolysis causing a reduction of the mechanical paper properties via shortening the cellulose polymeric chains, and 2) metal-catalysed oxidation of materials with subsequent development of volatile compounds, mechanical weakening and discolouration, are most frequently described. 3 These two processes can often occur simultaneously, but under certain conditions can proceed independently even when the other process is absent. 1,2,3,4,5 This present study has two aims. It characterises the cellulose artifi cially aged by a combination of heat and humidity in the presence of Fe(II), Fe(III) and model inks. Additionally, the methods and techniques were investigated in terms of their suitability for the analysis of degraded cellulose, as it concerns the description of the chemical and physical changes effected by the ageing procedure. In order to evaluate the deterioration of paper, the samples were analysed destructively by the conventional methods i.e. pH measurements, viscosity or bursting strength and additionally by non-destructive FTIR and colorimetric methods.