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Paper (books, manuscripts and graphic art) has conveyed artistic expression and knowledge for several centuries. The need to preserve paper-based cultural objects housed in museums and archives is ever more urgent. In order to propose adequate preservation solutions, the physical and chemical long-term behaviour of paper was investigated. Different complementary approaches that allow for a close examination of considerations such as chemical stability and conservation of paper-based artefacts are presented. Outcomes of research conducted with the aim of better understanding the reactive phenomena that unfold during the natural and artificial ageing of paper are discussed, as well as the development of analytical methods for a precise and accurate appraisal of degradation processes and levels. The impact of the collections environment and the development of preservation strategies through novel preventive and remediation processes are uncovered., Les documents sur papier (livres, manuscrits et œuvres d’art) sont les véhicules privilégiés de l’expression artistique, et de l’acquisition et la dissémination de la connaissance. La nécessité de préserver le patrimoine sur papier, constitué à travers les siècles dans les collections muséales et archivistiques n’a jamais été aussi pressante. Afin de proposer des solutions de préservation il est important de mieux connaître le comportement physique et chimique du papier à long terme. Différentes approches complémentaires permettant un examen des problèmes majeurs afférents à la stabilité et à la conservation des documents graphiques du patrimoine culturel sont abordées. Nous évoquons les travaux menés sur la compréhension des phénomènes réactionnels se déroulant au cours du vieillissement naturel et artificiel du papier et le développement de méthodologies analytiques permettant d’apporter des informations précises et nouvelles sur les processus de dégradation et les niveaux d’endommagement. Les questions relatives à l’environnement des collections et au développement de stratégies de préservation par des procédés préventifs et curatifs nouveaux sont également présentées.

International audience; Better understanding the parameters influencing the durability of historic papers and lignocellulosic materials in general is a fundamental area of research in the field of preservation of historic paper-based artefacts. The state of degradation of cellulose determines the mechanical properties of paper, which ultimately is the criterion to be related to the useful lifespan of paper. The main cause of decay of paper is its acid content in combination with time and conditions of exposure, as upon ageing cellulose undergoes acid catalysed hydrolysis and oxidation reactions. The macromolecular characterisation of cellulose is thus a pivotal aspect in the research and sensitive analytical methods have to be developed to possibly enable diagnostics of the alteration levels with application to historic objects. In that respect, size-exclusion chromatography (SEC) is a technique of choice because it is very sensitive to evidence early degradation. Coupled on-line with multi-angle light scattering (MALS) detection, the information on the molar mass and the size distributions, as well as the polydispersity of a polymer is extremely precise as absolute values of the molar mass averages are determined. The unique advantage of MALS experiments in chromatography mode is that no calibration is required. SEC/MALS thus provides a fine and accurate characterisation of cellulose upon dissolution of paper in an appropriate solvent (lithium chloride/N,N-dimethylacetamide).Another aspect to be considered for the comprehensive study of the deterioration of cellulosic cultural heritage relates to the by-products and fragments from paper degradation. A large part of the molecules formed have low-molar mass, and depending on which polymer they originate from in the paper (cellulose, hemicelluloses, lignin), they are aliphatic and aromatic compounds with carbonyl, and carboxyl functionalities, and carbohydrates. Due to sampling constraints, a primary aim in the field of cultural heritage preservation science is to establish useful micro-destructive, and whenever possible non-invasive, methodologies. As material sampling is often unavoidable, these techniques should evolve towards sample miniaturisation. Capillary electrophoresis (CE) is well adapted to minute amounts of sample. The performance of this technique in terms of selectivity, efficiency and resolving power is even enhanced when coupled to high sensitivity detectors such as mass spectrometers (MS), which provide molar mass (m/z) and some structural information. CE/ESI-MS (electrospray ion source) in particular is especially adapted for the analysis of complex samples.