Raman Microspectroscopy of Old Paper Samples with Foxing

Abstract

Diagnostic methods and historical document and artwork (in particular, paper items) analysis using modern physical methods is a topical practical problem. Paper materials exhibit nonuniform degradation with the formation of foxing stains. Correct physicochemical identification of the structure of foxed fragments depends on the efficiency of the experimental technique and offers guidelines for restoration. Raman spectroscopy makes it possible to characterize old paper samples; however, to our knowledge, a comprehensive Raman analysis of foxing has not been done. In this study, we demonstrate that Raman microspectroscopy allows the identification of spectral changes related to paper aging and foxing formation. The degree of degradation of the rag papers studied here is noticeably less than the degree of degradation of the wood-cellulose papers. The spectral differences among 19(th)-, 20(th)-, and 21(st)-century papers are revealed. The presence of lignin and gypsum filler in the 20th-century paper is demonstrated. Raman data indicate that the foxed fragments exhibit a stronger degradation of the paper. The spectral differences between the foxed and unfoxed fragments are discussed. The results can be used in the restoration of paper documents and artworks, in particular for identification of foxed fragments.

Ageing of ancient paper: A kinetic model of cellulose degradation from Raman spectra

“…Notwithstanding some rare exceptions, the observation of lignin indicates that the cellulose was obtained from wood pulp, a common commercial choice in paper production since the XIX century. Lignin is mainly responsible for the degradation processes in modern paper because of its photo‐oxidation properties, leading to the production of a low‐cost low‐quality paper in the last centuries. To confirm the previous indications, ancient samples did not show the presence of lignin whilst, as expected, it is observed in modern paper.…”

“…The worst conservation status was recorded for the C2E sample, whose printing date claims for less than 100 years of ageing whilst the estimated effective date is more than 300 years for the whitest point and more than 400 years for the darkest one. This is not surprising, because the C2E sample is the only one containing lignin, which accelerates the degradation process . One could hypothesize that if data were available, a different reference curve could be calculated by considering different values of mean temperature and/or relative humidity, whose contribution is accounted for by the k factor in Equation .…”

“…Notwithstanding some rare exceptions, the observation of lignin indicates that the cellulose was obtained from wood pulp, a common commercial choice in paper production since the XIX century. Lignin is mainly responsible for the degradation processes in modern paper because of its photooxidation properties, [17,23] leading to the production of a C1A Carta De Logu Known as "Code of Eleonora di Arborea," represents the first collection of laws, written in Sardinian language, entirely dedicated to the Sardinian Giudicati (medieval regional states ruled by judges) 1400-1500 [33,34] C1B Condaghe di San Martino Paper manuscript, considered as an administrative book belonging to the convent of San Martino of Oristano 1462 [35,36] C1C Nova Scientia Written by the mathematician Niccolo' Tartaglia (Nicolo Tartalea), is a printed book with figures 1537 [33] C1D Il vago et dilettevole Giardino (Private Collection) written by Luigi Contarino Crucifero, represents a collection about epic poems on sibyls and muses, discussion on human virtues and ethical tales on some prophets 1597 [37] C1E Institutiones Philosophicae (Private Collection) is an advanced handbook of physics written by Kasper Sagner 1758 [38] C1F Traité élémentaire de physique (Private Collection) written by Antoine Libes, (1752-1832). This text, reprinted several times, was widely adopted as a vade-mecum of physics during the XIX century 1803 [39] C0 Modern Paper-Fabriano, 2017 Reference paper representative of the contemporary age.…”

“…Indeed, ageing and conservation conditions are strongly correlated, and the estimated age of a certain relic (or part of it), that is, the effective age as compared with the printing date, can tell a lot about the use and the conservation state of the relic. In this work, attention was concentrated on the cellulose structure, aiming to investigate the degradation process of cellulose paper, a process associated with the breaking of the glucose chain units . The idea was to exploit Raman spectroscopy to date cellulose library documents and to correlate some Raman bands intensities to ageing conditions.…”

“…In this work, attention was concentrated on the cellulose structure, aiming to investigate the degradation process of cellulose paper, a process associated with the breaking of the glucose chain units. [22][23][24][25][26][27][28][29] The idea was to exploit Raman spectroscopy to date cellulose library documents and to correlate some Raman bands intensities to ageing conditions. Library public and private heritage across seven centuries (XV-XXI) were analysed, supporting the analysis with literature data (concerning the assignation of Raman bands) and density functional theory (DFT) molecular chemistry simulations.…”