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Diagnostic methods and historical document and artwork (in particular, paper items) analysis using modern physical methods is a topical practical problem.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.

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Confocal Raman microspectroscopy is used to substantially supplement existing experimental data on historical blue‐green beads with respect to the presence and distribution of potassium antimony silicate (KSS) crystals. Problem of degradation of blue‐green beads on historical artifacts accounts for topicality of the work. The reasons for possible short‐term (several years) degradation of beads and the presence of neighboring damaged and undamaged beads on a single item remain unknown in spite of multiple experimental works on various glasses. Presence of KSS microcrystals may serve as a reason for degradation of beads. Raman measurements at several depths are used to determine the distribution and estimate sizes of KSS microcrystals. Such distributions are different for undamaged and strongly degraded beads. For degraded beads, Raman data show the depth dependence of the concentration of (non)bridged oxygens in the near‐surface layer with a thickness of 3–4 μm (i.e., inhomogeneity of glass matrix). The results prove the growth of KSS microcrystals in historical blue‐green beads, which may cause internal stress and, hence, degradation. The results can be used for optimization of storage conditions and restoration procedures for historical items.

The goal of this work is to investigate the porosity of old paper with foxings. Initially, paper samples are characterized using the conventional absorption and Fourier transform infrared spectroscopies. Optoacoustic method based on laser excitation of short ultrasound transients is used for porosity measurements. The paper porosity is calculated using the theory of two-component mixture with the experimentally determined sound speeds in paper samples saturated with liquids. An increase in the porosity in foxing stains on paper in comparison with the foxing-free fragments is clearly demonstrated.