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This paper proposed phytoliths as promising for identifying and distinguishing sources of fibre in Chinese handmade papers. For an initial methodological exploration, two types of Raw Xuan (unprocessed Xuan paper) and the two plant materials used in making them—namely rice straw and bark from blue sandalwood (Pteroceltis tatarinowii Maxim.)—were collected. The dry ashing method was used to extract phytoliths from Raw Xuan and its plant materials. The results can be summarized as follows. First, phytoliths characteristic of rice (Oryza sativa) were abundant in both rice straw and Raw Xuan. By looking for rice phytoliths, it is possible to tell whether or not rice straw fibre is used in a particular paper. Second, hair cell phytoliths were observed in considerable quantities in blue sandalwood bark, but absent in the examined papers. Heat experiments showed that phytoliths in blue sandalwood were resistant to long-term heat and they would unlikely be eliminated when exposed to the heat in papermaking (with heat source barely above 200°C). It is hypothesised that they dissolved while cooked in an alkaline pH (limewater). Further studies are necessary to understand whether phytoliths in blue sandalwood—while cooked in limewater—undergo morphological changes and, if yes, how.

The crystallinity indices (CrI) of Chinese handmade papers were investigated using the X-ray diffraction (XRD) method. Four Chinese handmade papers, Yingchun, Zhuma, Yuanshu and Longxucao papers were used as model substrates of mulberry bark, ramie, bamboo and Eulaliopsis binata papers, respectively. Two forms of the paper samples, paper sheets and their comminuted powders, were used in this study. The results showed that their XRD patterns belong to the cellulose-I type and Iβ dominates the cellulose microstructure of these paper samples. Moreover, it was found that the microstructures and CrIs of cellulose of these papers were changed by the grinding treatment. This work suggested that the sheet form of the handmade papers is suitable to determine CrI by XRD, despite the contribution of non-cellulosic components in the papers. The order of CrIs for these paper sheet samples was Yingchun, Zhuma, Longxucao and Yuanshu papers. Besides CrIs, differences in cross-sectional areas of the crystalline zone of cellulose can be used for comparing different types of handmade papers. It was also found that the CrIs and crystallite size of paper cellulose varied between the sheet samples and the powder samples, illustrating that the pulverisation has a negative influence on the microstructure of the handmade papers. [ABSTRACT FROM AUTHOR]

This paper proposed phytoliths as promising for identifying and distinguishing sources of fibre in Chinese handmade papers. For an initial methodological exploration, two types of Raw Xuan (unprocessed Xuan paper) and the two plant materials used in making them—namely rice straw and bark from blue sandalwood (Pteroceltis tatarinowii Maxim.)—were collected. The dry ashing method was used to extract phytoliths from Raw Xuan and its plant materials. The results can be summarized as follows. First, phytoliths characteristic of rice (Oryza sativa) were abundant in both rice straw and Raw Xuan. By looking for rice phytoliths, it is possible to tell whether or not rice straw fibre is used in a particular paper. Second, hair cell phytoliths were observed in considerable quantities in blue sandalwood bark, but absent in the examined papers. Heat experiments showed that phytoliths in blue sandalwood were resistant to long-term heat and they would unlikely be eliminated when exposed to the heat in papermaking (with heat source barely above 200°C). It is hypothesised that they dissolved while cooked in an alkaline pH (limewater). Further studies are necessary to understand whether phytoliths in blue sandalwood—while cooked in limewater—undergo morphological changes and, if yes, how. [ABSTRACT FROM AUTHOR]

Handmade mulberry paper is a traditional bark paper of China dating back nearly two millennia and is still a popular medium used today for preserving and restoring Asian paper artefacts. In the present study, samples of modern Chinese mulberry paper from different traditional manufacturers were artificially aged by exposure to UVA radiation. Their degradation patterns and associated generation of superoxide anions and hydrogen peroxides were determined by means of various spectroscopic techniques following our previous approach. Furthermore, electron spin resonance (ESR) spectroscopy using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin-trapping agent was employed to detect hydroxyl radicals in irradiated paper as well as to provide additional information for the photodegradation mechanism. Like Xuan paper, Chinese handmade mulberry paper exhibited blue fluorescence (λex = 340 − 400 nm; λem = 450 − 480 nm) consistent with it originating from a number of naturally-occurring hydroxylcoumarins. UVA irradiation of papers of different origins resulted in varying changes to the fluorescent species, which, together with the hydrolysis or formation of chromophores absorbing in the visible region, leads to the photobleaching or photoyellowing of paper. The extent of photodiscolouration of different papers correlate with their relative rates of the production of reactive oxygen species (ROS), including hydrogen peroxides, superoxide anions and hydroxyl radicals. SEM-EDS analyses revealed that the Chinese mulberry paper studied in the work had high levels of calcium and phosphorous, together with a much lesser amount of potassium, iron and copper, which probably originate from details in their manufacturing methods. Papers containing high concentrations of these metal ions also exhibited higher yields of ROS, which contribute to a higher level of oxidative stress and thereby affects their photostability. The main mechanism for the photodegradation of Chinese mulberry paper is proposed to be a sensitised oxidation via the formation of activated ROS, catalysed by the presence of transition metal ions, particularly ferric and cupric, and was accelerated by other factors such as moisture. This study has provided detailed knowledge for the photodegradation process of Chinese mulberry paper, which aims to assist the development of effective treatments for the restoration of important paper cultural heritage objects. [ABSTRACT FROM AUTHOR]

Abstract: Papermaking has a special place in the cultural heritage of China. Papers made from different types of plant fibers were, and are still used for particular applications. Bamboo paper is a handmade paper that has been traditionally used for book printing and restoration of ancient paper objects since antiquity in China, whereas Xuan paper, the subject of recent previous study, is used for traditional Chinese calligraphy and painting. Following our previous approach on Xuan paper, four modern Bamboo papers manufactured using traditional or chemically-facilitated techniques were artificially aged by UVA radiation and changes to their optical properties were evaluated by reflectance and 3D-fluorescence spectroscopies. Paper samples produced by different methods displayed different fluorescence spectra and UVA photolysis of paper resulted in decreases in the fluorescence intensities and reflectance values, manifested as differing photoyellowing of the papers. Assays of reactive oxygen species, ROS, revealed that papers made by chemically-assisted pulping methods generally produce more hydrogen peroxide or superoxide radicals than those made by traditional methods, which correlates with their relative yellowing rates. Different spatial distributions of calcium and chlorine were also observed by SEM/EDS analysis in the chemically-manufactured papers, probably arising from the specific pulping and/or bleaching chemicals used in their manufacture. [Copyright &y& Elsevier]

Abstract: Xuan paper is a type of Chinese handmade paper produced for traditional calligraphy and painting in China since the Tang Dynasty (618–907AD), and is therefore an important cultural heritage material. In this study, the fluorescence and photochemical properties of Xuan paper were investigated. Xuan paper exhibits auto-fluorescence in the blue spectral range (450–500nm) and UVA photolysis of the paper resulted in a substantial reduction in the blue fluorescence together with the formation of chromophores absorbing in the visible spectrum, resulting in photoyellowing of the paper. A more significant yellowing of paper was observed when irradiated in the dry state than under wet conditions. The associated photogeneration of hydrogen peroxide and superoxide from three types of Xuan paper samples during irradiation showed a correlation between the yields of reactive oxygen species and their relative yellowing rates. The results are interpreted in terms of sensitised photooxidation via a mechanism of electron transfer involving the fluorophores in their excited singlet states being responsible for the photodegradation of Xuan paper. SEM/EDS analyses were performed on the Xuan paper samples to investigate their morphological and elemental characteristics. Silica-containing fibres characteristic of a special rice straw that grows in siliceous soil were observed in all types of Xuan paper. Micron-sized calcium precipitates possibly formed from the “lime-steaming” manufacture process were shown to protect against the acidification of paper during accelerated thermal ageing. [Copyright &y& Elsevier]