Newly Introduced/Updated Instruments at the Center for Conservation Science in FY2024

　In FY2024, the Conservation Science Center newly installed a Raman spectrometer, a 3D fluorescence spectrophotometer, and a high-performance liquid chromatography system, and updated the existing pyrolysis GC/MS and ion chromatograph. These instruments are introduced below. (Figure 1)

Raman spectrometer
　When a material is irradiated with laser light, the wavelength of Raman scattered light changes depending on the molecular structure of the material at the point of irradiation. Using this principle, it is possible to analyze the structure of a sample in a non-contact and non-destructive manner. For this purpose, we have introduced three types of instruments: a stationary Raman microspectroscope that can also be used for mapping, a portable Raman microspectroscope that can be carried around, and a hand-held Raman spectroscope that is compact and easy to carry around. Raman spectroscopy can be used to analyze any sample other than pure metals, whether inorganic or organic. It can be used for various applications such as identification of dyes and pigments, elucidation of the causes of corrosion, and analysis of adhering materials on cultural properties. (Figure 2)

Three-dimensional spectrofluorometer
　Since the wavelength and intensity of fluorescence emitted from a sample varies depending on its structure, fluorescence analysis can be used to estimate the structure of materials constituting cultural properties. It is a non-contact, non-destructive measurement method and can be used to analyze any sample that emits fluorescence. There are a surprisingly large number of samples that emit fluorescence (for example, fluorescence can be detected in cloth, paper, and wood in many cases), and many cultural properties can be analyzed using this method, but it is a particularly powerful analysis tool for dyes. (Figure 3)

High-performance liquid chromatography system
　Used for the determination of aldehydes in the air and dyes in textiles, this system is equipped with a PDA detector, which is more powerful than a typical UV detector for identifying unknown substances. Since extraction is required, this is basically a destructive analysis method.

Pyrolysis GC/MS (updated)
　This instrument is capable of analyzing in detail the structure of samples consisting of polymers, such as paper, fabric, lacquer, and wood. Although it is a destructive method, it is possible to analyze even a very small amount of sample (1 mg). Qualitative quantification of atmospheric odors and residual solvents is also possible.

Ion chromatograph (updated)
　This is used for the quantitative determination of ammonia and organic acids in the air, and chloride and nitrate ions in water. It employs a suppressor method and is extremely sensitive.

　We will continue to analyze cultural properties using these instruments.

It can be seen that the spectra obtained are different depending on the material colorant. A resolution of 1 µm enables identification of the colorant material. In particular, the ability to analyze inksticks nondestructively is a major feature. In addition to pigments, a wide variety of samples can be analyzed, including dyes, minerals, metal corrosion, and fibers.

Accelerated aging test causes an overall decrease in fluorescence intensity. In particular, there are marked decreases in fluorescence intensity around the excitation wavelength of 280 nm and fluorescence wavelength of 420 nm. Since the fluorescence pattern changes depending on the degree of deterioration and the material itself, it is useful for evaluating the degree of deterioration and for analyzing the differences between different materials.

Newly introduced instruments at the Center for Conservation Science in FY2023

　In FY2023, the Center for Conservation Science introduced a microtome, a biological microscope (with polarized light, phase contrast, and differential interference observation functionality), and an infrared microscope (Fig. 1). The following is an introduction of these newly introduced instruments.

Microtome
　The microtome is a device used to precisely cut samples to facilitate observation. For example, when analyzing what kind of material a piece of paper or cloth is made of, a sample is sometimes cut and its cross section is observed under a microscope. Conventionally, samples are cut with razor-sharp blades or embedded in resin and polished. However, these methods can present problems such as deformation of the specimen and difficulty in observing the specimen because it is embedded in resin, and they require skillful manipulation. The microtome solves these problems and makes it easier to identify paper and cloth materials. Figure 2 shows an example of actual cross-sectional observation results. The microtome can be applied to all cultural assets made of organic materials such as wood and lacquerware.

Biological Microscope
　Polarized light observation, phase-contrast microscopy, and differential interference microscopy are effective for observing crystal structures, microstructures, and cells and biological tissues, respectively. For example, they are effective for observing mold and bacteria on cultural properties, fibers of paper and textiles, and starch glue and other glues used for cultural properties.

Infrared microscope
　Infrared cameras are often used to observe cultural properties. This type of microscope can be used to clearly see ink lines and certain types of dyes used in calligraphy and paintings, and to identify materials and observe the underlying surface of paintings.

　We will continue to analyze cultural properties using these devices.

Figure 1. Photographs of newly introduced instruments

Microtome

Biological microscope

Infrared microscope

Figure 2. Cross section of Najio Gampi paper

Cross-section produced using a scalpel

Cross-section produced using a microtome

　When a scalpel is used to produce a cross section, a large amount of clay minerals are pressed down by the blade, covering the gampi fibers and causing them to lose their original shape. When the cross section is produced with a microtome, the gaps between fibers can be confirmed, and the hollow structure of the fibers remains intact.

Study for a Stable Supply of Noriutsugi (2)

　In our December 2022 Monthly Report, we reported on the “neri,” a sort of “dispersant” used in papermaking, extracted from noriutsugi (Hydrangea paniculate). This report is a continuation of that previous report.
　Since last year, noriutsugi collected in Shibetsu-cho, Hokkaido Prefecture has been shipped to various papermaking areas and used as neri for papermaking, but problems such as blackening of the neri have been observed in some areas. Analysis of the causes of the blackening confirmed that it is caused by a combination of three conditions: heating during neri extraction, contamination of tannins in the outer bark, and the absence of preservatives. Therefore, the blackening can be eliminated by carefully removing the outer bark or by adding a small amount of preservative. This result was reported at the 45th annual meeting of The Japan Society for the Conservation of Cultural Property (National Museum of Ethnology, June 24-25), and the presentation was very fruitful, receiving many questions.
　In addition, we visited the production sites of Uda paper (Yoshin-cho, Yoshino-gun, Nara Prefecture) and Echizen washi (Echizen-shi, Fukui Prefecture), which are made using noriutsugi, in succession (March 6 for Uda and July 19 for Echizen) and conducted a survey of the paper-making process. In both of these production areas, the shortage of noriutsugi is a major problem, and the supply from Shibetsu-cho is expected to be of great help. It was also confirmed once again that there are different ways to use noriutsugi neri depending on the production area and the craftsman, and it is necessary to consider supply methods that meet the needs.　In addition, on July 27, we visited Shibetsu-cho to observe the collection of noriutsugi bark, to study the collection method and to record and photograph the process. This year, about 200 kg of noriutsugi bark has already been collected and shipped to various papermaking regions.
　We will continue our activities to ensure a stable supply of noriutsugi.

Uda-gami papermaking, using noritsugi from Shibetsu-cho

Noritsugi used for Echizen washi

Noriutsugi, which grows wild in large quantities in Shibetsu-cho

Collecting bark

Investigation for Sustainable and Stable Supply of Noriutsugi

Noriutsugi
Neri is extracted from noriutsugi bark. The yellow part of the tree is where bark has been removed.

Discussion meeting in TOBUNKEN

　Washi (Japanese traditional paper) is used for the restoration of cultural properties and for traditional crafts. It is well known that washi is made of fibers extracted from plants such as kōzo (Broussonetia kazinoki x B. papyrifera) and ganpi (Diplomorpha sikokiana). However, it is not widely known that neri, a dispersant, is also essential for washi making. Adding neri disperses the fibers evenly in water, producing smooth and beautiful washi. Without the addition of neri, the fibers are not evenly dispersed, and washi made without neri has poor formation.

　Including washi most cases of industrial mass paper manufacturing use synthetic compounds such as polyethylene oxide as neri. Traditionally, neri is made from mucilage extracted from plants such as tororoaoi (Abelmoschus Manihot) and noriutsugi (Hydrangea paniculate). At present, neri extracted from tororoaoi or noriutsugi is still most suitable for thin washi making. It is also widely used for washi-making for cultural property restoration. However, the sustainable and stable supply of these raw materials, especially noriutsugi, becomes increasingly difficult. This is because noriutsugi for neri is a wild species and there are not enough successors to the experts with knowledge on locating noriutsugi and removing its bark. If the low amounts of noriutsugi available does not change, this will permanently impair washi-making for the restoration of cultural property. For example, uda washi paper used for soura-kami (the final lining paper) of hanging scrolls is made using neri extracted from noriutsugi. Therefore, we are concerned that restoring hanging scrolls will become difficult in the near future.

　Commissioned by the Agency for Cultural Affairs, the Center for Conservation Science has been conducting a research project: “Investigation of Tools and Materials Used for the Preservation and Restoration of Fine Arts and Crafts” with the Department of Art Research, Archives and Information Systems and the Department of Intangible Cultural Heritage. As an important investigation of this project, we are working for sustainable and stable supply of noriutsugi. This investigation is conducted in cooperation with Hokkaido Prefecture, Shibetsu Town and others. We visit the noriutsugi growing area in Shibetsu Town and hold regular discussion meetings. We will provide supports for sustainable and stable supply of noriutsugi and conduct scientific studies on why neri extracted from noriutsugi shows such excellent characteristics.