Atsuko Ishikawa

In situ measurement of wood moisture content in high-temperature steam

Changes in moisture content of sugi (Cryptomeria japonica D. Don) wood during high-temperature saturated and superheated steam treatments were investigated. A system for in situ weighing of specimens was used, and the reduction of wood substance by heating was taken into consideration. At 160°C the loss of wood substance due to heating was significant and influenced the moisture content values, but it was almost negligible at 120°C. Treatment time and temperature affected the moisture content in saturated steam but not in superheated steam. Excess water in a saturated closed system appears to promote the decomposition of wood and condensation in or on specimens.

Simple separation of Torreya nucifera and Chamaecyparis obtusa wood using portable visible and near-infrared spectrophotometry: differences in light-conducting properties

The identification of wood species in artifacts of archeological/historical significance is important both for repairing and maintaining the artifacts and for understanding their historical and cultural backgrounds. For nearly 20 years, we have examined wood in artifacts by collecting minute, naturally detached fragments and observing them with light or scanning electron microscopy [1–3]. We found that the woods of Torreya sp. (Taxaceae) and Chamaecyparis sp. (Cupressaceae) were frequently used to construct Buddhist statues after the 8th century AD. One problem with the above approach is that it is sometimes difficult to obtain samples with sufficient quality and quantity to make a definitive identification. For this reason, it is important to develop alternative methods for a non-invasive examination of artifacts. We have applied near infrared (NIR) spectroscopy to noninvasively identify wood species frequently used in wooden Buddhist statues. In doing so, we achieved a successful separation of T. nucifera and C. obtusa using multivariate analysis [4, 5]. However, it is considered that the separation of both species becomes difficult in the case of wooden Buddhist statues made more than several 100 years ago, because of the degradation of chemical compositions caused by exposure to circumferential condition for a long time. Then, other methods for separating both species without referring to the chemical compositions are desired. In this study, we developed a simple method to separate T. nucifera and C. obtusa based on the difference in the light conductivities of their wood. We then evaluated the possibility of separating T. nucifera and C. obtusa using a portable photospectrometer.

Depth profiling of photodegraded wood surfaces by confocal Raman microscopy

Weathering leads to rapid depolymerization of the chemical components and degradation of the cellular structure of wood [1, 2]. These changes are facilitated by a combination of solar radiation, moisture, temperature, air pollutions, and other factors. Among them, solar radiation is most damaging to wood because ultraviolet (UV) rays cause free radical oxidation and the reactions that significantly deteriorate the constituents of wood [1, 3]. Light-induced degradation, also called photodegradation, of wood occurs in its surface layer. An earlier study that employed electron spin resonance (ESR) estimated that UV and visible light penetrate wood to a depth of 75 and 200 μm, respectively [4]. Later works by Kataoka et al. reported that, on the basis of Fourier transform infrared (FTIR) microscopy measurements, that the depth of light penetration into wood and the spreading rate of the degradation layer depend on the wavelength of light source [5], exposure time [6, 7], and wood density [8]. In addition, several other tools have also been employed to investigate the depth analysis of photodegraded wood [9–12]. Recently, high spatial resolution IR microscopy techniques such as infrared scanning near-field optical microscopy (IR-SNOM) and atomic force microscopy-based infrared spectroscopy (AFM-IR) have been developed, but there are only a few applications of these techniques to wood samples [13, 14]. Confocal Raman microscopy is useful for evaluating the molecular structure of various materials with a high spatial resolution [15]. In recent years, this technique has come to be used in topochemical studies of native [16, 17] and modified wood [18, 19]. Although some Raman methods such as FT-Raman [20] and UV resonance Raman spectroscopy [21] have been applied for monitoring of wood photodegradation, micro-scale investigation using the confocal system has not yet been performed. Therefore, in the present work, confocal Raman microscopy, which is helpful in investigating the micro-distribution of functional groups in wood cell walls, has been applied to the depth profiling analysis of lightexposed wood surfaces.

Combustibility of fire-retardant impregnated and surface-coated wood after 5 years of natural weathering

The weatherability and combustibility of fire-retardant-impregnated wood during natural weathering for up to 60 months were evaluated. Fire-retardant chemicals used were modified guanidine phosphate with phenolic additives in order to retain chemicals against leaching. The ability of coating was also examined using four solvent-born coating systems:1 penetrating;semi-transparent(brown), 2 thin-film-forming;semi-transparent(brown), 3 film-forming;opaque(white), 4 film-forming;transparent. The systems 1 and 2 consisted of 2 or 3-coat application of each single coating composition, whereas 3 and 4 employed specific wood-sealers as an undercoat to stabilize the surface of wood prior to the application of topcoat. Phenolic additives were effective to maintain chemical retention for a certain period. After 60-month-natural weathering, coated specimens and uncoated specimen were at a quasi-non-combustible material level and a fire-retardant material level, respectively. Fire performance of specimens coated with 3 and 4 were better than 1 and 2.

Correction to: Acetaldehyde emission from wood induced by the addition of ethanol

The article Acetaldehyde emission from wood induced by the addition of ethanol, written by Shin-ichiro Tohmura, Atsuko Ishikawa, Kohta Miyamoto and Akio Inoue, was originally published Online First without open access.