Wavelength Dependence of Light Induced Changes in Reflectance Spectra of Selected Dyes and Pigments

Historical objects in exhibitions can be subject to light induced damages resulting in a shift of color and brightness. Besides certain ambient influences the main factor governing these effects is the spectral irradiance applied to the surface. As the photochemical efficiency of electromagnetic radiation depends on its wavelength it is desirable to know the effect of individual spectral components in order to estimate the damage potential of a certain light source. In this work the modifications of the reflectance spectra of 40 dyes and pigments relevant in historical book illumination resulting from irradiation by eight narrow band LED light sources are presented. The LED wavelengths cover the visible part of the electromagnetic spectrum. Based on the measured reflectance spectra, color values are calculated and their evolution is studied as a function of the amount of radiation applied.     

Photochemical colour change for traditional watercolour pigments in low oxygen levels

Abstract

An investigation for light exposure on pigments in low-oxygen environments (in the range 0–5% oxygen) was conducted using a purpose-built automated microfadometer for a large sample set including multiple samples of traditional watercolour pigments from nineteenth-century and twentieth-century sources, selected for concerns over their stability in anoxia. The pigments were prepared for usage in watercolour painting: ground and mixed in gum Arabic and applied to historically accurate gelatine glue-sized cotton and linen-based papers. Anoxia benefited many colorants and no colorant fared worse in anoxia than in air, with the exception of Prussian blue and Prussian green (which contains Prussian blue). A Prussian blue sampled from the studio materials of J.M.W. Turner (1775 ? 1851) was microfaded in different environments (normal air (20.9% oxygen) 0, 1, 2, 3.5, or 5% oxygen in nitrogen) and the subsequent dark behaviour was measured. The behaviour of the sample (in normal air, anoxia, and 5% oxygen in nitrogen) proved to be consistent with the 55 separately sourced Prussian blue samples. When exposed to light in 5% oxygen in nitrogen, Prussian blue demonstrated the same light stability as in air (at approximately 21°C and 1 atmosphere). Storage in 5% oxygen is proposed for ‘anoxic’ display of paper-based artworks that might contain Prussian blue, to protect this material while reducing light-induced damage to other components of a watercolour, including organic colorants and the paper support.     

Exposure of artists' colorants to airborne formaldehyde

Abstract

Thirty artists' colors have been exposed for 12weeks to 120ppb of formaldehyde in purified air as well as to purified air alone (control experiment). The exposure was carried out in the dark at ambient temperature (19 ± 2°C) and humidity (RH 44–52%). Color change (?E) was measured using a reflectance color analyzer after one, two, three, four, six, eight, 11 and 12 weeks of exposure. Color parameters (x, y, X, Y, Z, L*, a*, b* and ?E)"were also calculated from the 380–700nm spectra, recorded with a reflectance spectrophotometer, of unexposed colorants and of colorants exposed for 12 weeks to purified air and to formaldehyde. Regression analysis of the two data sets indicated that the color changes measured by these two methods were in excellent agreement (nearunity slopes, with correlation coefficients > 0.99). Exposure to either formaldehyde or pure air on watercolor paper resulted in little or no color change for all the colorants tested, including inorganic colorants, alizarin lakes, quinacridones, triphenyl methanes, indigo derivatives, arylamides and natural colorants such as curcumin. Formaldehyde, which is ubiquitous in indoor air, including museum air, does not appear to be a major threat to colorants in museum collections.     

Can LEDs help with art conservation? – Impact of different light spectra on paint pigment degradation

The impact of the spectral composition of light on the discoloration of paint pigments has been investigated for the case of lead chromate sulfate, an unstable yellow pigment used by Vincent van Gogh and other painters. With LEDification, museum lighting is moving from using halogen to LED lamps. LED light sources have a significantly different spectral composition than halogen lamps. To understand the impact of these differences on pigment stability, the wavelength dependence of pigment discoloration was determined. Contrary to the expectation that lower wavelength photons induce more damage than higher wavelength ones, UV (394?nm), blue, and cyan light all lead to similar levels of discoloration of a pigment for the same level of radiant power. By understanding this wavelength dependence, it becomes possible to create white light LED lamps with a spectral composition tuned to minimize the degradation effect. An existing LED solution with a modified emission indeed resulted in 30% less color change in the experiment than halogen. Furthermore, a method is proposed to optimize the LED spectra by tuning to the properties of each specific artifact. Simulations show that this can reduce the damage of the light source by 45% in specific cases.     

Reflections on light monitoring: Evaluating museum lighting options for modern and contemporary art

Spectrometric handheld light meters that can provide adequate data for evaluation of replacement bulbs for contemporary art objects are now commercially available. This approach was taken to assess potential replacements for the incandescent street lamps in Chris Burden's Urban Light at LACMA, Los Angeles, USA. These meters are also useful tools for monitoring and characterizing museum lighting, which are currently done with illuminance (lux) meters. The new spectral light meters will enable conservators to tailor lighting recommendations for individual artworks, when spectral information from these meters is combined with damage function data on artists’ materials. The latter information can be obtained for some materials by a small modification to the microfade testing procedure, as exemplified by microfading colored samples Henri Matisse created during the design phase for La Gerbe.     

Spectroscopic Analysis of Colorants Used for bachiru Carving Technique Found in the Shosoin Treasures

The Shosoin treasures, which include the belongings of Emperor Shomu (CE 701–756) and Empress Komyo (CE 701–760), have an honorable origin and have been continuously handed down for generations since the eighth century in the Todaiji temple in Nara, Japan. Some of the beautiful artifacts found among the treasures display the bachiru carving technique, in which a delicate pattern is produced by carving dyed ivory or antler using additional painting. To elucidate the colorants used for dyeing and painting in the bachiru technique, non-invasive scientific analyses using fiber optic reflectance spectrometry in the visible region, X-ray fluorescence spectroscopy, and X-ray diffraction were performed for eight treasures: a go game board, two go pieces, a nyoi (ritual nail pole), a kugo harp, a bird-shaped accessory, a kaburaya arrow, and a ritual ruler. Second derivatization of the reflectance spectra led to characterization of the dyes in the treasures as sappanwood, lac, madder, gromwell, and indigo. Lac and atacamite were respectively identified in the red and green areas of the painting by reflectance spectrometry and X-ray diffractometry. These results indicated the use of a variety of colorants for the bachiru carving technique in the eighth century.     

'Diasec' and Other Finishing Techniques - Investigation of Accelerated Light Fading

Abstract

A study of the accelerated light fading behavior of face-mounted color photographic materials has shown that alterations on the surface of the materials influence their fading characteristics. With the help of spectral density measurements it became apparent that the application of materials such as silicone rubber, adhesive film and acrylic sheeting, but also laminating films, onto the surface of the prints accelerated the degradation of the colorants, especially the yellow dye, in chromogenic materials. In the case of silver dye bleach materials, however, the opposite effect was observed. The influence of the material combination on the stability of face mounted color photographic prints was demonstrated to vary considerably. In order to better assess the inherent damage potential of the materials themselves, these were examined by means of instrumental analysis and measurements of pollutant gasses. Besides off-gassing compounds such as acetic acid and changes in pH caused by aging of the adhesive, face-mounting with a rigid plastic sheet (acrylic glazing) also affected the respective fading behavior of the various materials that were tested.     

知识产权请求权在信息资源数字化过程中的实现

主要探讨知识产权请求权在信息资源数字化过程中如何实现。阐述知识产权请求权制度的基本内容;论述如何在信息资源数字化的过程中实现知识产权的请求权;指出在知识产权请求权实现过程中应该注意的问题,并为建立和完善知识产权请求权制度提出建议。     

Spectral Characteristics of Chemically Weathered Sandstones in the Yungang Grottoes,China

ABSTRACT

Many of the sandstones at cultural heritage sites around the world are susceptible to chemical weathering, and long-term monitoring of the chemical weathering would be of great value for heritage conservation and would also provide reference data for environmental protection policies and projects. Reflectance spectroscopy is a potential tool for monitoring sandstone weathering due to its non-destructive characteristics. In this paper, we present the results of an investigation into the reflectance spectra of sandstones at the Yungang Grottoes, China, where the sandstones are variously fresh, calcite-dissolved, or argillitic-altered. We found several spectral absorptions, including those at 490, 675, 900, 1410, 1918, 2205, 2330, 2350, and 2380?nm. The absorptions at 490, 675, and 900?nm are related to hematite cement, while that at 2330?nm is associated with calcite cement. The absorptions at 1410, 2205, 2350, and 2380?nm are induced by the Al–OH vibration of kaolinite, and that at 1918?nm is related to crystal water. The calcite-dissolved sandstones have lower absorption intensities at 2330?nm than fresh sandstones, and the argillitic-altered sandstones have lower absorption intensities at 490, 675, and 900?nm than the fresh sandstones. In the 1st-derivative reflectance plots, the absorption peaks at ～1400?nm shift towards shorter wavelengths with increasing kaolinite contents. The spectral features of the fresh, calcite-dissolved, and argillitic-altered sandstones are all different, and this means they can be distinguished spectroscopically, which demonstrates the usefulness of reflectance spectroscopy for the long-term monitoring of sandstone weathering in the Yungang Grottoes.     

New insights into brazilwood lake pigments manufacture through the use of historically accurate reconstructions

A multi-analytical approach for the study of brazilwood and its lake pigments was carried out based on historically accurate reconstructions. Recipes for brazilwood lakes from the fifteenth century technical text Livro de como se fazem as cores and the Winsor & Newton nineteenth century colourman's archive were reproduced and compared. Both primary sources allowed for the successful preparation of brazilwood lake pigments with colours that vary from light pink to dark red. The main steps and ingredients for the manufacture of these pigments were common in both sources, particularly the addition of Al³⁺ in the form of alum, and calcium carbonate (chalk). Reconstructions revealed that the latter acts as a pH buffer and filler, controlling the pH at which the lake pigment precipitates. The main difference between the two sources is that the nineteenth century recipes give the quantities for all ingredients, the precise temperatures and time, and achieved higher relative pigment yields (75% versus 45%). Full chemical characterisation of the reconstructions provided detailed information on the individual steps in the pigment manufacture and revealed that the presence of calcium sulphate dihydrate (gypsum) in the final pigment was a result of its formation in situ. Infrared, reflectance, and fluorescence spectroscopy proved to be essential and complementary techniques: while infrared was used to characterise additives and binders, reflectance and fluorescence data were fundamental for identifying the chromophore. The pigments and paints produced can now be used as standards for the identification and investigation of brazilwood lake pigments found in artworks.     

基于RDF的异构信息语义集成研究

建立Web信息源集成系统的目的是为用户提供多异构信息源的统一查询机制 ,让用户像使用一个大数据库一样 ,用统一的方式使用来自不同数据源的各种数据。本文提出的结构旨在开发数据语义 ,以对集成的异构信息源提供一个连贯的、有意义的视图。本结构为确保模块性分成五个独立层 ,并对每一层提供定义、要求和接口。相对数据仓库而言 ,它的数据更有利于松散型检索式。该结构的创新之处在于把语义驱动和按需驱动检索的方式结合起来。这种方式既带来许多优点 ,也包括许多挑战 ,这些我们都与该结构的底层模型RDF进行对比讨论     

Social Science Sponsored Researchers

This study examined the use of academic libraries by academic sponsored researchers in the social sciences at five universities in the greater Boston area. It provides information about researchers use of the library during the proposal development and research stages; it inquires into other information sources employed by the researchers; and it collects data about the types and ages of information materials used in support of the respondent's research projects. Analysis of the responses indicates that for the majority of the researchers, the library was used between one and five times during their proposal development work but that the resources of the library were not a factor in the development of their research proposals. While the researchers indicated that they had used or expected to use their campus libraries as well as other libraries during the course of their research, they also expected to obtain research related information from other sources. They ranked their personal collections first in importance as the place they turned to for information materials in support of their research activity, with their campus library or libraries ranked second.     

Media Reference Sources for an Academic Library

Summary

On the surface many media reference questions seem simple to answer. However, the lack of reference tools often hinders the reference librarian's ability to answer even the most straightforward query. In some cases, the library simply has an inadequate collection, lacking necessary sources. In other cases, the reference tools simply do not exist. Experienced academic media librarians develop toolkits, consisting of published sources and Internet sources that allow us to provide quality reference service, despite the challenges. The appended annotated bibliography represents one librarian's media reference toolkit. Although some of the sources will vary from library to library, many of these sources are essential to effective media reference work regardless of the Specific institution.     

投资者信息行为分析:信息源的选择与利用研究

文章采用案例研究与半结构化深度访谈法研究个体股票投资者信息搜寻过程中信息源的选择和利用。通过开放编码和描述性统计对数据进行定性和定量分析。研究发现,财经网站、电视及投资者自身是投资者的主要信息来源;质量、数量、时间及个人内在因素是投资者选择和利用信息源时考虑的主要维度;而方便性、客观可信性、权威性、使用习惯等则是用户选择信息源时遵循的主要标准。投资经验、投资知识和投资模式一定程度上影响用户信息源选择;信息源的选择和利用与投资者的投资成功与否有一定关系。     

Evaluation of Internet Information Sources by High School Students in Ghana

The Internet clearly presents the opportunity for students to expand their knowledge at a fast pace, since they are able to access enormous amount of information. However, accessing the Internet also has its downside since not all information is of good quality. The study explored how 12th grade students at a high school in Ghana evaluated online information sources. These students and the head of the Information Communication Technology department respond to self-administered questionnaires and a semi-structured interview, respectively. The study found that most of the high school students did some kind of an evaluation of online information sources, however, they were not applying the right criteria. The study further revealed that students were not introduced to evaluation criteria at school and this had contributed to the gap in their evaluation competencies.     

当代网络参考源的类型与特征分析

目前,网络参考源的类型主要有两大类:有传统工具书依托的网络参考源和无传统工具书依托的网络参考源。它在形式、内容、价格和检索系统等方面,与传统印刷型参考源相比,都具有很大优势。表4。参考文献10。     

Citation Needed

The ability to add hyperlinks to a news story is a key feature of online news. In addition to the—aging—technical novelty, one can wonder what functions hyperlinks perform in news stories. Previous research, as well as my previous examination of meta-journalistic discourses, has shown that one of the alleged functions of links is to display the writer's sources. In that sense, hyperlinks are “journalistic objects of evidence” as they can directly point to the documents, data or discourses used as rough material for a news story. The present paper puts that particular function of hyperlinks to the test. It conducts a content analysis on a sub-sample of the stories published on six Belgian news sites that contain at least one external link, and compares the links with the sources explicitly mentioned in the news story itself. Results highlight that links and the mentions of sources do not overlap completely. Many sources are not reflected in links, and most links do not point to primary sources per se. Other functions of links emerge, such as providing a service or contextual information to the readers. These findings thus question the material nature of “journalistic objects of evidence” and the possibility for journalists to build networks of distributed responsibility with links.     

Electronic Stacks

Summary

The awareness of Web sources in reference service has risen in recent years as many reference librarians have become more Internet-minded. During the reference process, we often ask ourselves: can this question be answered by using the Web?

The use of Web sources is expanding the amount of available reference information, enhancing individual libraries' collections, and, hence, providing better user service. There are many benefits in using the Web sources in reference service. There are also some drawbacks. Some useful Web sources are reviewed.

The Web, when used properly, provides reference librarians with a valuable resource option to help improve their services in an effective manner.     

Overview of preventive conservation and the museum environment in China

Based on a nationwide investigation of the current state of preservation of museum objects in China, around 51% of the 35 million museum objects show different degrees of deterioration. Although treatment of objects is necessary, treatment alone is not sufficient. In China's present situation, preventing damage to museum objects is much more cost-effective than allowing damage to happen and then treating it. The number of museums in China is increasing very fast: 23?000 exhibitions are held, 600 million visits are made, and 35?000 archaeological objects are excavated nationwide, each year. At the same time, these museums are widely distributed and have different levels of resources. We need both technical knowledge and preventive conservation to safeguard our precious museum objects. This paper introduces research achievements in preventive conservation, and traces the development of this discipline in China. Starting from the classification of museums in China, legislation is detailed on preventive measures such as selecting appropriate light sources, controlling temperature, relative humidity, light damage, and pollutants. This paper describes achievements in monitoring, analysis, evaluation, and control of museum environments in China. It also proposes future directions for museum environment studies during China's twelfth Five-Year Plan.