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Abstract In museums, silk cultural relics are highly sensitive to light. However, lighting is inevitable due to the exhibition needs, despite any light would pose irreversible damage to silk. Although the solution of eliminating UV radiation was widely achieved in museum lighting environment, long-time accumulation of other light sources still would induce photodegradation of silk. This work therefore established the simulated light ageing experiments to assess the degradation behaviors of silk samples with different ageing degrees. The variation of color values and structure transformation of each sample group were determined by the means of scanning electron microscopy (SEM), colorimeter, Fourier Transform infrared spectroscopy (FTIR) and 13C CPMAS NMR. The results indicated that silk samples with different initial ageing degrees presented different discoloration tendency and structural variation in experimental lighting environment, suggesting the higher disordered structure makes the silk more vulnerable to light damage. It is of great significance to understand the long-time impacts of illumination on degraded silk and further provide methodology for predicting the duration of exhibited silk cultural relics.

Asphalt roads and waterproofing membranes on roofs are exposed to sunlight, which induces irreversible changes in those materials. The underlying chemical processes initially affect the surface but later on impact the bulk chemistry and the mechanical properties. Bitumen, the binding and sealing material, is particularly susceptible to such influences. However, the molecular processes that initiate material deterioration are still poorly explored. Here, we show that ultraviolet and visible light cause the formation of a unique set of oxidation products and alter aromatic structures on the bituminous surface. Qualitative and quantitative information is obtained using infrared, fluorescence and NMR spectroscopy. Bulk ageing studies have shown a shift of molecules from the aromatics to the resins and asphaltenes fractions, potentially influencing colloidal stability. The evaluation of surface processes was facilitated in ageing studies with thin sub-µm specimens. We find that gaseous oxygen is essential for molecular changes to occur. The formation of carboxylic acids, esters and aliphatic alcohols, coupled with the degradation and restructuring of aromatic systems, demonstrates the unique nature of light ageing. This is due to a nuanced interplay between oxidation, degradation, condensation and aromatisation reactions. The ageing rates depend on the origin of the binder and increase as the wavelength of the light source decreases. Ageing follows an asymptotic growth with time. All results considered, this study enabled us to decipher critical molecular processes during photochemical ageing. In this regard, we hope to develop more effective strategies for mitigating and preventing the adverse impact of solar radiation on bituminous infrastructure in the future. • Thin-layer analysis facilitates the exploration of ageing on the bitumen surface. • Photo-induced ageing causes molecular processes not observed in thermal ageing. • Oxidative gaseous species are required for reactions to take place. • Asphaltenes remain (almost) unaltered during light-ageing. • Drivers of molecular changes are mainly found in the aromatics and resins fractions. [ABSTRACT FROM AUTHOR]

Two aspects of consolidation of powdery paint layers are discussed in this paper: First, the colour stability of different consolidation media including cellulose and protein based materials was evaluated. Film sheet samples of the adhesives were exposed to a Xenontester for 276 hours to reach Blue Wool Standard 7. Light exposure caused loss of colour rather than yellowing in most adhesives which correlates to microfading tests. Secondly, colour changes of the pigment layer during application of consolidation media with an aerosol generator were examined. Any shift of colour results in a change of surface structure rather than a detectable shift seen in the ΔE*ab- values and the reflectance graphs. Thus, the application of aerosols is a very controllable, long-term stable method and results only in minor changes when applied in multiple layers. [ABSTRACT FROM AUTHOR]

To guide conservators in their decisions in active conservation of polystyrene materials, seven adhesives were tested before and after light ageing. The material was investigated by assessment of working properties, appearance, colour measurement, tensile testing, hardness measurement, assessment of break type, scanning electron microscope imaging, and assessment of reversibility. Based on a survey among conservators, the adhesives included were acrylates (Paraloid® B-72 in acetone: ethanol, or only ethanol, Paraloid® B-67 in isopropanol, Primal® AC 35, Acrifix® 116), epoxies (HXTAL®-NYL-1, Araldite® 2020) and one cyanoacrylate (Loctite® Super Attack Precision). Adhesives were tested on extruded sheets of transparent, general purpose polystyrene applied on joined edges and as an open layer. Damage to the plastic could be seen for Acrifix® 116 and Loctite® Super Attack Precision. The average break force sensitivity values indicate that the cyanoacrylate was weakened while Acrifix® 116 was strengthened after ageing. In general, the cyanoacrylate was the strongest and Paraloid® B-67 the weakest. Most adhesives showed yellowing after ageing apart from Acrifix® 116 and HXTAL®-NYL-1. The Paraloids, Primal® AC 35, and the epoxies were possible to remove from the plastic. [ABSTRACT FROM AUTHOR]

In this paper a non-invasive quantitative multi-spectral imaging technique was used for monitoring the degradation of parchment caused by light exposure. The parchment samples were aged for 24, 48, 72 and 120 hours in a weather-ometer ageing chamber to simulate a long term sunlight exposure. The effect of light exposure when a ultra violet (UV) filter is used was investigated. The degradation was monitored by using Light Emitting Diode (LED) multi-spectral imaging coupled to multivariate statistical methods and infrared spectroscopy, gas chromatography-mass spectrometry (GC-MS) and thermo-gravimetric analysis (TGA) techniques in order to elucidate the mechanism of the parchment ageing and to correlate chemical and imaging data. A description of the effect of light exposure is given: the degradation of collagenous phase and thermo-oxidative phenomena are not involved in the photo-oxidation process and, as expected, the UV radiation accelerates the ageing effects. Moreover the non-invasive imaging methods used for the detection of ageing and the monitoring o f the conservation state of the parchment surface were able to identify the non-visible degradation long before possible detection by other common analytical techniques. [ABSTRACT FROM AUTHOR]

In the late nineteenth and early twentieth centuries silks processed in Europe were frequently weighted with tin phosphate/silicate. There is particular concern over these silks in collections, since they appear susceptible to catastrophic deterioration. The aim of this research was to better understand the consequences of tin weighting on the ageing behaviour of silk, and so inform preventive conservation policies for these artefacts. Samples treated according to two authentic procedures, 'pink tin' and 'dynamite', were prepared and characterized. The mechanical performances of the silks were then assessed before and after artificial ageing. Environmental scanning electron microscopy energy dispersive X-ray spectroscopic (ESEM-EDS) analyses of the treated samples suggest that pink tin-weighted silks incorporate sodium tin(IV) phosphate with some tin(IV) oxohydroxide, while dynamite tin weighting provides a complex sodium tin(IV) aluminophosphosilicate inclusion. The mechanical strength tests reveal that although the weighted silk samples were weaker than untreated silk after their initial weighting treatment, there was a smaller decrease in strength than expected after ageing. This suggests that the long-term stabilities of the tin-weighted silks may be somewhat less problematic than previously considered, which may lead to a reassessment of current preventive conservation strategies. Resume «Comprehension du comportement au vieillissement des soies empesees a l'etain des dix-neuvieme et vingtieme siecles» A la fin du dix-neuvieme siecle et au debut du vingtieme siecle, les soies fabriquees en Europe etaient frequemment empesees avec du phosphate/silicate d'etain. Il y a une inquietude particuliere pour ces soies conservees dans les collections, car elles semblent susceptibles de deteriorations catastrophiques. Le but de cette recherche etait de mieux comprendre les consequences de l'empesage a l'etain sur le comportement de la soie apres vieillissement, et ainsi d'eclairer les politiques de conservation preventive pour ces objets. Des echantillons traites selon deux methodes authentiques, celle de « l'etain rose » (pink tin) et celle « dynamite » (dynamite), ont ete prepares et caracterises. Les comportements mecaniques des soies ont ete evalues avant et apres vieillissement artificiel. Les analyses des echantillons sous microscope electronique a balayage environnemental couple a l'analyse X par dispersion d'energie (ESEM-EDS) suggerent que les soies empesees avec l'etain rose comprennent du phosphate d'etain (IV) et un peu d'oxohydroxyde d'etain (IV) tandis que l'empesage a l'etain dynamite fournit un complexe aluminophosphosilicate d'etain (IV). Les tests de resistance mecanique ont revele que bien que les echantillons de soies empesees etaient plus faibles que ceux de soies non traitees, apres leur traitement d'empesage initial, la diminution de leur resistance apres vieillissement etait plus faible qu'on ne l'attendait. Ceci suggere que la stabilite a long-terme des soies empesees a l'etain pourrait etre moins problematique qu'on ne l'estimait auparavant, ce qui pourrait conduire a une reevaluation des strategies de conservation preventive. Zusammenfassung „Das Alterungsverhalten von Zinn-beschwerten Seiden aus dem neunzehnten und zwanzigsten Jahrhundert“ Im spaten neunzehnten und fruhen zwanzigsten Jahrhundert wurde Seide, die in Europa verarbeitet wurde, haufig mit Zinn-Phosphat / Silikat beschwert. Es besteht spezielle Besorgnis fur diese Seidenstoffe in Sammlungsbestanden, da sie besonders anfallig fur katastrophalen Zerfall zu sein scheinen. Das Ziel dieser Forschung war es, ein besseres Verstandnis der Auswirkungen von Beschwerung mit Zinn auf das Alterungsverhalten von Seide zu erlangen, um Richtlinien zur praventiven Konservierung dieser Artefakte zu erstellen. Proben wurden nach zwei authentischen Verfahren, „rosa Zinn“ und „;Dynamit“, hergestellt und charakterisiert. Die mechanischen Eigenschaften der Seide wurden dann vor und nach der kunstlichen Alterung beurteilt. Rasterelektronenmikroskopie Energiedispersive Rontgenspektroskopie (Environmental scanning electron microscopy energy dispersive X-ray spectroscopy (ESEM-EDS))- Analysen der behandelten Proben zeigen,dass „rosa Zinn“-beschwerte Seide Zinn (IV)-Phosphat mit einigem Zinn (IV) Oxohydroxid beinhaltet, wahrend eine Beschwerung mit „Dynamit“ zu einer komplexen Zinn (IV) Aluminophosphorsilikat Verbindung fuhrt. Versuche zur mechanischen Festigkeit zeigten, dass zwar die beschwerten Seiden-Proben direkt nach der Beschwerung schwacher waren als unbehandelte Seide, jedoch nach der Alterung eine wesentlich geringere Verschlechterung der Festigkeit festzustellen war als zuvor vermutet. Dies deutet darauf hin, da&ss die langfristige Stabilitat der Zinn-beschwerten Seide vielleicht etwas weniger problematisch ist als bisher angenommen, was zu einer Neubewertung der derzeitigen praventiven Konservierungsstrategien fuhren konnte. Resumen “Entendiendo el comportamiento de envejecimiento de sedas cargadas con estano de los siglos XIX y XX” A finales del siglo XIX y primeros del XX las sedas procesadas en Europa se cargaban frecuentemente con silicatos y fosfatos de estano. En el contexto de colecciones hay una preocupacion especial por estas sedas ya que son susceptibles a deterioraciones catastroficas. El objetivo de esta investigacion fue el entender mejor las consecuencias de la carga de estano en el comportamiento de envejecimiento de las seda, para poder elaborar planes de conservacion preventiva para estos artefactos. Se prepararon y caracterizaron muestras tratadas siguiendo dos procesos autenticos: 'estano rosa' y 'dinamita'. Se evaluo el rendimiento mecanico de las sedas antes y despues del envejecimiento artificial. Los analisis de las muestras tratadas usando tecnicas de microscopio electronico de barrido ambiental rayos X de dispersion espectroscopicas (ESEM-EDS), sugieren que las sedas cargadas con 'estano rosa' incorporan fosfato de estano(IV) con algo de oxohidroxido de estano(IV), mientras que las cargadas con 'dinamita' proporcionan la inclusion de un complejo de aluminiophosphosilicato de estano(IV). Las pruebas de fuerza mecanica revelaron que a pesar de que las muestras de seda cargadas eran mas debiles que las de las sedas que no habian sido tratadas despues del tratamiento inicial, despues de ser envejecidas habia menos disminucion en fuerza que lo que se esperaba. Esto sugiere que la estabilidad a largo plazo de las sedas cargadas con estano puede ser menos problematica de lo que se habia considerado en el pasado, lo que puede llevar a reconsiderar las estrategias actuales de conservacion preventiva. [ABSTRACT FROM AUTHOR]

The assessment of the influence of natural and artificial ageing on the spectrofluorescence of triterpenoid varnishes dammar and mastic is the focus of this work. Both Fourier transform infrared (FTIR) microscopy using attenuated total reflectance and Raman spectroscopy have been employed for complementary molecular analysis of samples. Synchronous fluorescence spectroscopy, excitation emission spectroscopy, and statistical analysis of data have been used to monitor changes in the optical properties of varnish samples. Assessment of naturally and artificially aged samples using excitation emission spectroscopy suggests that extensive exposure to visible light does not lead to easily appreciable differences in the fluorescence of mastic and dammar; cluster analysis has been used to assess changes, which occur with artificial ageing under visible light, indicating that differences in the fluorescence spectra of aged triterpenoids may be insufficient for their discrimination. The results highlight significant differences between the initial fluorescence of films of dammar and mastic and the fluorescence, which develops with ageing and oxidation, and specific markers, which change with ageing in FTIR and Raman spectra, have been identified. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]