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Spectral damage model for lighted museum paintings: Oil, acrylic and gouache
Abstract
A spectral aging test was developed to estimate the photochemical damage of oil, acrylic and gouache paints exposed to permanent lighting. The paints were irradiated at seven different wavelengths in the optical range to control and evaluate their spectral behaviour. To reach this objective, boxes with isolated aging cells were made. In each of box, one LED of a different wavelength and one photodiode were installed. Inside the boxes, the temperature of an exhibit area was recreated through a thermocouple sensor that controlled the temperature using a fan. The heat produced by the LED was dissipated by a thermal radiator. Moreover, to evaluate the exposure time dependence of the irradiation level, the test was performed using two different irradiation levels in ten exposure series. After each series, the spectral reflectance was measured, and the data collected for each paint and wavelength were used to develop a model of damage produced by the interaction between the spectral radiant exposure and the paint.
... The detailed reaction kinetics need to be known to make display lifetime predictions. To obtain rough estimations, data bases of materials tested with specific light sources can predict the average damage potential of light sources for a specific class of materials [11,12]; however, such predictions often fail for specific materials or for light sources that are very different from those in the data set. ...
... Several research groups [12,24,25] have investigated the damage potential under narrow band LED exposure comparable to this study. However, the studies do not proceed to determine sensitivity curves and action spectra and do not make a quantitative prediction for white LED exposures. ...
... However, the studies do not proceed to determine sensitivity curves and action spectra and do not make a quantitative prediction for white LED exposures. The authors of [12] investigated the relative damage for oil, acrylic and gouache and develop a spectral damage model, which aims to predict color shifts on the painting over time. The model does not predict color changes for light exposures with very different RSI. ...
(1) Background: The use of light-emitting diode (LED) lighting is increasingly replacing traditional light sources in museums. There is a need to anticipate the damage caused by LED lighting to photographic prints. The aim of this study is to quantitatively predict fading on three inkjet color patches exposed to different white light LED; (2) Method: The novel approach of this work is to measure the wavelength-dependent photochemical efficiency on color patches using a narrow band LED. First, the color patches are exposed to narrow band LED lamps in a proprietary light chamber. Sensitivity curves are obtained by plotting the density changes caused by narrow band exposure as a function of the exposure. In the second step, action spectra are derived from the slopes of the sensitivity curves. The action spectra correspond to the rates of change of a color patch to exposure with different wavelengths of light. In the third step, the narrow band light emissions are fitted to the emission spectra of the white LED of interest. The fitting factors are used to calculate the weighted sum of the density changes; (3) The method predicts the absolute density change of color patches for several white light LED exposures.
... [14][15][16][17][18][19] Other related investigations tried to predict the impact of light exposure in terms of fading or general decay. [20][21][22][23] Particular interest was addressed to painting materials, where pigments and dyes are the components most subjected to fading or decay due to their ability to absorb light. Pigments and dyes are actually substances with a selective spectral absorption as a consequence of their complex molecular structure. ...
... To monitor the processes that can activate, support or accelerate these photochemical reactions in the most reliable way, one can measure physical changes through reflectance spectrometry 23 or colourimetry or even with alternative methods such as microfading testing 17 or reflectance transformation imaging 33 . ...
... Other studies have exclusively focused on the energy saving benefits of optimized lighting systems using daylight and LEDs. 43,23 Another interesting application of these methods is the restoration of faded colourants found in museum objects using customized lighting sources. 36,39,44,45 It is worth highlighting that the approach of inpainting with light implemented by Stenger and co-workers 45 has important implications regarding the need for carrying out a traditional conservation intervention, which would involve cleaning and conventional inpainting. ...
Lighting is a critical component in a museum environment because, together with temperature, relative humidity and pollutants, it is one of the damaging factors able to produce long‐term, cumulative and irreversible photodegradation processes. To correctly preserve artworks, limiting illuminance and exposure is recommended, allowing on one side the preservation of the object, but on the other limiting the display of the object, especially for sensitive materials. The aim of this research was to develop, evaluate and compare a new lighting method for paintings and other cultural materials to improve the experience of the objects whilst reducing the risks from exposure. The idea is based on the use of selective chromatic light where the component of the spectrum absorbed by the materials is removed. This absorption is the principal cause of photodegradation. The proposed lighting system can be obtained by combining different types of projection systems together with filtering using an appropriate light source. Six methods of light projection have been compared for two mock-ups simulating real artworks with high and medium light sensitivity. The efficiency of illumination increased from 30% to 111% compared to standard lighting systems. Light stability tests were additionally performed, finding reduced colour changes compared to traditional lighting systems.
... [14][15][16][17][18][19] Other related investigations tried to predict the impact of light exposure in terms of fading or general decay. [20][21][22][23] Particular interest was addressed to painting materials, where pigments and dyes are the components most subjected to fading or decay due to their ability to absorb light. Pigments and dyes are actually substances with a selective spectral absorption as a consequence of their complex molecular structure. ...
... To monitor the processes that can activate, support or accelerate these photochemical reactions in the most reliable way, one can measure physical changes through reflectance spectrometry 23 or colourimetry or even with alternative methods such as microfading testing 17 or reflectance transformation imaging 33 . ...
... Other studies have exclusively focused on the energy saving benefits of optimized lighting systems using daylight and LEDs. 43,23 Another interesting application of these methods is the restoration of faded colourants found in museum objects using customized lighting sources. 36,39,44,45 It is worth highlighting that the approach of inpainting with light implemented by Stenger and co-workers 45 has important implications regarding the need for carrying out a traditional conservation intervention, which would involve cleaning and conventional inpainting. ...
... Prowadzi on do nieodwracalnych strukturalnych, objawiających się żółknięciem papieru, blaknięciem kolorów, rozkładem spoiw i werniksów, pękaniem i kruszeniem się papieru oraz tkanin [6,9]. Siła negatywnego oddziaływania światła zależy od [3,6,7,8,[12][13][14][15] • W Polsce od kilkudziesięciu lat stosowane są tzw. normy konserwatorskie, określające optymalne warunki mikroklimatu w muzeach. ...
... eKologIa a budownICTwo efekt i skupić uwagę przede wszystkim na dziełach sztuki, podczas gdy jaśniejsze otoczenie ukazuje także przestrzeń wnętrza oraz prowadzi do wytworzenia bardziej swobodnej atmosfery [21]. W celu osiągnięcia kompromisu między wymogami konserwacji muzealiów i wrażeniem wzrokowym odbiorcy, a także zapewnienia możliwie wysokiej efektywności energetycznej, oświetlenie typu smart powinno realizować następujące cele sterowania [6][7][8]12]: priorytetowe wykorzystywanie światła dziennego (na- Zasadniczo funkcje automatycznego sterowania oświetleniem mające na celu ograniczenie zużycia energii są zgodne z wymaganiami konserwacji zabytków, gdyż ich oddziaływanie polega na ściemnianiu lamp lub ich całkowitym wyłączaniu, gdy oświetlenie nie jest potrzebne. ...
Muzea charakteryzują się najbardziej wymagającymi kryteriami oświetleniowymi spośród wszystkich budynków. W artykule przedstawiono charakterystykę technologii oświetlenia typu smart (tzw. inteligentnego), w kontekście zastosowania w budynku muzeum i dążenia do kompromisu pomiędzy ochroną zbiorów, potrzebą ich udostępniania publiczności i niskim zapotrzebowaniem na energię.
... Today, available technology allows adopting a more sophisticated design approach, accounting for the spectral sensitivity of lit objects. Thanks to the use of multichannel LED systems, it is possible to obtain ad-hoc spectra (Dang et al. 2019;Pinilla et al. 2016) limiting the energy content at wavelengths corresponding to the maximum sensitivity of the materials. Of course, the final spectrum should be optimized to guarantee a high color rendering index, without reducing the overall quality of light. ...
... In another study, Dang et al. (2019) proposed a method to optimize the spectrum of a 4-channel LED, in order to obtain a protective source considering the sensitivity of the pigments in the works of art, accounting also for the color rendering. Moreover, Pinilla et al. (2016) investigated how light exposure with different spectra obtained with a multichannel LED determines color changes of the paintings. In this case, a 7-channel LED was used, but no advanced photo-biological or chemical analyses were conducted. ...
Exposing artworks and artifacts in museums is fundamental to disseminate culture and knowledge but is also risky since the exposure to environmental conditions can deteriorate exhibited objects.Light is crucial, being able to trigger photochemical effects, and jointly responsible (with tem-perature and humidity) for biological risk generation. In this context, fungal growth in museumartifacts is a damaging factor that should not be underestimated. Consequently, the study oflighting effects on fungi development is essential. In this work, five different fungal strains(Aspergillus fumigatus, Bjerkandera adusta, Fusarium oxysporum, Penicillium chrysogenum, andPenicillium granulatum) isolated from samplings on animal exhibits hosted in the ZoologicalMuseum of Naples, Italy, are cultivated inside four experimental boxes, equipped with monochromatic LEDs with different peak wavelengths (460 nm, 518 nm, 594 nm, and 638 nm). The growth rate, the protein and carbohydrate contents are analyzed and compared to results obtained indarkness (typical growth conditions for studies about fungi). Results demonstrate that, even if fungi are heterotrophic organisms and do not need light to grow and develop, their growth rate and their protein and carbohydrate contents are affected by exposure to monochromatic radiation, but the spectral sensitivity strictly depends on the analyzed species. For this reason, it is not possible to infer general practical guidelines for lighting applications, and it becomes urgent to establish accurate and shared analysis protocols to be applied case by case, to study the effect the environmental conditions on microorganisms and drive-specific design choices
... This type of damage is often gradual and can significantly alter the visual and structural integrity of paintings over time. The primary causes of chemical deterioration include environmental pollutants [43] and light exposure [44]. ...
... Organic pigments are particularly sensitive to light, undergoing noticeable color changes, while light exposure also triggers oil oxidation, further accelerating deterioration. Santiago et al. [44] exposed paints to seven different wavelengths in isolated aging cells equipped with LEDs and photodiodes to measure spectral reflectance. Temperature was regulated using thermocouples and fans to simulate exhibit conditions. ...
Oil paintings represent significant cultural heritage, as they embody human creativity and historical narratives. The preservation of these invaluable artifacts requires effective maintenance practices to ensure their longevity and integrity. Despite their inherent durability, oil paintings are susceptible to mechanical damage and chemical deterioration, necessitating rigorous conservation efforts. Traditional preservation techniques that have been developed over centuries involve surface treatment, structural stabilization, and gel-based cleaning to maintain both the integrity and aesthetic appeal of these artworks. Recent advances in artificial intelligence (AI)-powered predictive maintenance techniques offer innovative solutions to predict and prevent deterioration. By integrating image analysis and environmental monitoring, AI-based models provide valuable insights into painting preservation. This review comprehensively analyzes traditional and AI-based techniques for oil painting maintenance, highlighting the importance of adopting innovative approaches. By integrating traditional expertise with AI technology, conservators can enhance their capacity to maintain and preserve these cultural treasures for future generations.
... analysed how lighting affects 23 different pigments in order to develop a system to measure the spectral response of exposed materials. This system allowed estimating the time and the maximum irradiance with which a artwork can be illuminated without noticeable changes in its colour [38]. Stenger (2015) based the lighting of Mark Rothko's murals on the limitation established by the CIE of an illuminance of less than 50 lux, restricting UV and IR radiation [26], since, in addition, one of the artist's requirements was that the artwork not be too illuminated [24]. ...
... With the information from the CIELab coordinates and reflectance information, they developed a merit function based on Fernandez-Balbuena et al. [40] to optimize the E * 00 between the D65 reference and test illuminant. A second merit function was developed in order to minimize the radiation damage through the concept of GRF, developed by Mayorga et al. [32,38]. Using the optimization algorithm, based on Durmus and Davis [36,37] and Muñoz De Luna [28] described above, and the lighting system described by the Zeus Project [30], they calculated the optimal SPD and the intensity of each point in the image [21]. ...
The virtual modification of the appearance of an object using lighting technologies has become very important in recent years, since the projection of light on an object allows us to alter its appearance in a virtual and reversible way. Considering the limitation of non-contact when analysing a work of art, these optical techniques have been used in fields of restoration of cultural heritage, allowing us to visualize the work as it was conceived by its author, after a process of acquisition and treatment of the image. Furthermore, the technique of altering the appearance of objects through the projection of light has been used in projects with artistic or even educational purposes. This review has treated the main studies of light projection as a technique to alter the appearance of objects, emphasizing the calibration methods used in each study, taking into account the importance of a correct calibration between devices to carry out this technology. In addition, since the described technique consists of projecting light, and one of the applications is related to cultural heritage, those studies that carry out the design and optimization of lighting systems will be described for a correct appreciation of the works of art, without altering its state of conservation.
... The extent of the damage that daylight can cause to displayed artifact depends primarily on the lightsensitivity of the exhibited material, the intensity of light that affect it, and the time of display of this artifact. High illuminance levels and long exposure time can accelerate the damage of the exhibited item [22][23][24][25] . There are several approaches to evaluate lighting performance in museums and the potential damage that is caused by daylight on an artifact. ...
... This level came originally from color science that had established that this level was enough to ensure that the human eye was operating well within the range of full color vision. However, it was also discovered later that this benchmark will allow only young people (age 25) to see all the details almost as well at 50 lx as they will in full sunshine within certain conditions (e.g. a moderately light-colored object, with a moderate degree of detail, in a moderately complex pattern, in a reasonable period of time). Unfortunately they will not see the details well if the object is dark, the details are very fine, the pattern is complex, and/or the viewing time is limited. ...
This paper provides a comprehensive process that investigates daylighting performance with regards to museum lighting (adequate lux levels versus safe light exposure) and visual comfort requirements (no glare or sunlight) in the UAE traditional courtyard buildings that were converted into heritage museums. The study used several methods such as site visits, on-site measurements, surveying of architectural drawings, and statistical analysis of design data to examine existing case studies and extract information that helped identify building morphology configurations and define parameters to represent this building typology. The defined configurations helped develop the 3D geometry of the representative model in which the most dominant courtyard and exhibit room ranges were considered. Then, a comprehensive multi-scenario simulation process based on several climate-based daylight metrics under the UAE sky conditions was carried out to investigate lighting adequacy against potential risks on artifacts and visual comfort using several configurations of the developed model. The scenarios included different orientations with different window-to-wall ratios (WWR) of windows looking upon the courtyard using different configurations of the traditional verandah that helped shade the windows and reduce light exposure risks. The performance variables were analyzed against the recommended values/ranges by several international lighting standards. The study recommended several options to enhance the overall lighting environment and minimize risks on artifacts and visual comfort. This included better spatial arrangements, better designing and sizing of openings, and implementation of effective shading systems.
... It is well known that UV components and blue light from artificial museum white LED lighting is itself a degrading agent for paintings, especially when their paint film consists of photosensitive pigments, as in the case of cadmium yellow [15][16][17][18]. ...
The degradation of cadmium yellow in paintings is influenced by various factors, primarily environmental conditions and light exposure. Applying a thin protective layer of linseed oil on the surface could help mitigate these processes. Linseed oil, being a natural material, acts as a barrier against harmful atmospheric agents like moisture and oxygen, which contribute to the degradation of pigments including cadmium yellow. Additionally, linseed oil reduces direct light exposure, thereby lowering the risk of fading and color alteration. In this study, we explored the degradation of cadmium pigments mixed with oil and applied on canvas. We elucidated how the use of a binder prevents the direct oxidation of the pigment, inducing artificial degradation by irradiating samples with UVA (365 nm) and UVC (250 nm) sources. By employing various spectroscopic techniques such as three-dimensional fluorescence mapping (PLE) and Raman, along with colorimetric analysis, we gained a comprehensive understanding of the degradation process, particularly when linseed oil serves as a protective layer.
... The changes in lighting equipment can be challenging for conservators, museum lighting designers and curators to balance the needs of conservation and visibility, and successfully deliver an artist's original intent. 1,[15][16][17][18][19][20] Based on the understanding of the effect of light on art, researchers proposed mathematical models and tool, [21][22][23][24][25][26][27][28][29][30] investigated the optimisation of theoretical and commercially available spectra for conservation using different techniques. 11,14,[31][32][33][34][35][36][37] Among many lighting technologies used to optimise light source spectra, multi-primary LED light projectors offer advantages in spatial and spectral optimisation over traditional architectural light sources ( Figure 1). ...
In this research, three-channel LED-augmented reality projector spectra were optimised for 24 colour samples using a brute-force (BF) and multi-objective genetic algorithm (MOGA). The BF search and MOGA performed similarly in achieving optimal results, reducing both light absorption and energy consumption by almost half. However, MOGA was 2.5 times faster than BF in finding optimal solutions. The results indicate that an LED RGB projector can be used to illuminate museum artefacts to reduce light absorption and energy consumption, with the caveat of perceptible colour shifts in some of the colour samples. Future research will investigate observers’ subjective evaluations of artwork under optimised lighting.
... To our knowledge, most of the related studies tend to focus on colorants by considering their interaction with substrates [10][11][12], with little consideration given to the blank substrate. Liu et al. studied the spectral responsivity of historical paper under irradiation of three narrowband lights by measuring reflection spectra and color difference [13]. ...
As an important supporting material for calligraphy and painting relics in collections, the silk substrate is generally in acidification. And owing to an extremely high light response, it is very prone to different forms of lighting damage, including color and mechanical aspects. Considering that the Light Emitting Diode (LED) with flexible spectral compositions is widely used in the lighting environment of collections, the spectral responsivity of acidified silk substrates is the core issue concerning the long-term conservation of calligraphy and painting relics. In this study, based on the accelerated aging experiment of nine narrowband LEDs with different wavelengths (λ) in the visible range on silk samples with different acidification degrees (pH values), the infrared spectrum was measured non periodically. Processed with the Principal Component Analysis (PCA), the obtained ΔPC1 was used to evaluate the lighting damage of silk samples. Based on the damage change curve, its spectral responsivity function, that is, the mathematical relationship between lighting damage and λ and pH values, was further fitted. Combined with the previous research on the spectral responsivity of colorants, an evaluation method for lighting damage was proposed, which is the key to the conservation of calligraphy and painting relics.
... Problems that arise in museums related to artefacts are damage due to lighting factors [6] [7], due to Indoor Air Quality (IAQ) factors [8], and also acts of looting [9] [10]. Artefact looting is often carried out by irresponsible people who are often transacted on the black market [11]. ...
... [18][19][20][21] There were few studies on HPA materials; however, this type of research provides a reference for the protective lighting of cultural relics. 22,23 In the experimental study reported here, colour difference was measured for nine typical HPA materials, irradiated under 10 different narrowband spectra in the visible light range with different exposure levels. The results were analysed to establish the mathematical relationship (response law) between colour change and exposure for each of the nine materials for each spectral light band in turn, and these individual response laws were then further processed to determine a colour damage equation for each material as a function of both spectral band and exposure. ...
Spectral energy radiated by light sources is the primary source of colour damage in highly photosensitive artworks (HPAs). However, spectral power distributions differ for different light sources, and the absorption and reflection characteristics of different materials, when irradiated by each narrow spectral energy band, also differ. This could result in large differences in the degree of radiation damage for materials under the same lighting intensity. In this paper, the suitability of different light sources used to illuminate HPAs was experimentally investigated over a long period of time by irradiating nine types of typical HPA materials with 10 different narrow-band light sources. By analysing the colour difference data of the illuminated material against the amount of exposure, a mathematical model relating the spectral composition and the damage to the colour of HPA materials was obtained. Based on this, a colour damage evaluation equation for light sources used for lighting HPAs was proposed. Finally, the equations were discussed using an example.
... However, based on the photo-aging experiments of painting materials, that is, oil, acrylic acid, and gouache, Pinilla found that the parameter b changes with aging time. As a result, a mathematical model was established to predict the change behavior of the parameter b [30]. Different from the prediction of the parameter b, Villmann [31] and Dang [32] revised the S(λ) dm,rel in equation (5) into S (λ,t) dm,rel by taking the changes of the reflection spectrum and ΔE* ab of pigments under the irradiation of various narrow-band LEDs as evaluation criteria, respectively. ...
There are needs to consider three requirements of reducing lighting deterioration, improving lighting quality and lighting energy saving for paintings, the high-light-sensitive exhibits in museums whose lighting environment is quite special and complex. Therefore, based on lighting parameters composed of the spectral power distribution of light sources, the spectral response of painting materials, the irradiance or illuminance, and the irradiation time, it is necessary to review researches on paintings in museums from the above three requirements, including the existing research contents, methods, and suggestions.
Based on parameters concerning lighting deterioration, its mechanism and model have been partly clarified and established, following by applications of light sources aiming to better conserve paintings and needing further researches, namely, the lighting deterioration evaluation, the formulation of lighting quantity standards, and the spectral control and adjustment, etc. As for lighting quality, the needs of visitors for colour perception and visual comfort have been evaluated. However, it's urgent to study the model between the lighting quality and its related lighting parameters, which can optimize lighting applications above considering both needs by combining the models of lighting deterioration and lighting quality. The third aspect focuses on lighting energy saving whose strategies involve the replacement and control of energy-saving lamps, mainly for the LED and its spectral control and adjust system, as well as controlling the illuminance and irradiation time.
While expanding the knowledge of paintings in museum lighting for researchers in related fields, this paper emphasizes some remaining issues that can be studied in the future.
... For other applications research activities contributed essential insights to develop optimization strategies. According them are settings tuned to minimize damage of artworks (Mayorga Pinilla et al. 2016), or minimize melatonin suppression for better sleep (Aderneuer et al. 2019). The mentioned art installations point out that not for all effects that metameric lights may cause are straight forward explanations available. ...
Light and lighting in fashion and textile design generally relate to the viewing and production of a fashion or textile collection in daylight, or integrating LEDs, electro-luminescent wires, and optical fibres in the structures of fabrics to create a light-emitting fashion or textile collection. This ignores the potential that coloured light as material for design can bring into these disciplines. This paper aims to investigate coloured light as a material for design in relation both to physical environments and immersive virtual reality, and to develop design methods for fashion and textile design that could lead to a re-learning of coloured light as a material for design for developing novel artistic expressions. The first series of experiments focused on addressing the following questions in both physical and virtual reality: How do coloured surfaces and coloured light interact? How do interactions between coloured surfaces and coloured light influence the process of designing surface patterns? To critically examine the results of this research, textile and fashion design undergraduate students participated in a five-day workshop during which they experimented with, and reflected upon different types of interaction between coloured surfaces and coloured light in both physical and virtual reality. The students’ designs showed that the design method provided them with an understanding of the use of coloured light in their design processes through experimentation and individual exploration, demonstrating that this approach can make a fundamental contribution to the development of coloured light usage in various design disciplines.
... Despite the challenges of facing a universal damage model today, studies investigating the sensitivity of different materials [33][34][35][36][37][38][39][40] can converge into a complex damage appearance model (DAM), similar to color appearance models (CAMs). Although the CIE 1976 L*a*b* (CIELAB) is the most widely used color space in conservation science, the proposed damage model is based on the CAM concept due to the multi-layered nature and better performance of CAMs. ...
Light causes damage when it is absorbed by sensitive artwork, such as oil paintings. However, light is needed to initiate vision and display artwork. The dilemma between visibility and damage, coupled with the inverse relationship between color quality and energy efficiency, poses a challenge for curators, conservators, and lighting designers in identifying optimal light sources. Multi-primary LEDs can provide great flexibility in terms of color quality, damage reduction, and energy efficiency for artwork illumination. However, there are no established metrics that quantify the output variability or highlight the trade-offs between different metrics. Here, various metrics related to museum lighting (damage, the color quality of paintings, illuminance, luminous efficacy of radiation) are analyzed using a voxelated 3-D volume. The continuous data in each dimension of the 3-D volume are converted to discrete data by identifying a significant minimum value (unit voxel). Resulting discretized 3-D volumes display the trade-offs between selected measures. It is possible to quantify the volume of the graph by summing unique voxels, which enables comparison of the performance of different light sources. The proposed representation model can be used for individual pigments or paintings with numerous pigments. The proposed method can be the foundation of a damage appearance model (DAM).
... It is a quantitative evaluation of colour change by detecting the colour coordinates of specimen before and after irradiation and calculating the colour difference values by using the formula. Many scholars have studied the degradation of painting colour by using lighting aging experiments based on colour difference evaluation [18][19][20][21][22][23][24]. However, this kind of research takes exposure as a unified unit and lacks a discussion on illuminance and exposure time, which cannot provide a direct reference for the formulation of lighting quantity indexes. ...
In museum lighting, paintings are the artworks with the highest light sensitivity. They are very vulnerable to irreversible permanent photochemical damage such as fading and discolouration. The basis of effective preventive conservation is to determine the two lighting quantity indexes of illumination and annual exposure. At present, there are some problems such as inconsistent standards, lack of accuracy, and failure to consider protection and visual needs comprehensively. In this study, halogen lamp was used as experimental light source, and 25 pigment specimens were irradiated for 1440 h at four illumination levels. The colour parameters were tested every 240 h and the colour difference was calculated. Based on the data analysis, three-dimensional visual curved surface plots of colour difference ΔE of 25 pigments varying with illuminance I and time t were established, which revealed the colour damage law of different pigments caused by illumination and time. Then, the curved surfaces were fitted into the colour damage evaluation equation set ΔE = fn (I, t) (where n = 1, 2, 3, ..., 25) to establish the damage evaluation model of paintings, which described the damage law of pigments mathematically. Through the above model, the general recommended values of illumination and annual exposure for general painting lighting can be calculated, and the method for obtaining the special recommended values of illumination and annual exposure for precious paintings lighting was given.
... Lighting causes irreversible permanent damage to artworks, such as fading, discoloration, and blackening, which seriously affects the historical and artistic value of cultural relics. [1][2][3] In order to protect exhibits, the International Commission on Illumination (CIE) classifies cultural relics into four levels according to their lightresponsive characteristics. Among them, the dyeable cultural relics based on Xuan paper and silk are of the highest sensitivity and vulnerable to photochemical damage caused by optical radiation. ...
Artworks based on Xuan paper or silk and painted by organic or inorganic pigments are highly responsive to light due to their materials and manufacturing technologies. They belong to the highest level of light responsive exhibits stipulated by International Commission on Illumination (CIE) and are vulnerable to fading and discoloration caused by radiation from light sources. The choice of light sources is the key of protection for artworks. It is indispensible and urgent to choose the lowest damage light sources according to the material characteristics of artworks. In this article, long‐term irradiation of typical light sources on various substrates and pigments was used as experimental method, and CIE DE2000 color difference formula was used as the evaluation index. The laws of the influence of different light sources on the color change of various materials were obtained, and the relative damage coefficients of light sources were calculated. Finally, eight kinds of light sources suitable for illuminating responsive artworks with typical material combinations were proposed. However, there are some limitations in the study, because the ancient Chinese Xuan paper and silk used as experimental objects in the experiment are yellowish. Thus, the models derived in this article are not suitable for choosing reasonable display light sources for other works of art. However, suitable light sources for different materials could be obtained by the calculation method used in this article.
... As carriers of color expression and rich visual artistic effects in high-light-sensitivity art, organic pigments are prone to the illumination-induced damage in the light environment of museums, which manifests as color damage such as fading, discoloration, and color disappearance as well as mechanical damage such as brittleness, powdering, and cracking. At present, color difference is a traditional index to evaluate the influence of illumination on color change in organic pigments [11][12][13][14][15]. However, three limitations of method are as follows. ...
Because commonly used organic pigments are highly responsive to visible light, high-light-sensitivity art is vulnerable to irreversible illumination-induced damage caused by radiation from light sources. With application of the four primary white light-emitting diodes (fp-WLEDs) in museums, it is urgent to evaluate the illumination-induced damage to high-light-sensitivity art caused by the fp-WLEDs. Four narrowband LEDs with different peak wavelengths of 450, 510, 583, and 650 nm that constitute the spectra of the fp-WLEDs were used to irradiate three commonly used organic pigments: safflower, gamboge, and indigo. Based on the fundamental reason for the illumination-induced damage, that is, photochemical reactions, Raman spectroscopy was introduced into the study. The Raman spectra of pigments were measured before and after illumination. The characteristic Raman peaks corresponding to the functional groups that determine color and structure of pigments were selected, and the variations in their peak intensities were calculated. The illumination-induced damage coefficients of four narrowband LEDs on three organic pigments were obtained, providing a data basis for illumination-induced damage evaluation equation proposed in this study, which was expected to further realize museum admission evaluation of the new fp-WLEDs.
... In 1953, Harrison first studied the influence of different wave bands on the damage of materials [10], and obtained the radiation damage curve of materials in the range of visible light with the change of wavelength, but this conclusion was doubted to some extent. The photochemical damage is related to the radiation wavelength, while the absorption and reflection characteristics of different kinds of materials for different wave bands are significantly different [11][12][13][14], so it is difficult to describe the optical radiation damage of different kinds of art materials with the same function. However, the function of the relative damage of paper and silk caused by visible light in different wavelengths has not been obtained. ...
Paper and silk are the artworks with the highest light sensitivity. They are very vulnerable to photochemical reactions caused by the radiation of light sources in museum lighting, resulting in irreversible permanent damage such as color fading and discoloration. The basis of lighting protection for these artworks is to clarify the influence of different light sources on paper and silk materials. In this study, 10 kinds of narrow band monochrome light in the visible light range were used as experimental light sources, real cultural relics paper and silk materials were used as experimental samples, and long-term irradiation experiments were carried out under constant temperature and humidity conditions. The color parameters of paper and silk irradiated by different light sources were detected periodically, and the curve of color difference with exposure was drawn. The relative influence coefficients of different spectral bands on the color of paper and silk were obtained by curve analysis. By fitting data regularity and regression analysis, the “relative damage-spectral composition” function was established. The effect of light source on color damage of paper and silk is described by mathematical language, and the influence formula of different spectrum on color damage of paper and silk is obtained.
... The solution imposes the Wi-Fi technology and IoT [4] for intelligent evacuation guidance systems for improving fire safety (introducing intelligent fire safety), or photoluminescent way finding [5]. The wide range of problems rise from lighting methods in heritage buildings covers also the fresco structural problem [6] or regarding the spectral damage for lighted museum paintings [7] or [8]. The spectral composition has not only negative effect, but also a positive one, as a tool to enhance faded colors of museums artefacts [9]. ...
The heritage buildings generate specific problems for electrical installations, with supplementary request from lighting systems. The continuous trends towards modernization are traditionally in conflict with the conservation of the architectural details. This major constraint must be considered for new circuits, but also for luminaire, when retrofit is the main approach. After the esthetical considerations, the engineering approach raises a problem in connection with the dimensioning methods. For heritage buildings, the lighting systems must cover infinity of situation, very different from classical designing methods, based on Utilization Factor or Direct Illumination Calculus for orthogonal situations. An original method of calculation is proposed, based on analytical geometry, useful for any orientation of the working plane. Even this method has important limitations, generated by the specifically architectural details, and a lighting simulation is necessary. Based on DIALuxEVO7, specific methods are presented. The importance of results interpretation is also underline.
... The paper consisting of plant fibres and silk consisting of protein molecules are used as the substrates of CTPC, both of which are natural organic substances with unstable properties (Proniewicz et al. 2001;Shao et al. 2005). At present, the illumination damage research mainly uses the color difference to evaluate the influence of museum illumination on color fading and discoloration of cultural relics (Dang et al. 2017(Dang et al. , 2018Pinilla et al. 2016;Farke et al. 2016). As non-staining organic substrates, the illumination damage to the substrates is mainly mechanical damage caused by the microscopic molecular structure changes, which cannot be evaluated by the color difference. ...
... Furthermore, Weintraub (2010) found that white phosphor-based LEDs with low to intermediate CCT (2700 K-4000 K) are safe for the illumination of light-sensitive materials, if they are used at appropriate illuminance levels. On the same matter, Pinilla et al. (2016) developed a spectral aging test to estimate the photochemical damage produced by LEDs on oil, acrylic, and gouache paintings; the model they developed provides useful information about the color shift caused by fading and could be used by museums to estimate the ideal exposure time for any painting. ...
Lighting design for art exhibitions has a significant impact on the enjoyment and understanding of the displayed artworks. In particular, the selection of the light sources and the design of the museum space affect the visitors’ visual perceptions of the artworks and their color appearance. This project investigated some of the potential factors—the correlated color temperature (CCT) of the illumination, the overall color content of the painting and the lightness of its background—affecting a painting’s color appearance and appreciation in a museum setting. The study involved a survey conducted in the laboratory with both naïve observers and lighting experts. The CCT of the lighting was found to be the main factor affecting the painting’s appearance and the observers’ overall preference for the lighting arrangements, whereas the overall hue content of the painting and the background lightness had a minor influence. Furthermore, it has been found that the perceived brightness increases along with the CCT.
... At present, the method of color difference is used to evaluate the effect of museum illumination on color fading and the discoloration of pigments in historical artifacts (Dang et al. 2018a(Dang et al. , 2018bFarke et al. 2016;Pinilla et al. 2016). As nonstaining organic substrates, illumination damage to paper and silk is mainly manifested in mechanical damage such as brittleness, chalking, deformation, and cracking, the origins of which are changes in microscopic molecular structure that cannot be evaluated by the method of color difference. ...
As the substrates of traditional Chinese painting and calligraphy, paper and silk are susceptible to optical radiation in museum illumination, resulting in mechanical damage, the origins of which are changes in microscopic molecular structure. However, there is no effective method of quantitatively evaluating the microscopic molecular structural changes caused by irradiation. In this study, Raman spectroscopy was introduced for illumination research on the paper and silk substrates in museums. Four narrow-emitting light sources with different peak wavelengths, red (650 nm), amber (583 nm), green (510 nm), and blue (450 nm), which together constitute the spectrum of a white light emitting diode (LED), were used as experimental light sources. As experimental specimens, paper and silk substrates were irradiated by the four light sources. The Raman spectra of the specimens were collected before and after the illumination. By analyzing the variations in characteristic Raman peak intensities, the relative damage coefficients of the four light sources on microscopic molecular structures in the specimens were studied. Then, we were able to design the white LED spectral irradiance distribution of the two substrates according to the corresponding damage coefficients. In conclusion, a research method for studying the microscopic molecular structural changes in the substrates of traditional Chinese painting and calligraphy based on Raman spectroscopy has been proposed, finding a solution to the long-standing challenge of how to quantitatively evaluate illumination-induced mechanical damage of substrates. These results are instructive for designing the spectral ratios of white LEDs suitable for illumination of traditional Chinese painting and calligraphy in museums.
... The key to protecting TCPs from radiation is the manipulation of the spectral compositions of light sources, where infrared and ultraviolet radiation can seriously damage exhibits [8]; consequently, the elimination of invisible radiation in light sources has achieved a common consensus [9][10][11]. Nonetheless, visible radiation also damages the exhibits and cannot be eliminated because of the required visual effect, so the exploration of the effect of visible radiation appeals to increasingly many researchers [12][13][14][15]. The results of museum investigations [16] at home and abroad by our research group demonstrate that the most frequently used light sources to illuminate TCPs at present are the halogen lamp, which excludes infrared and ultraviolet radiation, metal halide and white LED. ...
Traditional Chinese paintings (TCPs), which are characterized by enormous storage and high value, are prone to suffer radiation damage in museum illumination, such as color fading, discoloration, and even color vanishing, especially for the most light-sensitive traditional Chinese paintings painted with organic pigments (op-TCPs). So, developing the lowest damage light sources is the key to protect traditional Chinese paintings (TCPs). However, color quality of light sources is of great importance as well and there is a lack of methodology to optimize the spectra of light sources for satisfying the protective effect and color quality simultaneously. Here, we showed changing curves of the CIE DE2000 color differences of pigments as a function of the exposure duration by calculating the periodical measured color parameters during the long-term illumination experiment under four monochromatic lights. We deduced relative spectral responsivity functions of op-TCPs by fitting experimental data and obtained the corresponding equal-illuminance relative damage formulae. Then we obtained damage laws to op-TCPs and the lowest color damage spectral power distributions (SPDs) satisfying color quality requirements of a four-primary white LED model. What we achieved can provide theory and application basis for manufacturing white LEDs suitable for illuminating op-TCPs; and the method can be further used in preparing white LEDs applicable to other cultural relics.
... Recently, more and more studies have explored the qualitative influence of visible radiation on paintings, silks, and so on. [29][30][31] However, for our purpose to appraise the damage degree of the four-component LEDs, it is indispensable to quantify the various influences of the corresponding monochromatic lights (450 nm, 510 nm, 583 nm and 650 nm wavebands) on iop-TCPs. ...
DOI:10.1177/1477153518819039
A correlated colour temperature tunable, four-component, LED system suitable for illuminating traditional Chinese paintings painted with inorganic pigments (iop-TCPs) has been designed. This light source can meet the requirements for protective illumination and colour quality in museum illumination. The damage to iop-TCPs caused by the individual 450 nm, 510 nm, 583nm and 650nm monochromatic
LEDs used to construct the LED system were obtained through a longterm illumination experiment. Then, we calculated the damage resulting from the corresponding four-component white LEDs with various spectral power distributions, the intensities of which were iterated by a brute force algorithm. The constructed spectral power distributions were evaluated by the damage and colour quality formulae. The results showed that the better colour quality spectral power distributions with higher correlated colour temperatures cause less damage to iop-TCPs. The lowest damage spectral power distributions, satisfying colour quality requirements with correlated colour temperatures ranging from 2700K to 4000 K, were obtained by calculating the corresponding parameters of the formed spectral power distributions and further selection. This paper not only provides a colour temperature tunable, four-component, white LED system suitable for illuminating iop-TCPs but also sets out a methodology that can be used to identify white LEDs suitable for other cultural relics based on damage limitation and visual requirements.
... The extent of this damage depends on the sensitivity of the exhibited material, the intensity of light and the time of display. High illuminance levels, and long exposure time can accelerate the damage of the exhibited item [13][14][15]. Therefore, if daylight is to be allowed to penetrate into a museum, careful attention must be given to allow just the required amount of light into the space [16,17]. ...
This article investigates how daylight performs in traditional UAE buildings that were turned into museums with specific focus on museum lighting requirements and effect on artefacts. The study used several methods such as on-site measurements, data collection and analysis, and computer simulation. It depended on the climate-based daylighting metric daylighting autonomy. The lighting performance was evaluated throughout the space of a representative model of traditional museum considering the design of the exhibit space and the light sensitivity of traditional artefacts. The results were analysed and design recommendations were presented to improve the overall luminous environment.
... Therefore is important that restorers and optical designers work together. In this task numerical model for aging of paints 24 can be a very useful tool. ...
Since 2019 the authors of this paper were involved in the digital acquisition and storytelling of artifacts belonging museum collections. This work showcases on purpose various related case studies to illustrate key issues in the field. They are the Orcinus Citoniensis paleontological finding (representative of a complex geometry to be acquired), the Annunciation by Beato Angelico (representative of materials with articulate behaviors to light such as the gold foil and tempera), and the Giovanni Battista Amici’s Microscope (representative of non-cooperative specular materials). Since they refer to such different contests, they are a valid test field to bring into the discussion methods and techniques for:
The paper outlines a pipeline from accurate digitization to 3D modeling, texturing, and optimization, culminating in the production of interactive experiences. The aim is the introduction of our experience in authoring high-resolution digital surrogates for scholars and museum visitors, to be explored in museums and cultural institutions through conventional devices or digital interactive kiosks. It emphasizes logistical challenges in photogrammetry for acquiring artifacts, including 3D or 2D objects, paleontological finds, and optically non-cooperating items, with a focus on accurate color acquisition and rendering. The developed pipeline enhances the user experience of 3D digital replicas via visualization apps designed for exhibitions and permanent collections.
When lighting polychrome artworks in museum, the light sources are required not only to provide high-quality visual performance, but also to minimize the photodamage. Currently, though there are mature methods to calculate visual performance, how to predict the degree of photodamage remains a challenge, which leads to a lack of light sources satisfying both visual and protection requirements. Our study conducted a series of 294 accelerated aging experiments spanning over 11 years for materials commonly used in Chinese polychrome artworks, using isoenergetic white-light D 55 and 10 different wavelengths of narrow-band light as experimental light sources. The mathematical model predicting the photodam-age degree caused by intensity (I), exposure time (t), the relative spectral power distribution of the light source (S(λ)), and the irradiated material's relative spectral responsivity (P(λ)) to polychrome artworks was established, and the mean absolute percentage error of the model, as verified by experiments, was 11.63 %. Combined with the existing visual performance calculation methods, an optimal lighting algorithm that simultaneously meets high-quality visual performance and minimum photodamage was developed , followed by developing a new Spectrally Tunable White LEDs (STWLEDs) lighting system with 10 LED chips. It is found that the STWLEDs can adjust and output the optimal spectra and recommended il-luminance according to the characteristics of polychrome artworks, thus realizing lighting with minimum photodamage, meanwhile, satisfying high-quality visual performance. After testing, as well as satisfying the requirements of visual performance, the average photodamage is reduced by 40.95 % with STWLEDs compared with the traditional WLEDs.
W prezentacji przedstawiono charakterystykę technologii oświetlenia typu smart (tzw. inteligentnego) w kontekście zastosowania w przestrzeni muzealnej i dążenia do kompromisu pomiędzy ochroną zbiorów, potrzebą ich udostępniania publiczności i niskim zapotrzebowaniem na energię.
Spectral radiation could cause color damage to dyed cultural relics, and finding a method to obtain a minimum-damage light source is a key issue to be solved. In this paper, the color change behavior of pigments under exposure was experimentally investigated by irradiating 17 typical inorganic pigments used for dyed cultural relics with 10 different narrow-band LED light sources. Through an analysis of the color difference of the test pigments against the amount of exposure, the responsivity equations of the pigments were obtained and a mathematical model for predicting the color damage degree was proposed. The 10 kinds of narrow-band light were combined to obtain 106 LED by using the exhaustive method. The Ra, R9, andDuvvalue of the above spectra were calculated. Ra90, R90, andDuv0.0054 were taken as the evaluation basis, and 35,398 spectra that met color rendering requirements were obtained. The established mathematical model was used to calculate the color damage value to find the minimum-damage spectrum, which was then input into a Thouslite LEDCube system for reduction. An experiment was conducted among the minimum-damage LED and 3 randomly selected light sources, and results showed that the minimum-damage LED light source has an obvious illumination protection effect.
In museum lighting, Chinese paper cultural relics are prone to cracking, embrittlement and other photochemical damage after absorbing the spectral energy of light sources. Owing to the different absorption and reflection characteristics of paper for different bands, optimizing the spectrum compositions of light sources can provide effective protection, the basis of which is to clarify the influence rule of spectra on the paper. However, the methods of color difference and Raman spectroscopy, which are widely used in the current research, cannot scientifically measure the lighting damage. In this study, Fourier transform infrared spectroscopy was used as the evaluation method, and 10 kinds of narrow-band lights were used as the experimental light source to conduct a 1440 h irradiation experiment on the samples of the ancient Chinese Xuan paper. The oxidation index was calculated as the evaluation index based on the infrared spectra measured every 240 hours, and a mathematical model for the response rate of paper to spectrum and exposure was established. 6¹⁰ spectra were obtained with the 10 kinds of narrow-band lights combined and superimposed. The color rendering indexes of the above spectra were calculated, and 9,477 spectra that meet the requirements of viewing indicators were obtained. By calculating the damage degree of the above spectra with the model, the optimal LED spectrum with the minimum damage which met the visual requirements was obtained. Then it was input into the 10-channel spectral simulation system for spectral restoration. Two kinds of lights commonly used in lighting for paper cultural relics were selected to conduct a comparative experiment. The results showed that the optimal LED spectrum reduced damage degree by 49.4% and 59.7% respectively compared with the two kinds of contrast light sources, and was beneficial to energy saving.
Ayasofya, Bizans’ın hayatta kalan en önemli sanatsal bileşenlerini içeren örneklerinden biridir. Kilise, müze ve cami fonksiyonları arasında dönemsel geçişler yaşamasının da etkisiyle farklı dönemlerde çeşitli müdahaleler geçirmiştir ve barındırdığı sanat eserleri bu müdahalelerden etkilenmiştir. 2020’nin Temmuz ayı itibariyle tekrar camiye çevrilmesiyle birlikte toplu ibadet faaliyetleri başlamıştır. Bu fonksiyon değişikliği, mekan içindeki “ibadetin sıhhatini engellemesi” gerekçesiyle, apsis bölümünün üstündeki ikonaların örtülmesini gerekli kılmıştır. Diyanet İşleri Başkanlığı tarafından bu amaca yönelik çeşitli girişimlerde bulunulmuştur. “Karartma” gibi teknikler gündeme getirilse de sonuç olarak hareketli bir perde sistemi ile ikonalar örtülmüş ve bu yaklaşımla yapının iç karakteristiği ve sanatsal bütünlüğü zedelenmiştir. Bu çalışmada bahsi geçen ikonaların ibadet vakitlerinde gizlenmesi için günümüz teknolojisinin imkânları taranmış ve çeşitli alternatifler üzerinden inceleme derinleştirilmiştir. Süslemeleriyle bir bütün olan yapının ana karakteristiğinin korunması hedefiyle yapılan çalışma, özgün bir araştırmayla sonuçlanmıştır.
Hagia Sophia is one of the examples that contain the most important surviving artistic components of Byzantium. It has undergone various interventions in different periods with the effect of periodic transitions between church, museum and mosque functions, and the artworks it contains have been affected by these interventions.
As of July 2020, collective worship activities have started with the conversion into a mosque. This change of function made it necessary to cover the mosaics on the abscissa on the grounds that “it prevents the health of worship” in the space. Various initiatives have been taken by the Directorate of Religious Affairs towards this goal. Although techniques such as “blackout” were brought to the agenda, as a result, the mosaics were covered with a moving curtain system, and with this approach, the interior characteristic and artistic integrity of the building was damaged.
In this study, the possibilities of today's technology to hide the mentioned mosaics during the prayer times were evaluated and it was revealed with the analysis that projection mapping is the technique that best meets this purpose. In addition to the advantages provided by the technique, the possibility of the light emitted to damage the mosaics is one of the areas that the article investigates in terms of protection approaches. This original study, which proceeds with the science of optics as a reference, presents the results obtained by focusing on the mathematics of protecting mosaic works from light.
Ayasofya, Bizans’ın hayatta kalan en önemli sanatsal bileşenlerini içeren örneklerinden biridir. Kilise, müze ve cami fonksiyonları arasında dönemsel geçişler yaşamasının da etkisiyle farklı dönemlerde çeşitli müdahaleler geçirmiştir ve barındırdığı sanat eserleri bu müdahalelerden etkilenmiştir.
2020’nin Temmuz ayı itibariyle tekrar camiye çevrilmesiyle birlikte toplu ibadet faaliyetleri başlamıştır. Bu fonksiyon değişikliği, mekân içindeki “ibadetin sıhhatini engellemesi” gerekçesiyle, apsis bölümünün üstündeki mozaiklerin örtülmesini gerekli kılmıştır. Diyanet İşleri Başkanlığı tarafından bu amaca yönelik çeşitli girişimlerde bulunulmuştur. “Karartma” gibi teknikler gündeme getirilse de sonuç olarak hareketli bir perde sistemi ile mozaikler örtülmüş ve bu yaklaşımla yapının iç karakteristiği ve sanatsal bütünlüğü zedelenmiştir.
Bu çalışmada, bahsi geçen mozaiklerin ibadet vakitlerinde gizlenmesi için günümüz teknolojisinin imkânları taranmış ve projeksiyon haritalamanın bu amacı en iyi karşılayan teknik olduğu analizlerle birlikte ortaya koyulmuştur. Tekniğin sağladığı avantajların yanında yaydığı ışığın mozaiklere zarar verme ihtimali, koruma yaklaşımları açısından makalenin araştırdığı alanlardan biridir. Optik bilimini referans alarak ilerleyen bu özgün çalışma, mozaik eserlerin ışıktan korunmasının matematiğine odaklanarak elde edilen sonuçları sunmaktadır.
A 14th-century manuscript was imaged at high image quality with an HSI detector, using a low-illumination dose of 57 lx h, significantly less than one day’s worth of museum display (≈ 400 lx h). Initial work digitally downsampled spatial resolution from 333 pixels per inch (ppi) to 161 and 80 ppi, and increased the signal-to-noise ratio (SNR) by a factor of 2.00 and 2.79. Despite downsampling, pan-sharpened images were up to 1.5 times spatially sharper than the reference HSI image. Relatively high spectral accuracy was maintained, with spectral angle mapper (SAM) measurements of 0.0527–0.0963. The process was then repeated with physical adjustments to imaging height replacing the digital downsampling process, decreasing resolution from 403 ppi to 111 ppi, increasing SNR from 27.1 to 95.4, and sharpness by 60% using pan-sharpening, while maintaining SAM values of 0.110. An overall image quality metric is proposed, composed of fundamental spatial, spectral, and SNR metrics. This metric highlights efficient lighting and processing methods for increased image quality while limiting total illumination dose on the target, and can be tailored based on one’s imaging constraints.
Spectral and color characterizations reveal aspects of artworks which support the criteria for restoration and subsequent processes. Usually, the aim is to characterize the different compounds and their state in artworks by means of minimally invasive analyses and to provide information on deteriorated areas. It has been applied spectral analysis and other techniques to study the 2011 varnish-removal restoration of Picasso’s Woman in Blue, painted in 1901. Instrumental analyses indicated that the varnish removed in this restoration was an acrylic resin, unavailable at the time Picasso painted this artwork. This varnish acted as a filter absorbing visible light in a selective way (17–24%), modifying the color appearance of the original paint. The painting was characterized spectrally before and after the restoration, indicating that the average color difference for a set of 140 points regularly distributed throughout the painting was 3.8 Commission Internationale de l´Éclairage 1976 L*a*b* units. Specifically, on the average, the restoration substantially increased lightness, slightly decreased chroma, and caused a shift toward less yellow hues. Color changes in two different regions of the painting indicated hue-shifts in different directions. Current measurements will be useful in general conservation processes as a reference to determine future degradation.
The need to achieve energy efficiency standards in the lighting systems of buildings makes it necessary to optimize all aspects of them. Here, the development of a light projection system that achieves this goal by studying and modifying the spectral output, compared to conventional illumination, is described. A lighting system that estimates the reflectance characteristics of artwork and emits optimized lighting can reduce light absorption. A damage-minimizing point-by-point light projection system is developed using an optimization algorithm, to improve the appearance of the surfaces of artworks whose color has faded. In this case, a simulation of an aged oil painting was made by manipulating the original photograph, which was printed and to which the proposed system was applied. The results show that, when the aged printed image is illuminated with the optimized light source, it appears indistinguishable from the non-aged oil painting.
It is possible to assess the damage to artworks by measuring different physical and chemical parameters. One of the most important parameters is colour difference, which is a consequence of chemical changes in the material. CIE 157:2004 ‘Control of Damage to Museum Objects by Optical Radiation’ classifies museum collections into four groups, according to different levels of light fastness. However, these classes were developed from research using traditional light sources. Even though LED technology is becoming more popular, there is no advanced evaluation of colour fading or a colour change test for contemporary artworks. This study established that the CIE 157:2004 method, based on threshold effective radiant exposure, can be applied to an actual ageing test of ultraviolet-blocked light sources including two types of white LEDs and one traditional halogen lamp. The results also present a colour fading model that can be used in museum LED lighting to predict the colour difference in contemporary photographic materials for short- and long-term exhibition. This study also provides a revised light dosage classification of modern photographic materials for museums. Moreover, the verification studies can be used as a conceptual reference for assessing the damage potential of other art materials under the tunable multi-LED system of the future.
Museums have the most demanding lighting criteria among all buildings, due to the sensitivity of stored relics and the need to present and display exhibit them. This article presents the characteristics of intelligent lighting technology in the context of their implementation in a museum building. Its functionalities, and the challenge of maximizing energy efficiency while creating high quality lighting environment, taking into account the stringent requirements of relics preservation, were presented. In this field, the use of intelligent lighting installation creates new possibilities, enabling to reach a compromise at the level unattainable for traditional lighting.
The number of imager devices using multiband or hyperspectral scenes has increased in recent years. For surveillance, or even remote sensing applications, it is necessary to reduce the amount of collected information in order to be useful for automatic or human classification tasks, with affordable performance. In this sense it is very important to filter out only redundant information still preserving the relevant information. In this paper we present an approach in order to compact this information based on a multivariate statistical analysis of spectrums that uses an automatized principal component analysis. Possible applications and use for imagers using color outputs are also given.
Spectral imaging has been widely developed over the last ten years for archiving cultural heritage. It can retrieve spectral reflectance of each scene pixel and provide the possibility to render images for any viewing condition. A new spectral reconstruction method, the matrix R method, can achieve high spectral and colorimetric accuracies simultaneously for a specific viewing condition. Although the matrix R method is very effective, the reconstructed reflectance spectrum is not smooth when compared with in situ spectrophotometry. The goal of this research was to smooth the spectrum and make it more accurate. One possible solution is to identify pigments and find their compositions for each pixel. After that, the reflectance spectrum can be modified based on two-constant Kubelka-Munk theory using the absorption and scattering coefficients of these pigments, weighted by their concentrations. The concentrations were optimized to best fit the spectral reflectance predicted by the matrix R method. As a preliminary experiment, it was assumed that a custom target was painted using several known pigments. The simulation results show that incorporating pigment mapping into the matrix R method can recover the smoothness of the reflectance spectrum, and further improve spectral accuracy of spectral imaging.
The CIELAB lightness and chroma values of pixels in five of the eight ISO SCID natural images were modified to produce sample images. Pairs of images were displayed on a calibrated monitor and assessed by a panel of 12 observers with normal color vision using a categorical judgment method. The experimental results showed that assuming the lightness parametric factor to predict color differences in images, CIELAB performed better than CIEDE2000, CIE94, or CMC, which is a different result to the one found in color-difference literature for homogeneous color pairs. However, observers perceived CIELAB lightness and chroma differences in images in different ways. To fit current experimental data, a specific methodology is proposed to optimize in the color-difference formulas CIELAB, CIEDE2000, CIE94, and CMC. From the standardized residual sum of squares (STRESS) index, it was found that the optimized formulas, CIEDE2000(2.3:1), CIE94(3.0:1), and CMC(3.4:1), performed significantly better than their corresponding original forms with lightness parametric factor . Specifically, CIEDE2000(2.3:1) performed the best, with a satisfactory average STRESS value of 25.8, which is very similar to the 27.5 value that was found from the CIEDE2000(1:1) formula for the combined weighted dataset of homogeneous color samples employed at the development of this formula [J. Opt. Soc. Am. A 25, 1828 (2008), Table 2]. However, fitting our experimental data, none of the four optimized formulas CIELAB(1.5:1), CIEDE2000(2.3:1), CIE94(3.0:1), and CMC(3.4:1) is significantly better than the others. Current results roughly agree with the recent CIE recommendation that color difference in images can be predicted by simply adopting a lightness parametric factor in CIELAB or CIEDE2000 [CIE Publication 199:2011]. It was also found that the different contents of the five images have considerable influence on the performance of the tested color-difference formulas.
A fast, accurate model for computing Logvinenko’s optimal metamers is introduced. The spectral reflectance of an optimal metamer is uniquely determined from a class of metamers with common tristimulus values. A set of optimal metamers is useful for evaluating the color reproduction and gamut of object colors under different illuminants. In conventional methods, optimal metamers are calculated by interpolating the coordinates of precomputed optimal colors. This model optimizes the spectral reflectance parameters efficiently without switching between bandpass (Type I) and bandstop (Type II) optimal metamers, or requiring any stored optimal-color datasets. Some optimal metamer loci computed using MATLAB are presented.
Multiband and hyperspectral imagers are widespread nowadays. Different approaches and technologies are used with this purpose. One of the main problems is to deal with the huge amount of information involved in hyperspectral images. Moreover, in the majority of the cases, the kind of technology used introduces some artifacts into the images. It is necessary to take them into account depending on types of application. In this paper we have applied a multivariate statistical technique known as principal components to characterize different artifacts introduced in hyperspectral imagers. The technique permits to obtain a set of "relevant filters" that could substitute the original system under special conditions.
A colour-difference equation based on CIELAB is developed. It includes not only lightness, chroma, and hue weighting functions, but also an interactive term between chroma and hue differences for improving the performance for blue colours and a scaling factor for CIELAB a* scale for improving the performance for gray colours. Four reliable colour discrimination datasets based upon object colours were accumulated and combined. The equation was tested together with the other advanced CIELAB based equations using the combined dataset and each individual dataset. It outperformed CMC and CIE94 by a large margin, and predicted better than BFD and LCD. The equation has been officially adopted as the new CIE colour-difference equation. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 340–350, 2001
Many works of art have undergone undesirable changes in color since initial creation. The use of spectral or colorimetric imaging, optical models such as Kubelka-Munk turbid-media theory, sample creation using colorants with similar optical behavior to the artist's materials, and color-image processing has enabled the simulation of a work of art before the color change. This paper describes this approach and demonstrates it use on paintings by Vincent Van Gogh and Georges Seurat.
The ultimate goal of spectral imaging is to achieve high spectral accuracy, so that the spectral information can be used to calculate colorimetrically accurate images for any combination of illuminant and observer. A new spectral reconstruction method, called the matrix R method, was developed to reconstruct spectral reflectance factor accurately while simultaneously achieving high colorimetric performance for a defined illuminant and observer. The method combines the benefits of both colorimetric and spectral transformations. Tristimulus values were predicted by a colorimetric transformation from multi-channel camera signals, while spectral reflectance factor was estimated by a spectral transformation from the same signals. The method reconstructed reflectance factor by combining the fundamental stimulus from the predicted tristimulus values with the metameric black from the estimated spectral reflectance, based on the Wyszecki hypothesis. The experimental results verified the new method as a promising technique for building a spectral image database. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 343–351, 2007
In a European multidisciplinary research project concerning environmental diagnostics, museums have been selected, having different climate and pollution conditions, i.e.: Correr Museum, Venice (Italy); Kunsthistorisches Museum, Vienna (Austria); Royal Museum of Fine Arts, Antwerp (Belgium); Sainsbury Centre for Visual Arts, Norwich (UK). Some field tests investigated the microclimate, the gaseous and particulate air pollution and the biological contamination to suggest mitigative techniques that may reduce the potential for damage in the long run. Potential risk factors are generated by imbalance in temperature and humidity, generated by heating, air conditioning or ventilating system (HVAC), or the building structures, exchange of outside air, or large visitor numbers. HVAC may also enhance indoor gaseous pollution. Plants and carpets represent potential niches for bacterial colonisation. Pollutants and particles have been recognised having partly external and partly internal origin. Tourism has a direct negative impact, i.e. transport of external particles, release of heat, vapour and CO2, as well as generation of turbulence, which increases the deposition rate of particulate matter. However, the main problem is that the microclimate has been planned for the well being of visitors during only the visiting time, disregarding the needs of conservation that requires a constant climate by day and by night. In some of these cases, better environmental niches have been obtained with the help of showcases. In other cases, showcases worsened the situation, especially when incandescent lamps were put inside.
Image spectroscopy (IS) is an important tool for the noninvasive analysis of works of art. It generates a wide sequence of multispectral images from which a reflectance spectrum for each imaged point can be recovered. In addition, digital processing techniques can be employed to divide the images into areas of similar spectral behavior. An IS system designed and developed in our laboratory is described. The methodology used to process the acquired data integrates spectral analysis with statistical image processing: in particular, the potential of principal-component analysis applied in this area is investigated. A selection of the results obtained from a sixteenth-century oil-painted panel by Luca Signorelli is also reported.
The use of nuclear technology contributes to the preservation of cultural heritage by assisting the recognition of manufacturing techniques, plus determining the composition of materials and restorations interventions through nuclear analytical techniques for identifying compounds and characterizing the material. Cultural assets affected by biodeterioration agents and the deterioration produced intrinsically and by the environment can benefit from the application of ionizing radiation for disinfestation, disinfection and for consolidation of deteriorated materials.
A method to evaluate the risk of using daylight in museums and cultural heritage exhibitions is presented along this study. Although daylight is an ecological and sustainable source of energy and sometimes also an intrinsic part of the artwork, the use of Natural lighting may cause damages in them due to the difficulty of controlling its variability. The developed method quantifies the damage produced to the artworks by daylight compared to artificial light taking into account the level of radiation and its spectral distribution in space and time by comparison with the damage caused by an Illuminant A (Global Risk Factor). The method, applied to the permanent paintings exhibition in the cloister of the fifteenth century of the Monastery of Santa Maria de El Paular, certifies that the control and exploitation of Natural Light should consider an optimal balance between exposure and damage.
L'article traite de l'éclairage des musées au point de vue de la conservation, en trois parties: (1) Niveau d'eclairage: Comme l'absence des rayons ultraviolets, quoique très nécessaire, n'empêche pas complètement la décoloration il est important d'assurer que la lumière ne soit jamais trop forte. Aujourd'hui on a tendance à éclairer les musées avec des lumières trop puissantes et on devrait combattre cette tendance sans pourtant les rendre tristes et mal éclairés. Le tableau II donne les niveaux d'éclairage maximum recommandés. Pour la plupart des objets, y compris les peintures, le niveau ne doit pas excéder 150 lux. (2) Le déplacement de la radiation ultraviolette: Les matières qui absorbent la radiation ultraviolette sont décrites et recommandées. La référence 13 décrit les expériences qui confirment le pouvoir protecteur des filtres contres les rayons ultraviolets. (3) Le rendu des couleurs: Des tubes fluorescents sont discutés et ceci explique la classification de ces tubes. Les tubes de couleur à basse-température doivent être rejetés.
C'est en 1888 que le Dr Russell et le Capitaine Abney publièrent les résultats d'une série d'expériences très poussées, sur l'influence de la lumière sur les aquarelles. Ils ont exposé des spécimens sur papier Whatman aux rayons solaires et à la lumière diurne, équivalant à au moins 480 ans d'exposition à la lumière du jour dans les galeries de peinture (calcul par les auteurs). Dans la liste suivante figurent les résultats par ordre de stabilité, en commençant par les pigments les plus instables: Carmin fin, laque cramoisie, garance pourpre, laque écarlate, gris de Payne, jaune de Naples, vert olive, indigo, garance brune, gomme-gutte, brun Van Dyck, stil-de-grain, jaune indien, jaune de cadmium, bleu de Leitch, carmin violet, carmin pourpre, sépia, auréolin, garance rose, bleu permanent, bleu d'Anvers, laque de garance, vermillon, vert Véronèse, terre d'ombre brûlée. Les pigments qui ne montrent aucun changement après exposition sont les suivants: ocre jaune, rouge indien, rouge de Venise, terre de Sienne brûlée, jaune de chrome, outremer jaune, terre de Sienne naturelle, terre verte naturelle, oxyde de chrome, bleu de Prusse, bleu de cobalt, bleu d'outremer, cendre d'outremer. Après d'autres expositions à l'air sec, à l'air humide, à l'hydrogène, sous vide, sous verres colorés, etc., Russell et Abney sont arrivés aux conclusions suivantes, choisies parmi plusieurs: la présence d'humidité et d'oxygène est, en général, essentielle pour que s'effectue une altération. Les parties composantes de lumière blanche des bleus et violets produisent les altérations les plus importantes. Le compte rendu se termine en en esquissant quelquesunes des conséquences.
It is frequently assumed that sensitive museum materials follow the reciprocity principle of light exposures. Thus, equivalent exposure doses obtained by using either high-illuminance levels for short periods of time or lower illumination for longer exhibition periods are believed to cause similar degrees of damage to an object. Microfading spectrometry permitted the investigation of this phenomenon by evaluation of light-induced changes in a series of samples. The effects of equivalent exposure doses on materials such as Blue Wool 1, LightCheck Ultra, and various dyed silks from a reference collection were compared. The results indicate that reciprocity is obeyed by the most stable colorants, while materials with lower stability to light may experience deviations that are proportional to the intensity of illumination. This study confirms that reciprocity failure is associated with the use of high-intensity lamps during accelerated-aging trials. Therefore only those tests conducted at low-illumination intensity ranges where reciprocity holds should be employed when one estimates the extent of damage occurring in a museum environment.
Telemaco Signorini (Florence 1835-1901), one of the most important Italian painters of the 19th century, was particularly famous among his colleagues for his way of depicting dark details and shadows by using primarily blue colors. The restoration of his painting Pascolo a Pietramala (c. 1889, Galleria di arte moderna, Palazzo Pitti, Florence) gave the authors the opportunity to study Signorini's blue palette using non-invasive fiber optics reflectance spectroscopy (FORS) in the ultraviolet (UV), visible (vis), and near infrared (NIR) regions (350-1700nm). Furthermore, to help in the identification of the pigments used, a suitable spectroscopic database was created for Prussian blue, artificial ultramarine blue, Thénard blue (or cobalt blue), and cerulean blue modern blue pigments, in masstone and in mixtures with lead white as well as zinc white. The main pigments used by the artist in the aforesaid painting were found to be Prussian blue, artificial ultramarine blue, Thénard blue (or cobalt blue).
Damage to museum objects due to light exposure occurs by two processes: photochemical action and radiant heating effect. The basic physical processes are defined, and the effects of ultraviolet (uv), luminous flux and infrared (IR) exposure on object degradation are examined. Recent research is reviewed, and new data on wavelength dependency of fading lead to some reassessment of attitudes based on earlier data. The aim for lighting and conservation of museum objects is defined as satisfying viewers with the least possible amount of energy being absorbed by the displayed object. Current standards and recommended practices are reviewed, and it is concluded that museum lighting policies should be directed towards control of non-visible irradiance, both IR and uv, and that future research should move beyond examining fading effects of exposure to studying ways to satisfy viewers with minimum absorbed energy.
A procedure to enhance the faded colours of museums artefacts is presented. The method is based on adjusting the spectral profile of the light while maintaining a given white colour of the illumination. The procedure is tested using colour LED clusters and a series of damaged samples and their good condition counterparts. The intensity of the three components of four feasible LED clusters is computed in order to produce white illumination metameric to a white LED light source taken as a reference. Colorimetric calculations are performed to model the colour changes undergone by target colour samples using illumination based on colour LED association with respect to the white LED reference. The model is based on CIELAB specification and allows to optimize the choice of three-colour LED associations that modify the hue and the saturation of a few target colour areas of illuminated samples while other areas are left moderately desaturated. Modelling and experimental visual validation were practically obtained by adjusting the intensity of five calibrated colour LEDs, blue, cyan, green, amber and red, accommodated in a light booth. A visual validation was conducted asking 20 observers to rate the colourfulness appearance of aged inkjet prints under every LED cluster with respect to the colourfulness of their original counterparts under the reference white LED source. The visual assessments agreed with the colorimetric predictions. Finally, a demonstration is shown of the feasibility of the method by simulating the rejuvenated appearance of a natural history specimen of which the museum possesses two differently aged items.
The effect of the wavelength associated with the laser cleaning of polychromes on wood was investigated by using the four harmonics of a Q–switched Nd:YAG laser (1064, 532, 355 and 266 nm). This type of pictorial artwork is very abundant in Spain and substantial effort is directed towards its conservation. Fragments of a XIV century polychrome wooden ceiling of a chapel inside the castle of Mesones de Isuela in Zaragoza were selected for this study. The flat surface of the samples, decorated with red, green, yellow and black paints was covered with dark deposits and polymerised dirt. The modifications induced on the surface of the samples by laser irradiation were studied using optical and vibrational spectroscopies, such as laser-induced fluorescence (LIF), laser-induced breakdown spectroscopy (LIBS) and Fourier-transform Raman (FT-Raman), and infrared (FT-IR). Irradiation in the UV at 266 nm resulted in efficient cleaning of the red (vermilion), green (verdigris) and yellow (orpiment) painted areas. LIF and LIBS spectra showed a relative increase of the pigment features, fluorescence bands and characteristic atomic emissions, respectively, associated with cleaning. Longer wavelengths induced discoloration, although no signs of degradation of pigments or binders were identified. The present work also presents further evidence on how the combined use of the above techniques serves to identify the composition of the paint mixture, including pigments and other inorganic and organic compounds.
During the last decade, the environmental conditions of the museum exhibition facilities and storage areas have been shown to be the most crucial factor, concerning the preservation of collections and artifacts. The pollution (chemicals and noise), the humidity, the temperature and the lighting can possibly deteriorate or even destroy the material cultural goods that are kept, protected and displayed in museum collections. Therefore, the aim of the present report is to define the threats that museum collections may suffer under inappropriate environmental conditions where they are housed.
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