Hyperspectral Imaging Analyses of Cleaning Tests on Edvard Munch's Monumental Aula Paintings

Cutajar, Jan Dariusz; Deborah, Hilda; Babini, Agnese; Hardeberg, Jon Yngve; Joseph, Edith; Fröysaker, Tine

doi:10.1080/00393630.2022.2054617

Cited by 5 publications

(1 citation statement)

References 11 publications

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“…This allows comprehensive analysis and identification of materials or features based on their distinctive spectral signatures [23]. This assists in identifying hidden details, studying pigments and materials, detecting damages or degradation, and guiding appropriate conservation measures even for rendering such cultural heritage artefacts [7]. However, capturing hyperspectral images is challenging.…”

Section: Introductionmentioning

confidence: 99%

Hyperspectral Imaging of In-Site Stained Glasses: Illumination Variation Compensation Using Two Perpendicular Scans

Kessy,

Funatomi,

Kitano

et al. 2023

2023 IEEE/CVF International Conference on Computer Vision Workshops (ICCVW)

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This paper presents a method for compensating temporal illumination variations in whisk-broom hyperspectral imaging. Whisk-broom imaging scans the scene sequentially, capturing a complete spectrum at each spatial coordinate pixel-by-pixel over time. The scanning process takes time, which is not problematic under constant illumination, but capturing cultural artefacts on-site often involves sunlight as the natural illumination source. While it may be considered beneficial due to its broad spectrum, sunlight fluctuates over time. Thus the resulting hyperspectral image suffers from temporal illumination variation, affecting the observed value and hindering scene analysis. A previous approach proposed using a quick extra single-vertical scan alongside the standard raster (horizontal) scan for compensation. However, it fails when the additional single-vertical scan is performed near or on a black frame. This work aims to overcome this issue by incorporating multiple columns or a full-vertical scan (column scan) to the horizontal scan image (row scan). Furthermore, we introduce a logarithm space and utilise the low-dimensional structures of the illumination and reflectance spectra. Experiments show that the proposed method eliminates the temporal illumination variations in the in-site captured hyperspectral images of stained-glass windows in the historic Amiens Cathedral, France.

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Section: Introductionmentioning

confidence: 99%

Hyperspectral Imaging of In-Site Stained Glasses: Illumination Variation Compensation Using Two Perpendicular Scans

Kessy,

Funatomi,

Kitano

et al. 2023

2023 IEEE/CVF International Conference on Computer Vision Workshops (ICCVW)

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Acquisition strategies for in-situ hyperspectral imaging of stained-glass windows: case studies from the Swiss National Museum

et al. 2023

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Over the last decade, hyperspectral imaging has become a popular technique for the non-invasive identification and mapping of painting materials in many typologies of artworks, thanks to the possibility of obtaining spectral information over the spatial region. A few attempts have also been made on stained-glass windows to identify the chromophore elements responsible for glass color. Hyperspectral imaging of stained glass can be complex; in most cases, stained-glass windows are an integral part of buildings, and sunlight represents the natural light source for illuminating these artifacts. While it may be considered an advantage, sunlight is not homogeneous throughout the day, and different weather conditions can affect the quality of the hyperspectral images. In addition, the presence of buildings and vegetation in the background could also modify the colors of the stained-glass windows and consequently alter the characteristic peaks of the chromophores in the spectra. This work aims to solve some of these issues and proposes different strategies to improve the results obtainable in situ. The methodology was tested on stained-glass panels displayed in the windows of the Swiss National Museum. Stained-glass panels located in windows of an internal wall were also analyzed, developing a lighting setup to account for the lack of natural light. Hyperspectral images of the selected stained glass were acquired multiple times, choosing different transmittance references for the preprocessing and exposure time to evaluate differences in the collected spectral images. The use of a diffuser sheet to mitigate the effect of external factors was also tested on some panels exposed to sunlight. Results from representative case studies will be presented to discuss the feasibility and limitations of in-situ hyperspectral imaging applications on stained glass and provide some general recommendations to consider during the acquisitions.

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The role of SVOCs in the initial film formation and soiling of unvarnished paintings

Grøntoft,

Cutajar

2023

Herit Sci

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In recent years increased research efforts and environmental improvements have been directed towards the preventive conservation of the monumental, unvarnished oil paintings on canvas (1909–1916) by Edvard Munch (1863–1944) housed in the University of Oslo Aula. Surface soiling of the paintings has been a documented issue since their display, and the modern-day effect of air-borne particulates and gases on the painting surfaces remains hitherto undocumented. For the first time in the Aula, this study has measured the in-situ time-dependent mass deposit of air pollution onto vertical surfaces over the period of one year (2021–2022). Concomitant measurements of the concentrations of ozone (O3) and nitrogen dioxide (NO2) were also taken, to complement periodic data from 2020. The mass deposit was measured through incremental weight changes of Teflon membrane filters, and quartz filters for analysis of elemental/organic carbon (EC/OC), whilst the gaseous pollutants were measured using passive gas samplers. Indoor-to-outdoor ratios (I/O) for O3 were noted to be higher than those suggested by earlier data, whereas NO2 I/O ratios were found to be lower, indicating a stronger oxidising atmosphere in the Aula. Just over half of the deposited mass on the quartz filters was found to be OC, with no EC detected. Surprisingly, an overall decrease in the mass deposit from three to twelve months was measured on the Teflon membrane filters. It was hypothesised, based on models reported in the literature, that the source of the OC on the filters was mainly gaseous, semi-volatile organic compounds (SVOCs), which were present in an adsorption/desorption equilibrium that was dependent on possible SVOC emission episodes, relative humidity levels, gaseous oxidative reactions and the particulate matter deposit. A simple mathematical model is proposed to rationalise the observed mass deposits on the filters, together with a discussion of uncertainties affecting the measurements. The hypothesis preliminarily indicates the possible and previously unconsidered role of SVOCs on the initial film formation of soiling layers on the Aula paintings, and could bear implications for their monitoring in the preventive care of unvarnished oil paintings on canvas.

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Hyperspectral Imaging Analyses of Cleaning Tests on Edvard Munch's Monumental Aula Paintings

Cited by 5 publications

References 11 publications

Hyperspectral Imaging of In-Site Stained Glasses: Illumination Variation Compensation Using Two Perpendicular Scans

Hyperspectral Imaging of In-Site Stained Glasses: Illumination Variation Compensation Using Two Perpendicular Scans

Acquisition strategies for in-situ hyperspectral imaging of stained-glass windows: case studies from the Swiss National Museum

The role of SVOCs in the initial film formation and soiling of unvarnished paintings

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