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Introduction
Light is one of the most persistent and paradoxical agents of deterioration in preventive conservation. It is essential for the display and interpretation of cultural heritage, yet it can cause irreversible damage to many materials. Unlike agents such as fire or water, light acts gradually, generating cumulative physical and chemical changes with each exposure.
The management of light in museums, therefore, involves a fundamental ethical dilemma often described as “see versus save.” As Michalski states, “objects need light to be seen, but light damages them” (Michalski 2016, 2). Museums must balance access with preservation, recognizing that light damage is cumulative and irreversible, with no true recovery from fading or material degradation, as even low light levels, such as 50 lux—established as a benchmark for visibility—still contribute to cumulative damage (CCI 2014).
This paper evaluates the accuracy and completeness of the video clip by Todd da Silva (2020) by comparing it with professional literature, particularly Risk Management for Collections (Brokerhof, Ankersmit, and Ligterink 2017). The aim is not to compare sources with each other, but to assess how effectively the video reflects established knowledge.
The research question is: How realistic and complete is the information about light as an agent of deterioration presented in the video compared to professional sources?
This evaluation is informed by the RCE risk management framework, including the scenario scheme and the strategies of avoid, block, and detect. The sources are analyzed thematically to evaluate different aspects of light as an agent of deterioration.
Sources
Ashley-Smith, Jonathan, Alan Derbyshire, and Boris Pretzel. 2002. “The Continuing Development of a Practical Lighting Policy for Works of Art on Paper and Other Object Types at the Victoria and Albert Museum.” In Preprints of the 13th ICOM-CC Triennial Meeting Rio de Janeiro, Vol. 1, 3–8. London: ICOM-CC.
Ashley-Smith, Derbyshire, and Pretzel (2002) are conservation professionals at the Victoria and Albert Museum (V&A). Their work is highly reliable, as it is based on institutional practice and long-term policy implementation.
The article presents a structured lighting policy based on classifying objects according to their light sensitivity (vulnerable, sensitive, durable, permanent) (Ashley-Smith et al. 2002, 1). It introduces the concept of perceptible change, defined as approximately ΔE00 = 1.5, and proposes limiting damage to
“one perceptible change (ΔE00 = 1.5) in 50 years” (Ashley-Smith et al. 2002, 5). This approach prioritizes long-term preservation and the control of cumulative exposure, emphasizing the need to preserve collections for future generations. This concept relates to the idea of just noticeable change (JNC), which defines the threshold at which color differences become perceptible to the human eye (Ashley-Smith et al. 2002, 5).
From a risk management perspective, these measures correspond to avoidance strategies , as they aim to reduce exposure over time, including rotation and restricted display durations (Ashley-Smith et al. 2002, 7). They also reflect a structured approach consistent with the RCE scenario scheme, in which damage is anticipated and controlled through defined limits.
This source confirms general principles such as reducing light levels and limiting exposure time, for example, to no more than 20% of the display period (Ashley-Smith et al. 2002, 6). However, it also reveals that the clip is reduced, as it does not consider exposure quotas or display limits such as those defined in museum lighting policies (Ashley-Smith et al. 2002, 6), nor does it address the trade-off between visibility and preservation, where higher light levels improve perception but significantly increase damage (CCI 2014).
Michalski, Stefan. 2016. Agents of Deterioration: Light, Ultraviolet, and Infrared****. Ottawa: Canadian Conservation Institute.
Michalski (2016) provides a key theoretical framework for understanding light as an agent of deterioration. He distinguishes between ultraviolet (UV), visible light, and infrared (IR), explaining that “ultraviolet radiation causes yellowing… and/or disintegration,” while visible light causes fading and IR contributes to heat (Michalski 2016).
A central concept is cumulative exposure, expressed in lux hours, demonstrating that damage depends on both light intensity and duration. This dose-based approach allows deterioration to be measured and controlled, even though relatively low levels such as 50 lux are sufficient for visual perception (CCI 2014). Michalski also highlights the interaction between IR, temperature, and relative humidity, which accelerates degradation processes through increased temperature and changes in relative humidity—an aspect not addressed in the video.
From a risk management perspective, light is controlled through avoid, block, and detect strategies , such as reducing exposure, filtering UV radiation, and monitoring light levels. These measures reflect a structured approach consistent with the RCE scenario scheme , where risks are assessed and mitigated systematically.
risks for light-sensitive materials and have not been proven safe (Druzik and Michalski 2011). This shows that LED safety depends on spectral characteristics.
From a risk management perspective, this supports the need for precise block strategies , where harmful wavelengths are carefully controlled through detailed analysis of spectral power distribution.
Compared to the video, this source both supports and refines its claims. While the clip presents LEDs as generally safe, it oversimplifies the issue by treating them as inherently safe. In contrast, professional practice requires detailed technical evaluation of lighting systems, highlighting a level of complexity that is not addressed in the video.
Ford, Bruce, and Nicola Smith. 2011. “Lighting Guidelines and the Lightfastness of Australian Indigenous Objects at the National Museum of Australia.” In Preprints of the 16th Triennial Conference, ICOM-CC, Lisbon****.
Ford and Smith (2011) provide a relevant case study on assessing light sensitivity in museum collections. Their work focuses on the use of microfade testing to evaluate object-specific lightfastness.
The study tested over 200 objects using a microfade tester, which measures color change through a concentrated light beam and compares results with Blue Wool standards. Notably, around 50% of the objects were found to be more stable than expected (Ford and Smith 2011). This demonstrates that general sensitivity categories may not always reflect actual material behavior.
This method supports evidence-based conservation, allowing museums to move beyond assumptions and develop tailored exhibition strategies. From a risk management perspective, it strengthens detection strategies , as it enables precise measurement of material sensitivity and supports informed decision-making.
Compared to the video, this source highlights a key limitation. While the clip explains light damage in general terms, it does not address how sensitivity is assessed in practice. The absence of object-specific evaluation methods results in a more simplified representation, lacking the precision required in professional preventive conservation.
Canadian Conservation Institute. 2014. Light Damage Calculator. http://canada.pch.gc.ca/eng/
The Canadian Conservation Institute (CCI) provides the Light Damage Calculator, a professional tool used to model cumulative light exposure and predict fading. Although not a traditional academic publication, it is highly reliable and widely used in practice.
The tool is based on the concept of cumulative exposure, expressed in lux hours, where damage depends on both light intensity and duration. It allows users to estimate colour change (ΔE) and visualize the effects of different lighting conditions over time. This makes abstract concepts such as fading measurable and supports data-driven decision-making.
From a risk management perspective, the calculator enables conservators to compare different exposure scenarios within a scenario scheme , supporting informed decisions across avoid, block, and detect strategies. It demonstrates that light management involves prediction, modeling, and quantification rather than simple rules of thumb.
These sources both support and extend its claims. While the clip correctly explains that light damage is cumulative, it does not introduce analytical tools or predictive methods. As a result, it provides a superficial explanation that lacks the quantitative and scenario-based approach central to contemporary preventive conservation practice.
Padfield, Joseph. 2015. “Spectral Power Distribution (SPD) Curves.” The National Gallery, London
Padfield (2015), a scientist at the National Gallery, provides a technical resource on spectral power distribution (SPD) for analysing light sources in museum contexts. Although not a traditional academic text, it is highly reliable due to its institutional basis.
The main contribution of this work is to demonstrate that light cannot be adequately assessed through lux alone. Lux measures perceived brightness but does not account for spectral composition. As Padfield shows, two lamps with similar lux levels can have very different wavelength distributions, leading to variations in colour rendering and risk.
This highlights the importance of evaluating the quality and distribution of wavelengths, as different parts of the spectrum affect materials differently. From a risk management perspective, this is essential for effective block strategies , which rely on controlling harmful wavelengths rather than only reducing light intensity.
This text reveals a significant simplification. While the clip focuses on limiting light levels, it does not address spectral composition or its impact on deterioration. As a result, it overlooks a key factor in professional light management and limits the effectiveness of risk control strategies.
Overall, the video lacks a consistent application of the RCE framework, as it does not fully integrate the scenario scheme or systematically apply to avoid, block, and detect strategies.
Conclusion
Druzik, James R., and Stefan Michalski. 2011. A User’s Guide for Selecting Solid-State Lighting for Museum Use. Los Angeles and Ottawa: Getty Conservation Institute and Canadian Conservation Institute.
Ford, Bruce, and Nicola Smith. 2011. “Lighting Guidelines and the Lightfastness of Australian Indigenous Objects at the National Museum of Australia.” In ICOM Committee for Conservation, 16th Triennial Conference, Lisbon: Preprints.
Michalski, Stefan. 2016. Agents of Deterioration: Light, Ultraviolet, and Infrared. Ottawa: Canadian Conservation Institute.
Padfield, Joseph. The National Gallery Spectral Power Distribution (SPD) Curves. London: The National Gallery. http://research.ng-london.org.uk/scientific/spd/?page=home.
Saunders, David, and Jo Kirby. 2008. “A Comparison of Light-Induced Damage under Common Museum Illuminants.” In ICOM Committee for Conservation, 15th Triennial Meeting, New Delhi: Preprints , vol. 2, 766–774.
da Silva, Todd. 2020. Light Damage in Museums [video].
