Assessing the Impact of LED Lighting on the Stability of Selected Yellow Paint Formulations

Abstract

Light emitting diodes (LEDs) are steadily finding application in an increasing number of museums and heritage institutions, providing energy-efficient solutions for collections display. Although there is a business case to be made for moving toward LED lighting, the safe display of objects must also be ensured. Identifying vulnerable pigments and paints ensures that future preservation strategies will be put in place, avoiding acerbation of damage and reducing the need for conservation. In the first part of our research we investigate color shift and molecular alterations in three yellow paints, namely, lead chromate sulfate, arsenic sulfide, and cadmium sulfide in linseed oil and gum arabic binders. Following an artificial aging regime, color shift was evaluated using colorimetry and molecular alterations were monitored using attenuated total reflectance-Fourier transform infrared spectroscopy coupled with multivariate analysis. Up to 80 Mlux h the lead chromate samples in linseed oil displayed equivalent color shifts approximating 10 ΔE 00 on exposure to the three artificial aging regimes. Color shift has been attributed to the formation of lead oxides evidenced by the appearance of a mid-infrared spectral band at 470 cm −1 assigned to PbO 2. Above 80 Mlux h the formation of lead oxides was exacerbated by exposure to one particular LED. Arsenic sulfide in linseed oil displayed color shifts intensified by both types of LED. Above 40 Mlux h there was a discernible color shift in all samples, with the two LEDs displaying ΔE 00 values two times higher than those displayed by the tungsten halogen samples. The alterations have been attributed to the formation of As 2 O 3 , which is known to form in the presence of wavelengths shorter than 428 nm. Cadmium sulfides in both linseed oil and gum arabic paints did not display discernible color shifts or the presence of degradation products.

New Museum Lighting for People and Paintings

“…In this issue, Richardson et al (2019) delve into the issues underlying the LED lighting movement. They note that, in theory, relighting English Heritage buildings with LEDs might reduce monetary and energy expenditure by 85% compared to the costs of the existing UV-filtered tungsten halogen sources.…”

“…Yet they reiterate the need to ensure that LED relighting will not adversely affect vulnerable pigments, paints, and paper. Given the background of concern over the damage potential of light at 450nm-the emission peak of phosphorbased white-light LEDs- Richardson et al (2019) specifically assessed the impact of such LED lighting on the stability of yellow pigments which are both particularly sensitive to short-wavelength light and also typically used in English Heritage collections. Using an accelerated ageing paradigm, Richardson et al (2019) demonstrate that, in comparison with tungsten halogen lights, two types of LED lighting with short-wavelength power peaks elicit larger colorimetric shifts and chemical degradation in certain pigments.…”

Effects of colored lights on an individual's affective impressions in the observation process

“…As far as the best LED lighting parameters are concerned, research shows that “visibility” and “warmth” (texture) are two factors of perception toward paintings; for the main factor of “visibility,” observers prefer the correlated color temperature (CCT) to be at about 3500K (Zhai et al, 2016 ). Research on the stability of pigments indicates that certain colorants are more vulnerable to degradation when exposed to LED lighting (Richardson et al, 2020 ). In addition, research on visitors' emotional experience shows that upon performing actual tests under gallery conditions, changing the lighting will not make a noticeable difference when there is an opportunity to personally choose the lighting; the average CCT chosen is 3777K (Pelowski et al, 2019 ).…”

The effect of new LED lighting systems on the colour of modern paints

“…Therefore, LED-based lighting systems and their effects on the stability of paint materials used in art still needs to be studied in order to determine if they can be potentially detrimental to the different types of components usually included in a paint system, for example by fast photo-oxidative deterioration. Additionally, although the number of LED ageing studies on paint materials are increased over the last few years [3][4][5][6][7][8][9][10][11][12] , a comprehensive research focused on the investigation of the chemical stability of the irradiated materials is still lacking.Comparison to incandescent light in indoor museums. In comparison to light sources traditionally found in museums such as halogen incandescent lamps, LEDs have a different illumination source, as well as working principles.…”