A Multi-Analytical Approach for Studying the Effect of New LED Lighting Systems on Modern Paints: Chemical Stability Investigations.

Valentina Pintus,Christoph Haisch,Marta Anghelone,Katja Sterflinger,Ferenc Szabó,Karin Wieland,Manfred Schreiner,Péter Csuti,Ottavia Santorelli,Carlotta Salvadori,Dávid Noel Tóth

doi:10.3390/polym13244441

Abstract

This study aims to investigate the chemical stability of some modern paint samples exposed to a new Light Emitting Diode (LED)-lighting system and a halogen lamp by using micro-attenuated total reflectance of Fourier transform infrared spectroscopy (µ-ATR-FTIR), µ-Raman, pyrolysis—gas chromatography/mass spectrometry (Py-GC/MS), and thermally assisted hydrolysis and methylation of GC/MS (THM-GC/MS). Those investigations were performed before and after the exposure of the samples to lightings for 1250, 2400, 3300, and 5000 h. The results obtained with µ-Raman spectroscopy show the high stability of the selected inorganic pigments after the exposure to the lighting systems; while similar to the UV/Vis/NIR results reported in a previous study, µ-ATR-FTIR and THM-GC/MS results evidence greater chemical changes occurring principally on the linseed oil binder-based mock-ups among the acrylic and alkyd-based samples. Moreover, principal component analyses (PCA) and hierarchical cluster analyses (HCA) of THM-GC/MS results highlight that those changes were mostly dependent on the exposure time and on the type of pigment, while being independent of the lighting system used. Finally, semi-quantitative µ-ATR-FTIR results show slight pigment enrichment at the paint surface due to the auto and photo-oxidative degradation of the linseed oil binder.

Highlights

Paint colours used in modern-contemporary art and found in indoor museum collections are widely represented by paints using acrylic, alkyd, and oil as binding media
This study aims to investigate the chemical stability of some modern paint samples exposed to a new Light Emitting Diode (LED)-lighting system and a halogen lamp by using microattenuated total reflectance of Fourier transform infrared spectroscopy (μ-ATR-FTIR), μ-Raman, pyrolysis—gas chromatography/mass spectrometry (Py-GC/MS), and thermally assisted hydrolysis and methylation of GC/MS (THM-GC/MS)
In order to gain a precise picture about the influence of the illuminants on the samples and to reveal the role played by each variable in the experiments—e.g., ageing time, binder, pigment–binder combination, and lighting system—principal component analyses (PCA) of the Py-GC/MS and THM-GC/MS data were performed

Summary

Introduction

Paint colours used in modern-contemporary art and found in indoor museum collections are widely represented by paints using acrylic, alkyd, and oil as binding media. The light from lighting systems represents the main parameter of concern in indoor museums, along with temperature and relative humidity. Modern light sources such as light emitting diode (LED)-based ones can be found nowadays in an increasing number of museums, due to their high luminous efficiency, long lifetime, and reliability. Their most important advantage is that they emit no radiation in the damaging spectral ranges (UV and infrared). LEDs are being increasingly used in indoor museums and guidelines regarding their implementation selection are still developing [1,2], the long-term effects of their emitted light on modern paints are not yet well known

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