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The Effects of Finish Coatings on Ultraviolet and Visible Light Stability of Inkjet Prints MA Thesis

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The Effects of Finish Coatings on Ultraviolet and Visible Light Stability of Inkjet Prints MA Thesis The effects of finish coatings on ultraviolet and visible light stability of inkjet prints MA thesis Student: Ella Solomon Student number: 11596139 Supervisor: Katrin Pietsch Programme: Conservation and Restoration of Cultural Heritage, [Photography] Date: July 2020 Acknowledgments I would like to express my appreciation to the many professionals who have helped me along the way. First, I would like to thank Katrin Pietsch, my course coordinator and thesis supervisor at the University of Amsterdam (UvA), for her constructive guidance and patience through the entire process. Next, I would like to sincerely thank Dr René Peschar at UvA who kindly supported the challenge of understanding the characteristics and photodegradation of polymers in light of the experimental results. A special thanks goes out to Clara von Waldthausen, Prof. Dr Maarten van Bommel, Prof. Dr Ella Hendriks and Dr Maartje Stols-Witlox at UvA for overseeing the general research process, providing guidance and sharing their insights. Colour measurements would not have been possible without the patient explanations by Dr Emilie Froment and Kate van Lookeren Campagne at UvA on performing the measurements. This research study was made possible by Ryan Boatright, the co-founder of the printing and conservation studio Atelier Boba, who brought up the idea for this research study and created the samples for the experiment in his Paris studio. The experimental part of the study would not have been possible without the generosity of Drs Agnes Brokerhof, senior scientist at the Rijksdienst voor het Cultureel Erfgoed (RCE), who helped me through the entire process and introduced me to the concept of artificial weathering. A special thanks goes out to ing. Saskia Smulders, MA, PD res. and Henk van Keulen, RCE, who performed and analysed the coatings materials during the turbulent times of the COVID-19 pandemic. I am also thankful to Dr Bill Wei, Drs Frank Ligterink and Dr Han Neevel who shared their knowledge and offered input on the solar spectrum and colour measurements. Lastly, I would like to thank my classmates for sharing their experiences, especially Tessa Maillette De Buy Wenniger who was a great help in the practical experiment in the days of the COVID-19 outbreak and was willing to answer any chemistry-related questions. A final thanks is due my family and friends in my home country for their long-distance support and to my friends from the Netherlands who offered their kind expert assistance. The effects of finish coatings on ultraviolet and visible light stability of inkjet prints Master’s Thesis Ella Solomon (11596139) University of Amsterdam, July 2020 Light stability of finish coatings and their effect on inkjet prints in terms of colour change is discussed. The coatings’ material content was analysed using gas chromatography mass spectrometry (GC-MS). The coatings were applied on unprinted and printed samples of Fine Art paper and put in Xenontest for overall 121 mega lux hours. The samples were then compared using L*a*b colour space. The chemical reactions causing colour change are complex due to the various materials involved. Dit werk bespreekt de lichtstabiliteit van verschillende coatings en hun effect op inkjetprints wat betreft kleurverandering. De bestanddelen van de zes coatings zijn geanalyseerd met gaschromatografie massaspectrometrie (GC-MS). De coatings zijn toegepast op onbedrukte en bedrukte monsters kunstenaarspapier en gedurende in totaal 121 megalux uur aan een Xenontest onderworpen. De kleurverandering van de monsters is gemeten aan de hand van het L*a*b kleurenmodel. De chemische reacties die kleurverandering veroorzaken zijn complex vanwege de diverse betrokken materialen. Table of Contents Introduction ..................................................................................................................................... 1 1. Fundamentals .............................................................................................................................. 2 1.1. History and technology of inkjet .......................................................................................... 2 1.1.1 The inkjet print ............................................................................................................... 2 1.1.2. Component materials of the inkjet print: inks and media .............................................. 3 1.1.3. Finish coatings for inkjet prints ..................................................................................... 4 1.2. Research Material Focus ...................................................................................................... 5 1.2.1. Epson UltraChrome Pro inks and Hahnemühle Photo Rag® fine art paper.................. 5 1.2.2. Hahnemühle, Rauch and Breathing Color finish coatings ............................................ 6 1.3. Research Objective ............................................................................................................... 6 1.4. Current Scientific Knowledge .............................................................................................. 7 2. Polymer Binders and Light Stabilisers in Finish Coatings ....................................................... 11 2.1. Characteristics .................................................................................................................... 11 2.1.1. Polyethylene glycol-polyvinyl alcohol ........................................................................ 11 2.1.2. Polyurethanes............................................................................................................... 14 2.1.3. Polyacrylates ................................................................................................................ 16 2.1.4. Photostabilising additives in coatings.......................................................................... 17 2.2. Photodegradation pathways of polymer binders ................................................................ 20 2.2.1. Polyethylene glycol-polyvinyl alcohol ........................................................................ 22 2.2.2. Polyester urethanes ...................................................................................................... 24 2.2.3. Polyacrylates ................................................................................................................ 27 2.2.4. Incorporation of light stabilisers and their effect on polymer binders ........................ 30 2.3. Discussion: the ageing behaviour of weathered finish coatings on inkjet prints ............... 31 3. Methodology ............................................................................................................................. 34 3.1. Questionnaires and correspondences: manufacturers, conservators and scientists ............ 34 3.2. Experimental ...................................................................................................................... 36 3.2.1. Sample creation ........................................................................................................... 36 3.2.2. Material analysis using gas chromatography mass spectrometry ................................ 39 3.2.3. Artificial UV and light ageing using Xenontest .......................................................... 39 3.2.4. Colour measurements .................................................................................................. 41 4. Results and Discussion ............................................................................................................. 43 4.1. Material Analysis (THM-GCMS) ...................................................................................... 43 4.2 Colour Measurements ......................................................................................................... 43 4.3. Discussion .......................................................................................................................... 49 5. Conclusions ............................................................................................................................... 54 Summary ....................................................................................................................................... 57 Bibliography ................................................................................................................................. 59 Appendices .................................................................................................................................... 64 The effects of finish coatings on ultraviolet and visible light stability of inkjet prints Introduction Inkjet printing is a common practice in digital photography and is employed by contemporary artists and by the general public in day-to-day life in the office or at home. In addition to the technological developments of inkjet printing, products such as finish coatings were marketed to achieve long-lasting durability. This document will discuss the photostability qualities of six inkjet finish coatings and their effect on Epson UltraChrome Pro inks and Hahnemühle Photo Rag® fine art paper typically employed by printing studios and photographers worldwide for their aesthetic and durable characteristics. Despite the inert lightfastness provide by the inks and paper, inkjet prints are still prone to deterioration and discolouration when exposed to light and ultraviolet (UV) radiation. Although finish coatings have been created to improve the
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