Hochschularbeit

Ruaidhrí O´Bolguidhir: Wood and Light: An examination of colour alteration due to exposure to light of the Hildesheim wood tablet collection and discussion of a method of monitoring colour change through the possibilities of digital photography Zurück
Sprache: Original   -   Übersetzung
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Zusammenfassung: The exposure to light is an ever-present threat to historic objects composed of organic materials. In the case of wooden objects, this exposure can lead to surface colour alteration. Most examinations on this subject are based on experimentation under artificial conditions. In this study, an attempt was made to analyse wood surface discolouration due to indoor light (sunlight through window glass) under real life conditions, based on digital photographs of the Hildesheim wood tablet collection. The sample group consists of 92 wooden tablets of four wood types, which have been exposed to light over a five to fifteen year period. Colour measurements were performed on the digital photographs, by means of the graphics editing program, Adobe® Photoshop® CS. These measurements provide an idea of the different behaviour of the four woods under light exposure and over this time frame. The results were compared with a previous examination of the tablets which had been done visually and were also compared with relevant recent literature.

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Schlagworte: light wood colour
Inhalt: 1 Introduction 1
1.1 Starting point and motivation 1
1.2 Structure of the work 1

I – Theoretical Part 2
2 Light 3
2.1 What is light? 3
2.1.1 Measuring light 4
2.1 Light as threat to objects 6
2.1.1 Risk 7
2.1.2 Reciprocity 9
2.1.3 Reducing damage 10

3 Colour 13
3.1 What is colour? 13
3.2 Defining a colour 16
3.2.1 RGB 19
3.2.2 CIE L*a*b* system 21

4 Wood 27
4.1 The colour of wood 27

5 Wood and Light 35
5.1 The susceptibility of wood to light 36
5.2 What is the cause? UV versus Visible light 38
5.3 What are the effects? 42
5.3.1 Chemical change 42
5.3.2 Colour alteration 45
5.3.3 Other changes associated with light exposure 50
5.4 Summary of the theoretical research 51

II – Practical Part 52
6 Material and Method 53
6.1 Objects and material 53
6.1.1 The Hildesheim wood tablet collection 53
6.1.2 The Letterfrack wood samples 54
6.2 Assessment of the tablets by visual examination 56
6.2.1 Problems encountered during visual examination 56
6.3 Thought process 60
6.4 Developing the method 63
6.5 Refining the method 66
6.5.1 Testing the methods 66
6.6 The examination 71
6.6.1 Hildesheim wood tablets under visible light 71
6.6.2 Hildesheim wood tablets under ultraviolet light 74
6.6.3 Letterfrack wood samples 75

7 Results 76
7.1 Hildesheim wood tablet under visible light 76
7.1.1 The walnut samples 81
7.1.2 The mahogany samples 84
7.1.3 The oak samples 87
7.1.4 The maple samples 90
7.2 The Hildesheim wood tablets under ultraviolet light 93
7.3 The Letterfrack samples 99
7.4 Comparison of the examination of the photographs with the visual examination 101
7.5 Comparison of the results based on the Hildesheim wood collection with other work in this field 105

8 Discussion 112
8.1.1 Evaluation of the results 112
8.1.2 Evaluation of the testing method 113
8.1.3 Suggestions for further action 116

9 Conclusion 118
Bibliography 120
Table of figures 120
List of tables 123
List of sources 124

Appendix 128

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weitere Angaben:
  • Hochschule:  HAWK Hochschule für angewandte Wissenschaft und Kunst Hildesheim/ Holzminden/Göttingen
  • Art der Arbeit:  Masterarbeit
  • Erstprüfer:  Prof. Dr. Gerdi Maierbacher-Legl
  • Zweitprüfer:  Hon.-Prof. Dr. Peter Klein
  • Abgabedatum:  2010
  • Sprache:  English
  • Seitenzahl:  119
  • Abbildungen:  86
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