Principles of Color Technology SECOND EDITION

Fred W. Billmeyer, Jr. Professor of Analytical Chemistry Department of Chemistry Rensselaer Polytechnic Institute Troy, New York

Max Saltzman Adjunct Professor of Chemistry Rensselaer Polytechnic Institute and Research Specialist Institute of Geophysics and Planetary Physics University of California, Los Angeles

A Wiley-Interscience Publication

JOHN WILEY & SONS

New York • Chichester • Brisbane • Toronto • Singapore

Contents

Chapter 1 What is Color? 1

A. What This Book Is About 1 B. The Physical Stimulus 2

Sources of Light 3 How Materials Modify Light 8

Transmission 8 Absorption 10 Scattering 11 Other Aspects of Appearance 13 Spectral Characteristics of Materials 13

Detecting Light and Color 15 Summary 17

C. The Description of Color 17 The "Desert Island" Experiment 18 Color Coordinates 19

D. The Appearance of Color 20 Light Sources, Color Rendition, and Chromatic Adaptation 20 Metamerism 21

E. Summary 23

Chapter 2 Describing Color 25

A. Systems Based on Physical Samples 25 Random Arrangements 25 Arrangements Based on Colorant Behavior 26 Arrangements Based on Color-Mixing Laws 26

The Ostwald System 26 Arrangements Based on Steps of Equal Visual Perception 28

The Munsell System 28 The OSA Uniform Color Scales System 30

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The Natural Color System 30 Chroma Cosmos 5000 30

The Universal Color Language 31 B. The CIE System 34

CIE Standard Sources and Illuminants 34 CIE Standard Observers 37

The 1931 CIE Standard Observer 37 The 1964 CIE Supplementary Standard Observer 40

Calculating the CIE Tristimulus Values 44 Chromaticity Coordinates and the Chromaticity Diagram 47 Metamerism 52

C. More Nearly Uniformly Spaced Systems 56 Linear Transformations of the CIE System 57 Opponent-Type Systems 59 Nonlinear Transformations of the CIE System 60

Lightness Scales 60 Uniform Color Spaces 62

One-Dimensional Color Scales 64 Yellowness Scales 65 Other One-Dimensional Color Scales 66 Limitations of One-Dimensional Color Scales 66

Whiteness 66 D. Summary 66

Chapter 3 Color and Color-Difference Measurement 67

A. Basic Principles of Measuring Color 67 Examination 67 Assessment 68 THINK and LOOK 69

B. The Sample 69 Samples for Analysis 69 Form Suitable for Inspection 70 Again, LOOK 71

C. Visual Color Measurement 71 Sample and Single Standard 72 Sample and Multiple Standards 73 Instruments Using the Eye as Detector 75

Disk Colorimetry 75 Color Comparators for Liquids 76 More Refined Instruments 76

D. Instrumental Color Measurement 77 Classification of Methods 77

Unaltered Light 77 Three Colored Lights 77 Monochromatic Light 78

Spectrophotometry 78

Source, Monochromator, and Detector 78 Abridged Spectrophotometry 79

F. G.

Sample Illumination and Viewing 79 Calculation of CIE Coordinates 81 Standardization and Accuracy 82

Colorimetry 85 Source-Detector Response 85 Coordinate Scales 86 Instrument Metamerism 87 Standardization and Differential Use 87

Selecting a Color-Measuring Instrument 89 Features of Current Instruments 90

Speed 90 Reproducibility 90 Computing Power 90 Peripherals 90

Spectrophotometers 90 Diano Hardy II 90 Diano Match-Scan 91 Hunter D54 Series 92 ACS Spectro-Sensor 92 IBM 7409 Series 92

Abridged Spectrophotometers 93 Macbeth 2000 Series 93

Colorimeters 95 Hunter D25 and Gardner XL Series 95 Macbeth 1500 Series 96

Color-Difference Assessment 96 Assessment by Visual Methods 97 Assessment by Instrumental Methods 97

Equations Based on Munsell Data 98 Equations Based on Just-Perceptible-Difference Data Equations Based on the Standard Deviation of Color

Matching 100 The Current CIE Recommendations 101

Perceptibility Versus Acceptability 105 Appropriate Use of Color-Difference Calculations 105 Color Specification and Tolerances 106 Summary 109

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Chapter 4 Colorants 111

A. Some Matters of Terminology B. Dyes Versus Pigments 112

Solubility 113 Chemical Nature 114 Transparency 114 Presence of a Binder 115 Summary 115

C. Classification of Colorants 115

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The Colour Index 115 Special Colorants—Fluorescents and Flakes 118

D. Selecting the Colorants to Use 119 Sources of Information 120

Experienced Personnel 120 Suppliers of Colorants 120 Books and Periodicals 120 The User's Experience 121

General Principles in Choosing Colorants 121 E. Color as an Engineering Material 122

The Various Meanings of Color 122 Engineering Properties of Colorants 124 Color Gamuts 125 The Selection of Colorants 130

F. A Look Ahead 131 G. Summary 132

Chapter 5 The Coloring of Materials in Industry 133

A. Color-Mixing Laws 134 Additive Mixing 134 Simple-Subtractive Mixing 137 Complex-Subtractive Mixing 139

B. Color Matching 141 Types of Matches 141

Invariant Matches 142 Conditional Matches 144

Selection of Colorants 145 Objectives of Color Matching 146 Original Formulations 146 Matching Identical Materials 147 Matching Different Materials 147 Colorant Identification 147 Coordinated Colors 148 Colorant Replacement 149

Strength of Colorants 149 Visual Methods 150 Instrumental Methods—Dyes 150 Instrumental Methods—Pigments 151 Depth of Shade 152

The Initial Match 152 Visual Matching 152 Instrumental Aids 153 Computer-Assisted Formulation 163

Adjusting the Match 167 C. Color Control in Production 168

Monitoring 169 The Value of Instruments 169 The Effect of Process Variables 169 More Than Measurement Alone 169

Adjusting 169 Controlling 171

D. Those Other Aspects of Appearance 172

Chapter 6 Problems and Future Directions in Color Technology 173

A. Unsolved Problems 173 Problems Related to Colorimetry 173

Standard Sources 173 Observer Variability 174 Indices of Metamerism 176 Color-Rendering Indices 177 The Color-Difference Problem 178

Problems Related to Measurements 180 Instrument Agreement 180 Problems of Geometry 182 Special Samples 182

Problems Related to Computer Color Matching 183 Problems with Conventional Samples and Theory 183 Special Samples 185

B. Future Directions 186 The Specification of Color Appearance 186

Subjective (Perceptual) Color Terms 186 Objective Color Terms 187

Chromatic Adaptation 188 Advanced Turbid-Medium Theory 189

C. Educational Opportunities 191 Continuing-Education Courses 192

University Courses 192 Technical Society Courses 192 Manufacturers' Courses 192

Professional Societies 193 The Color Literature 194

D. Back to Principles 194

Chapter 7 Annotated Bibliography 197

A. Books 197 B. Journals and Collected Works 200 C. Color Perception, Description, and Appearance 202 D. Color-Order Systems 203 E. Color Measurement 204 F. Color-Difference Measurement 206 G. Colorants 208 H. Color Matching 209

Bibliography 213 Author Index 231 Subject Index 234

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