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                       LIGHT AND COLOUR THEORIES

[Illustration: TINTOMETER. Form of Instrument for Opaque Observation.]




[Illustration: Reproductions of some Medals awarded to JOSEPH W. LOVIBOND’S
Method of Colour Analysis FOR Scientific and Commercial Purposes.]




                               LIGHT AND
                            COLOUR THEORIES

                    and their Relation to Light and
                        Colour Standardization

                                  By

                          JOSEPH W. LOVIBOND

               ILLUSTRATED BY 11 PLATES  BY HAND

[Illustration: Logo]

                                London

            E. & F. N. SPON, Limited, 57 HAYMARKET

                               New York

                SPON & CHAMBERLAIN, 123 LIBERTY STREET

                                 1915




CONTENTS


                                                             PAGE

  List of Plates                                              vii

  Purpose                                                      ix


                          CHAPTER I.
  Introduction                                                  1


                          CHAPTER II.
  Evolution of the Method                                       5


                          CHAPTER III.
  Evolution of the Unit                                         9


                          CHAPTER IV.
  Derivation of Colour from White Light                        11


                          CHAPTER V.
  Standard White Light                                         14


                          CHAPTER VI.
  Qualitative Colour Nomenclature                              17


                          CHAPTER VII.
  Quantitative Colour Nomenclature

                          CHAPTER VIII.
  The Colour Scales                                            28


                          CHAPTER IX.
  Colour Charts                                                31


                          CHAPTER X.
  Representations of Colour in Space of Three Dimensions       34


                          CHAPTER XI.
  The Spectrum in relation to Colour Standardization           36


                          CHAPTER XII.
  The Physiological Light Unit                                 45


                          APPENDIX I.
  Colour Education                                             59


                          APPENDIX II.
  The Possibilities of a Standard Light and Colour Unit        69

                          APPENDIX III.
  Dr. Dudley Corbett’s Radiometer                              83


  Index                                                        89




ERRATA.


    Plate I. Newton’s Theory. The Indigo line is erroneously placed
    between the Violet and the Red; it should be between the Blue
    and the Violet.

    Page 40.--_Fifth line from the bottom, for_ Fraunhoper _read_
    Fraunhofer.


_To face p. vi., Lovibond, Light and Colour Theories._] [P.R. 1317




LIST OF PLATES


                                                           TO FACE
                                                             PAGE

  Plate  I. Six Colour Theories                                 4

    "   II. Circles Illustrating Absorption of White Light     11

    "  III. Diagram Illustrating Analysis of White Light       13

    "   IV. First System of Charting Colour                    31

    "    V. Second System of Charting Colour                   33

    "   VI. Six Tintometrical Colour Charts                    39

    "  VII. Two Circles                                        40

    " VIII. Absorption Curves of Dyes                          76

    "   IX. Fading Curves of Dyes                              78

    "    X. Comparison Curves of Healthy and Diseased Blood    80

    "   XI. Specific Colour Curves of Healthy and Diseased
            Human Blood                                        82




PURPOSE


The purpose of this work is to demonstrate that colour is a
determinable property of matter, and to make generally known methods
of colour analysis and synthesis which have proved of great practical
value in establishing standards of purity in some industries.

The purpose is also to show that the methods are thoroughly scientific
in theory and practice, and that the results are not likely to be
changed by further discoveries. Also that out of the work done a new
law has been developed, which the writer calls the Law of Specific
Colour Development, meaning that every substance has its own rate of
colour development for regularly increasing thicknesses.


THE THEORY.

Of the six colours in white light--red, orange, yellow, green, blue
and violet; Red, Yellow and Blue are regarded as dominants, because
they visually hold the associated colours orange, green and violet in
subjection.

An equivalent unit of pure red, pure yellow and pure blue is adopted,
and incorporated into glass. The unit is multiplied to obtain greater
intensities, and divided to obtain lesser intensities.

The  glasses are called absorbents. The red absorbent transmits
violet, red and orange, but the red ray alone is visible as colour,
until the other absorbents are superimposed, and the character of the
group of rays changed. In the same way yellow transmits orange and
green, and blue transmits green and violet, whilst the yellow and blue
alone are visible as colour. Orange, green and violet are here called
subordinates, which may be developed as follows:--

    Or. = R. + Y.   Gr. = Y. + B.   Vi. = B. + R.

Twenty-five years’ experience in the application of the theory and the
method to the requirements of practical work, have given no reason for
change. Following will be found a list of awards from International
Juries and Scientific Societies, also a list of industries in which the
writer’s method is giving entire satisfaction.


Awards by International Juries.

  St. Louis                1 Silver Medal.
                           2 Bronze Medals.

  Brussels                 1 Gold Medal.
                           3 Silver Medals.

  Turin                    Diploma of Honour.
                           1 Gold Medal.
                           1 Silver Medal.


Awards by Scientific Societies.

  Sanitary Institute of Great Britain--
      _Bronze_ Medal for Colourometrical Water Analysis.

  Royal Sanitary Institute--
      _Bronze_ Medal for Measuring Smoke Densities.

  International Congress on School Hygiene--
      _Bronze_ Medal for Colour Educator.

  Royal Sanitary Institute--
      _Silver_ Medal for Colour Educator.

  Smoke Abatement Society, Sheffield--
      _Diploma_ for System of Colour Measurement.

  Royal Sanitary Institute--
      _Bronze_ Medal for Quantitative Estimation of Colour Blindness.

  Franco-British Exhibition--
      _Gold_ Medal for Colour Educator.

  International Medical Congress--
      _Bronze_ Medal for Tintometer as Medical requisite.

  Royal Sanitary Institute--
      _Silver_ Medal for recent developments.

  Royal Sanitary Institute--
      _Silver_ Medal Corbett’s Radiometer.

Formal Adoption of Tintometer Standards by--

  The Petroleum Industry.
  The Massachusetts Board of Health.
  The International Association of Leather Trades Chemists.
  The Inter-states Cotton Seed Oil Association.
  The Bureau of Engraving and Printing, China.

In general use by the following Industries--

  Brewing and Malting.
  Tanning.
  Wine and Spirit Merchants.
  Dyeing and Printing.
  Paint, Oil and Varnish Merchants.
  Millers.
  Water Works Chemists.
  Ceramic Works.
  For estimating per cent. of Carbon in Steel.
  For estimating per cent. of Ammonia.
 