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Light and Colour Theories, and their relation to light and colour standardization

Light and Colour Theories, and their relation to light and colour standardization
Category: Light / Color
Title: Light and Colour Theories, and their relation to light and colour standardization
Release Date: 2018-06-15
Type book: Text
Copyright Status: Public domain in the USA.
Date added: 27 March 2019
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LIGHT AND COLOUR THEORIES

Tintometer.
Form of Instrument for Opaque Observation.
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 COLOURED BY HAND

Logo

London
E. & F. N. SPON, Limited, 57 HAYMARKET
New York
SPON & CHAMBERLAIN, 123 LIBERTY STREET
1915


[v]

CONTENTS

 PAGE.
List of Platesvii
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 20
CHAPTER VIII.[vi]
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 erroneouslyplaced between the Violet and the Red; it should bebetween the Blue and the Violet.

Page 40.—Fifth line from the bottom, for Fraunhoper readFraunhofer.

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


[vii]

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

[ix]

PURPOSE

The purpose of this work is to demonstrate thatcolour is a determinable property of matter,and to make generally known methods of colouranalysis and synthesis which have proved of greatpractical value in establishing standards of purityin some industries.

The purpose is also to show that the methods arethoroughly scientific in theory and practice, andthat the results are not likely to be changed byfurther discoveries. Also that out of the work donea new law has been developed, which the writer callsthe Law of Specific Colour Development, meaningthat every substance has its own rate of colourdevelopment for regularly increasing thicknesses.

THE THEORY.

Of the six colours in white light—red, orange,yellow, green, blue and violet; Red, Yellow andBlue are regarded as dominants, because they visuallyhold the associated colours orange, green and violetin subjection.

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

[x]

The coloured glasses are called absorbents. Thered absorbent transmits violet, red and orange, butthe red ray alone is visible as colour, until the otherabsorbents are superimposed, and the character ofthe group of rays changed. In the same way yellowtransmits orange and green, and blue transmitsgreen and violet, whilst the yellow and blue aloneare visible as colour. Orange, green and violetare here called subordinates, which may be developedas follows:—

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

Twenty-five years’ experience in the applicationof the theory and the method to the requirementsof practical work, have given no reason for change.Following will be found a list of awards fromInternational Juries and Scientific Societies, also alist of industries in which the writer’s method isgiving entire satisfaction.

Awards by International Juries.
St. Louis1 Silver Medal.
2 Bronze Medals.
Brussels1 Gold Medal.
3 Silver Medals.
TurinDiploma 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—
[xi]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.
For estimating Colours for Anthropological Classifications.
For estimating Smoke Densities.
For estimating Haemoglobin in the Blood.
For estimating Colour of Whale Oil, etc., etc.

[xii]

THE METHOD.

The colour composition of any object may bemeasured by superimposing units of different coloursuntil the colour of the object is matched. A convenientapparatus is furnished for this purpose. Thecomposition of the colour is learned by merely readingthe markings on the glasses.

It is of course necessary that in the isolation ofcolour rays, some unit for measuring the intensityof both light and colour be established. As willbe explained later, all such units are necessarilyarbitrary. In this method the unit has been establishedby taking the smallest amount of colour easilyperceptible to the ordinary vision. This unit or“one” is divided into tenths in the darker shades,and hundredths in the lighter scale. One one-hundredthis the smallest amount of colour measurableby a normal trained vision.

When equivalent units in the three colours aresuperimposed, their equivalent value (not their aggregatevalue) represents so much white light absorbed.For instance, 2 R. + 2 Y. + 2 B. absorbs two unitsof white light.

When the absorptive power of the colour standardsis less than the intensity of the light, associated whitelight remains.

JOSEPH W. LOVIBOND.

The Colour Laboratories,
Salisbury.

December, 1914.


[1]

Light and Colour Theories


CHAPTER I.
Introduction.

It may at first appear strange that colour, oneof the most important indices of value in theArts, Manufactures, and Natural Products, shouldhave no common nomenclature or reliable standardfor reference, the reproduction of a given colourdepending for exactitude on the memory of a sensation;whereas this branch of science requires aphysical means of recording a colour, with a powerof recovery. It remains to be shown that thispower of record and recovery is possible, and dependsonly on the observance of a few simple natural lawseasy of application.

The study of colour is carried on by two principalmethods: the spectroscopic, where the colours arepartially separated as a continuous band by a regularvariation in their indices of refraction, the coloursgradually merging into each other by overlappingin opposite directions; or by absorption, where acolour is developed by absorbing its complementary,and is isolated as a single or complex colour. Thislatter is nature’s own method.

It is necessary to touch on some theoretical differenceswhich exist between Scientists and Artists,as to which are Primary colours, as confusion of this[2]character retards investigation. Scientists adoptRed, Green, and Violet as Primaries, regarding allother colours as mixtures of these; whilst Artistsand Colourists adopt Red, Yellow and Blue as thePrimaries, and all other colours as made from them.

The theory of the Scientists is based on the phenomenadeveloped by mixing coloured lights takenfrom different parts of the spectrum. This is amethod of synthesis, each added colour being aprogressive stage towards the complexity of whitelight. In this case the colour developed is that ofthe preponderating ray of a complex beam. Thetheory of the Artists is based on the phenomenadeveloped by mixed pigments. This is a methodof analysis, tending towards ray simplicity, eachadded pigment reducing the complexity of thecolour developed by its power of selective absorption.

The theoretical differences between the two schoolsappear to have arisen from supposing that a givencolour developed by the two methods should correspond;but considering the differences in their raycomposition, this would be impossible, for althoughboth may be describable by one general colour term,as for instance a Red, they would be of two varieties.It remains to be shown that one theory maycover both sets of phenomena.

The Red, Green, and Violet theory appears to bebased on two principal assumptions: first thatthere are only three fundamental colours;

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