PLATE I
ILLUSTRATING THE POSITION OF THE PRIMARIES IN RELATION TO THE COLOURS REQUIRED TO BE PRODUCED BY THE THEORETICAL MIXTURES AND ALSO IN RELATION TO THE CHROMATIC CIRCLE.
To face page 4.[Lovibond, Colour Theories.
CHAPTER II.
Evolution of the Method.
The writer was formerly a brewer, and this work had its origin in an observation that the finest flavour in beer was always associated with a colour technically called “golden amber,” and that, as the flavour deteriorated, so the colour assumed a reddish hue. It was these variations in tint that suggested the idea of colour standards as a reliable means of reference.
The first experiments were made with coloured liquids in test tubes of equal diameter, and by these means some useful information was obtained; but as the liquids soon changed colour, frequent renewals were necessary, and there was always a difficulty and uncertainty in their exact reproduction.
To obviate this, glass in different colours was tried, and long rectangular wedges with regularly graded tapers were ground and polished for standards, whilst correspondingly tapered glass vessels were made for the beers. These were arranged to work side by side, and perpendicularly, before two apertures of an optical instrument, which gave a simultaneous view of both. The apertures were provided with a fixed centre line, to facilitate the reading off of comparisons of thickness. There was no difficulty in obtaining glass which approximated to the required colour when used in one thickness only. But as thickness varied, the test no longer held good for both standards, their rates of colour change being different, making the method unreliable.[1]
The system about to be described is one of analytical absorption, and has been published from time to time in the form of papers, read before Societies interested in the question of colour standardization; as also in two descriptive works by the present writer. The earlier works were necessarily fragmentary, but gathered system as the subject progressed.