RAPID ASSESSMENT OF COLOUR FOR ROUTINE STORAGE TESTING 17 MR. K. McLAR•zN: I tried this myself some years ago by making such scales, and for an individual you can assess the colour temperature of a light source over quite a wide range. If you make your scale big enough, of course, you can can go quite easily from 2,000 to 10,000øK, but the great difficulty is that the particular pair of patterns which are going to be a match under the illuminant-and that is the parameter you are measuring-varies according to the yellowhess of vision of the actual observer, as yellowhess usually follows age, but not entirely.

J. Soc. Cosmetic Chemists 18 19-31) (1967) ¸ 1967 Society of Cosmetic Chemists of Great Britain Hair colourants-a practical approach M. W. PARSLOW and B. A. SCOTT* Presented at the Symposium on "Colour", organised by the Society of Cosmetic Chemists of Great Britain in Eastbourne, Sussex, on 27th April 7966. 8ynol•i•--The developments in hair colourant products fall into two categories, improve- ments to existing dye systems and the development of novel dye systems. The relevance of colour and rate of diffusion to the development of hair colourants are exemplified. The experimental details of a rate measurement technique are given and its use in improving product performance is shown. In an excellent review, Giles (1, 2) has recently described the develop- ment of the theories of textile dyeing from the time of Robert Boyle and summarised the current state of our knowledge. He began the article with the statement "Scientists are human, colour fascinates them as it does the layman". Many scientists are now engaged in research into hair colourants and while these scientists may be fascinated by the colour of dyes and dyed hair, this is not an idle fascination since most realise the commercial implications of their research. In the last few years there has been a change in attitude towards the use of colourants by women and, to a lesser extent, towards the use by men. So today, dyeing and bleaching are not operations to be done surreptitiously, but openly and regularly. This change in attitude and use patterns has resulted in a flood of new hair colourants into sophisticated markets where a rapid growth has occurred. For example, in the U.K. the market increased by 26% in 1962-63, and 21% in 1963-64, and in the U.S.A. this year Americans are expected to spend $100M on hair colourants (3). With one or two exceptions, the new entrants to this rapidly increasing *Unilever Research Laboratory, Isleworth, Middex. 19