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The article examines the concepts of the following three quantities: partial colour sensitivity of a recipe to a particular colorant, colour balance of a recipe, and the overall colour sensitivity and the related property of colour robustness of a recipe. the way to calculate numerical estimates of the above quantities is extended from the case of CIE L *a*b* to the case CMC(l:c) colour difference formula. Results of a few numerical experiments are included for illustration and some possible practical consequences are discussed.

In a number of previous papers the results of studies of molecular orientation in poly(ethylene terephthalate) (PET) by means of refractive index measurements and infrared, Raman and fluorescence spectroscopy have been presented. The present paper attempts to correlate the results of these studies and, in particular, to explain the observation that the fluorescent molecules appear to be more highly oriented than the polymer chains. Of the two explanations considered, that which assumes that the fluorescent molecules align themselves preferentially parallel to those segments of polymer chain in which the glycol residues are in the trans conformation is the more successful. It is also shown that the development of orientation in PET can be described well in terms of a simple modification of the rubber‐network model even for large deformations.

There are large variations between different previously published lightness difference experimental data sets. Two hundred and eight pairs of matt and glossy paint samples exhibiting mainly lightness differences were accumulated. Each pair was assessed about twenty times by a panel of fourteen observers using the grey scale method. The results were used to derive a new lightness difference formula (CII), and to a large extent, a possible new CIE lightness difference formula (CMC99). Both formulae were found to be more accurate than the typical deviation of an individual assessment from the mean of a panel of 20 observers, and outperformed the existing formulae using the present data set. The new CMC99 lightness difference formula is integrated into the new CIE colour difference equation CIEDE2000. The results also showed that special attention should be paid to measuring very dark samples. This is caused by poor instrument repeatability and inter‐instrument agreement in this colour region.

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