Abstract
Optical properties of paper are those that govern its visual appearance-mainly, colour, opacity and gloss. These depend on the fact that paper consists of a network of doubly refractive transparent fibres immersed in air as medium and, in some cases, the optical properties can be expressed in terms of the absorption and scattering coefficients of the fibres and loading materials.
Opacity is the property most thoroughly understood and there is a British Standard for its measurement. The colorimetry of near-white papers still gives rise to difficulties, particularly with those containing optical bleaches and recent work on the assessment of sheets containing appreciable amounts of fluorescent materials is reviewed. The measurement of gloss is the most difficult to perform and our knowledge here is still far from complete. Little-known research on gloss done during the past fifteen years at PATRA and by a group of Japanese workers is summarised.
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