Reflectance colour measurement liquids

One of the major problems with these kind of products is the effect of particle size. In order to minimise grind size effects in ground coffees of different roasts. Little and MacKiimey (1956) standardised on a very fine grind with maximum hghtness value. Seakins (1971) tackled the problem by another means and developed a method to measure the colour of casein by immersing it in a liquid of similar refractive index. Reflectance measurement of dry sample preparations resulted in poor separation of colour grades because reflectance increased as particle size decreased. However, when transmittance values were measured on the liquid suspension, the colour grades were clearly differentiated. 

Cholesteric liquids can rotate polarized light to a large degree, such as some thousand degrees per 1 mm layer thickness for visible light [258]. Because of different absorption of the two polarized components in the cholesteric liquid, the material shows dichroism. Most of the effects are applied practically. The colour change in reflection with temperature of a cholesteric liquid can be used for very sensitive temperature measurements of 0.001°C It is even possible to construct infra-red/visible image converters with cholesteric liquid crystals. 

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