ESTIMATION OF COLOUR DIFFERENCES IN THE CASE OF WOOL DYEING WITH NATURAL DYES EXTRACTED FROM GREEN NUTSHELL

In this paper were experimentally determined the colour differences between two pattern (standard and sample) with CIELAB formula in case of dying with natural dyes extracted from green nutshell. The dyes were made according to an experimental program at different concentration. The obtained dyes were used to estimate the colour differences that are usually a mixture of differences of brightness, saturation and nuance. In order to determine the intensity of the dyeing was measured at spectrophotometer Specord 200 the remission of the dyed samples. With their help were calculated the trichromatic values X, Y, Z and then the rectangular coordinates: L*- lightness coordinate, a* - the chromaticity coordinate for red-green colour area, b* - the chromaticity coordinate for yellow-blue colour area in CIELAB space. From these values derive the cylindrical coordinates: L*- lightness, C* -chroma, H* - nuance. The differences in colour ΔE between the samples and the standard sample are represented by distances between respective positions in CIELAB field and were calculated with some standardized relations. This colour differences were decomposed in: ΔL* - the difference in lightness ΔC* - the difference in chroma, ΔH* - the difference in nuance and calculated in CIELAB units. Were also made the diagrams: the position of the colours in CIELAB field, the chromatic diagram a*=f(b*), the lightness position and the colour differences between the samples and the standard sample.