Color Measuring And Matching Of Colored Fiber Blends

Color is one of the most important attributes of a textile material. An accurate reflectance measured with spectrophotometer is the base for representing color attributes and color matching. It is sometimes advantageous to have the fiber samples behind glass. This is caused by having to enclose the sample within a pressure cell to keep the sample from contaminating the sphere of the instrument. However, even if good flat optical quality glasses are employed, great inaccuracies would arise. Therefore, it is necessary to minimize the errors caused by the optical glass.Natural colored cotton, a kind of eco-friendly colored textile fiber, has once again been paid attention to as a promising substitute for present textiles because of no use of highly toxic dyes and chemicals. It could be used in the same way as pre-colored fibers to manufacture variety of textile products. The color matching of colored fibers would be very useful in producing such kind of textile materials. It is no doubt that the natural colored cotton will have a promising future.The arts of color matching of colored fiber blends dated back many years. Single-constant KUBELKA-MUNK theory normally being used in textile industry can not give accurate predictions when applied to fiber blends. Various empirical and semi-empirical methods are developed to color matching process of pre-colored fiber blends. However, no mature theory has been established in world wide up to now, indicating nothing of practical and effective color matching system.In the first part of this thesis, a correction method for reflectance measured with optical glass is proposed. The method consists of a correction algorithm that gives different correction coefficient for reflectance at different wavelength, and a measurement of transmittance of the glass. The proposed algorithm has been tested with materials of various forms. The corrected reflectance agrees very well with true one and their color differences fall below the acceptable limit, which shows the validity of the correction algorithm. The correction method could be used not only for fiber-forming materials, but also for powder-forming, granulate-forming and filament-forming materials etc.The second part has studied color matching of pre-colored fiber blends. Linear-least-squares regression has been used for calculation of scattering coefficient(K) and absorption coefficient(S), which are the base data of color matching. Colorimatric color matching of pre-colored fiber blends has been achieved based on two-constant KUBELKA-MUNK theory. Then, some modifications of Allen's algorithm have been made. The modifications include setting the average of primaries scattering coefficient as initial value and removingconstrain unit sum of concentration, as well as expanding the number of primaries in the close match procedure. The tri-stimulus color matching of pre-colored fiber blends based on the modified matching process shows a satisfactory result. That is, predicted recipes are nearly same as true blended ratios and color difference are within acceptable limit.In the last part, color characteristic of pre-colored fiber blends/natural colored cotton has been studied. Chromaticity diagrams of these blends have been drawn according to their tri-stimuli, which shows the color matching scope of these fiber blends. Special chromaticity characteristic of fiber blends such as dominant wavelength, excitation purity and chromaticity purity were calculated to describe their color attributes.An accurate color measurement is crucial for the color representative, and the correction method proposed here for reflectance measured with optical glass is basis for further studies and application such as color matching, color difference.The results of computer color matching for colored fiber blends based on the two-constant KUBELKA-MUNK theory lay the foundation on the matching algorithms and computer programming for practical use.The chromaticity diagram and characteristics of colored fiber blends/natural colored cotton sh...