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Laboratory dyeing experiments, carried out with direct dyes on immature and mature cotton fibres of known origin, showed that the maturity did not affect the amount of dye absorbed at equilibrium. The absorption and desorption rates, however, were higher for immature than for mature fibres. Mercerisation of the fibres before dyeing did not greatly affect the differences.

The causes of why immature fibres in general and especially in neps look lighter in colour than the rest of the fabric are discussed. A theory is put forward that, besides the effect of optical differences, the differences in depth are caused by the more rapid desorption of dye from immature fibres. Such differences would be exaggerated by unsuitable processing conditions, e.g. during rinsing, which was confirmed by some laboratory dyeings on fabric samples.

From the results, it was predicted that, in order to obtain an even colour on a fabric containing immature as well as mature fibres, dyeing should not be carried on until equilibrium is reached and that rinsing and aftertreatments should be carried out so that the dye desorption will be as small as possible.