Natural dyeing of khadi cotton using rare earth salts as mordant with annatto extract

Purpose Replacing conventional mordants by benign mordants, rare earth (RE) salts have been used in the process of natural dyeing with annatto seed extract. The purpose was threefold – first, to increase the dye uptake through these new mordants; second, to have better fastness properties of dyed swatches and third, to have lesser effluent pollution, as the new RE mordants are used in one-tenth quantities only. Design/methodology/approach Sustainable natural dyeing was attained by using RE salts as mordant in one-tenth quantity, for natural dyeing, replacing the conventional mordants such as alum and ferrous sulphate. Annatto extract has been used as natural dye. Findings Through the study, it was inferred that the natural dyeing using annatto seed extract gives very good colour depth on the dyed swatches and also shows marked improvement in fastness properties. Research limitations/implications Research implication is that often it is expected that any new chemical used in the textile processing adds on to the effluent load; however, contrary to that, this study found that the use of RE salt is very beneficial as it is used in smaller quantities, but gives far better dyeing results. Practical implications RE salts can be used in natural dyeing without causing any harm to the environment and dyers. Social implications Use of RE salts in natural dyeing is a new concept. It is a very safe technology and can be used without causing any harm to the environment and the dyers. Originality/value This study is unique as it focuses on the use of RE salts in natural dyeing replacing the conventional mordants, which are used ten times more in quantity.