Dyeing studies of wool fibers with madder (Rubia tinctorum) and effect of different mordants and mordanting procedures on color characteristics of dyed samples

In this work, the dyeing behavior of wool fabrics with madder was studied. The effect of different mordants (potassium dichromate, stannous chloride, alum, ferrous sulfate, lime, copper(I, II) sulfate, cobalt chloride, and nickel chloride) with three mordanting procedures (pre-, meta-, and post-mordanting) on color characteristics of the dyed samples was also investigated. The adsorption of madder on wool fibers was found to follow Freundlich type of isotherm. The addition of salt and acid (pH 4.5) to the dyebath increased the dye adsorption. Mordanting with different mordants and mordanting procedures showed a variety of color characteristics of the dyed wool fabrics. The results showed that all color characteristics of the dyed samples were in the first quadrant of CIE L (*) a (*) b (*) color space. Mordanting with potassium dichromate, ferrous sulfate, and copper(I, II) sulfate showed the darker shades and lower chromaticity values while stannous chloride and alum gave the lighter shades and higher chromaticity values. The minimum color difference (Delta E) was obtained from mordanting with the chlorides of cobalt and nickel. The wash and light fastness of the mordanted samples were higher than those of the un-mordanted one.