Study the effect of ammonia post-treatment on color characteristics of annatto-dyed textile substrate using reflectance spectrophotometery

•Bixa orellana is an abundantly growing prominent dye plant.•B. orellana was tested for dyeing properties on wool fiber.•Effect of ammonia concentration on color parameters and fastness properties was investigated.•Ammonia post treatment improved color strength and depth of shades.

This research is aimed to study the influence of ammonia after-treatment on color behavior in wool yarns dyed with annatto extract. The dyeing was carried out using 15% (o. w. f.) dye concentration in presence of stannous chloride as a mordant and then treated with different percentages of ammonia solution. At the same time, color strength, CIE-Lab values and fastness properties of all dyed woolen yarns were also assessed. It was concluded that, in all cases after treatment with ammonia caused a decrease in lightness (L*) values, there was less lightness in the red hue of the wool yarns with the increase of ammonia percentage in solution. The K/S value of annatto dyed wool was found to increase after treated with ammonia. In addition, it was also observed that dyed wool yarns after post-treatment with ammonia did not return to their original color on acidification.