Metal mordanting in dyeing with natural colourants

Abstract

Metal mordanting, or the application of metal salts, is a common method of improving the light fastness in dyeing with natural colourants. This review presents the results from a survey of the literature on metal mordanting to assess what levels of correlation exist between mordant‐induced effects (changes in colour and colour depth) and the changes in light fastness, what is known about the mechanisms of mordant‐induced improvements of light fastness, and how the salt levels used in coloration processes compare with the limits on metal levels in wastewater and on the dyed substrates. No strong interrelationships are found between the mordant‐induced effects and light fastness improvements. Knowledge about mechanisms of mordant effect on light fastness appears, in large part, to be derived from empirical correlations. However, as light fastness is affected by a multitude of factors, the correlations do not always hold true. It is found that residual metal contents in spent dye/mordanting liquors are generally not reported. However, with rough calculations, it is estimated that, with even the lowest reported salt concentrations, the metal contents in spent liquors exceed environmental release limits. The metal contents on dyed substrates are also not generally reported, but similar estimations show that the contents of heavy metal on dyed substrates (when copper and chromium salts are used as mordants) also exceed limits. On the basis of these observations, the authors make suggestions for elements to be included in investigations on furthering the use of natural colourants in textile dyeing.

A physicochemical characterisation of a medieval herbal ink, Mahī, of Assam, India

“…Hence, the colour coordinate analysis was performed for numerical characterisation of colour. The colour measurements were expressed in terms of CIELAB values using M1 as the control, as the ingredients of M1 are present in all of the Mahī samples. The calculated results are reported in Tables and .…”

“…of CIELAB [46,47] values using M1 as the control, as the ingredients of M1 are present in all of the Mah ı samples. The calculated results are reported in Tables 4 and 5.…”

A new way to improve the light-fastness of azo reactive dyes through the introduction of benzene sulfonamide derivatives into the triazine ring

“…Therefore, the development of a strategy to improve the light-fastness of azo dyes is of great importance and current interest. Generally, there are two ways to improve the light-fastness of azo dyes: rst, the use of chromophores, such as anthraquinone and metal azo complexes, with high light-fastness, [13][14][15] and second, the incorporation of UV absorbers into the dye molecules or the treatment of textiles with UV absorbers before or aer dyeing. [16][17][18][19][20][21][22] UV absorbers are usually introduced into a dye molecule by linkage with cyanuric chloride, 17 and the latter also acts as a reactive group in a reactive dye.…”

Modification of cotton fabrics with a hydrolysed organotrialkoxysilane/metal alkoxide system: multifunctionalisation and mordant dyeing

“…The type of mordant also has a significant impact on the colour of the dyed textile, as well as on the colour fastness to washing, light, and perspiration [13][14][15][16][17][18][19]. Inorganic, water-soluble salts of chromium, aluminium, iron, and copper are also used by natural dyers.…”

“…Inorganic, water-soluble salts of chromium, aluminium, iron, and copper are also used by natural dyers. The type of mordant also has a significant impact on the colour of the dyed textile, as well as on the colour fastness to washing, light, and perspiration [13][14][15][16][17][18][19].…”