Definition of natural dyes/colouants :
The word ‘natural dye’ covers all the dyes derived from the natural sources like plants,
animal and minerals. Natural dyes are mostly non-substantive and must be applied on
textiles by the help of mordants, usually a metallic salt, having an affinity for both the
colouring matter and the fibre. Transition metal ions usually have strong co-ordinating
power and/or capable of forming week to medium attraction/interaction forces and thus
can act as bridging material to create substantivity of natural dyes/colourants when a textile
material being impregnated with such metallic salt (i.e. mordanted) is subjected to dyeing
with different natural dyes, usually having some mordantable groups facilitating fixation of
such dye/colourant. These metallic mordants after combining with dye in the fibre, it forms
an insoluble precipitate or lake and thus both the dye and mordant get fixed to become
wash fast to a reasonable level.
animal and minerals. Natural dyes are mostly non-substantive and must be applied on
textiles by the help of mordants, usually a metallic salt, having an affinity for both the
colouring matter and the fibre. Transition metal ions usually have strong co-ordinating
power and/or capable of forming week to medium attraction/interaction forces and thus
can act as bridging material to create substantivity of natural dyes/colourants when a textile
material being impregnated with such metallic salt (i.e. mordanted) is subjected to dyeing
with different natural dyes, usually having some mordantable groups facilitating fixation of
such dye/colourant. These metallic mordants after combining with dye in the fibre, it forms
an insoluble precipitate or lake and thus both the dye and mordant get fixed to become
wash fast to a reasonable level.
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