A dye differs from a pigment in that a dye
Correct answer: C. is soluble in the medium and becomes attached to the fibre
- A. is always black
- B. is insoluble and sits on the surface as fine particles
- C. is soluble in the medium and becomes attached to the fibre
- D. contains no colour at all
Explanation
A dye dissolves and bonds to the fibre by ionic, hydrogen or covalent bonds, so the colour becomes part of the material and resists washing, whereas a pigment is insoluble and must be held in place by a binder as in paint. This is why a dyed cloth keeps its colour through the wash while a painted surface can flake. Fastness to washing and to light is the main measure of dye quality.
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About Dyes
Dyes are coloured organic compounds that form a stable bond or strong attraction with fibres, while pigments are generally insoluble and need a binding medium. The topic covers chromophores, auxochromes and conjugated systems, as well as acid, basic, direct, reactive, azo and mordant dyes.
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