Dye

A colored substance that bonds to or remains within a material to impart color. Dyes are distinguished from pigments, which are typically insoluble particles dispersed in a material.

Visible spectrum: The portion of electromagnetic radiation detectable by human vision, roughly spanning wavelengths from 380 to 700 nanometers. A dye’s perceived color depends on which visible wavelengths it absorbs and reflects or transmits.
Absorption spectroscopy: A set of techniques that measures how a substance absorbs light across wavelengths. Absorption spectra help characterize a dye’s color and molecular transitions.
Textile dyeing: The process of applying colorants to fibers, yarns, or fabrics so that color persists during use. It is the largest and most familiar setting for dye application.
Pigment: An insoluble colored particle dispersed in a medium rather than dissolved in it. Unlike dyes, pigments usually require a binder to adhere to a surface.
Madder: A plant source of red colorants, including alizarin, traditionally used to dye textiles. Madder illustrates the long use of plant-derived dyes before synthetic substitutes.
Chromophore: The part of a molecule responsible for absorbing light in a particular region of the spectrum. A dye’s chromophore creates its characteristic color through selective light absorption.
Conjugated system: A sequence of atoms with overlapping p orbitals that allows electrons to be delocalized across a molecule. Extended conjugation often shifts molecular absorption into the visible range, producing color.
Reactive dye: A dye that forms a covalent bond with a fiber under suitable application conditions. Reactive dyes give cellulose textiles strong color retention through chemical bonding.
Lake pigment: An insoluble pigment made by fixing a soluble dye onto an inert substrate. Lake pigments bridge dyes and pigments by turning a soluble colorant into a particle.
Indigo: A deep-blue dye produced naturally by some plants and manufactured synthetically for widespread use. Its natural and synthetic production histories mark a major transition in dye manufacture.

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