Colorants are used in many industries - to colour clothes, paints, plastics, photographs, prints, and ceramics. Colorants are also now being used in novel applications and are termed functional (high technology) as they are not just included in the product for aesthetic reasons but for specific purposes, for example in surgery.
Colorants can be either dyes or pigments. Dyes are soluble coloured organic compounds that are usually applied to textiles from a solution in water. They are designed to bond strongly to the polymer molecules that make up the textile fibre.
Pigments are insoluble compounds used in paints, printing inks, ceramics and plastics. They are applied by using a dispersion in a suitable medium. Most pigments used are also organic compounds.
Manipulating the colour and application of dyes
This section considers some of the chemistry behind the colour of dyes and how the target material, for example a fibre, influences the method of dyeing and the dye used.
A dye in solution is coloured because of the selective absorption of certain wavelengths of light by specific bonds in the molecule. The light that is transmitted is seen by the observer and appears coloured because some of the wavelengths of the visible spectrum are now missing.
