Page 24 - Basic Principles of Textile Coloration

COLOUR, DYES AND DYEING 13

Consequently, yarn production, fabric construction, and dyeing and finishing often
take place in different locations with clear divisions between mechanical
manufacturing operations and the wet processing associated with preparation,
dyeing or printing, and finishing.

The seven major fibre types have quite different properties. The materials
produced from these have a wide variety of end-uses, and each fabric has its
particular aesthetic, colour fastness and technical requirements. There are
therefore different types of dyes and processing methods for dyeing and printing.
The manufacture of any fabric will always involve a compromise between the
desired quality and performance, and the overall production cost. Today, fully
automated and environmentally friendly processes are the norm: automation is
essential to remain competitive, and national and local governments now demand
lower levels of air and water pollution. The environmental impact of textile
production and coloration is the most significant challenge facing the industry in
Europe and North America today. Eventually, more environmentally sound
methods of production and disposal will also be forced upon producers in the
developing world as they expand further.

1.3 COLOUR, DYES AND DYEING

1.3.1 Light and colour
Colour sensation is a characteristic of human experience. Nature provides a
particularly vivid display of colour. We use colours in many varied ways; for
example, for clothes, paints, foods, lighting, cosmetics, paper, furnishings, and for
identification and security. Despite our familiarity with it, there is no simple
answer to the question ‘What is colour, and how do we see it?’: we understand so
very little of the complex processes involved in colour vision. There are three main
stages in the perception of colour, but each one consists of numerous complicated
processes:
(1) absorption of coloured light entering the eye by the sensitive cells in the

retina lining the back of the eyeball;
(2) transmission of nerve impulses from the retina to the brain via the optic nerve;
(3) interpretation of these signals when they reach the visual cortex in the brain.

To understand colour, some knowledge of the nature of light is essential. Light is a
form of energy usually considered as being propagated at high speed in the form of