Page 22 - Basic Principles of Textile Coloration

MODERN TEXTILES 11

8 ´ 108 kg of a few thousand different dyes and pigments. The textile coloration
industry is not only large but also extremely diverse.

1.2.2 Textile manufacture

Textile consumption is closely related to growing world population and consumer
affluence. To satisfy market demand for fabric, fully automated, high-speed
production, with a minimum of defects, is essential. The following outline of
textile manufacture identifies the major processes, the division of operations, and
situates coloration in the overall scheme. Chapter 2 provides more details on fibres
and textile manufacturing.

Cotton and wool are only available as short staple fibres of pre-determined
length, but artificially made fibres are available either as continuous filaments or
short fibres cut to any required length. Textile manufacturing using natural fibres
starts with the opening, separation and mixing of short fibres. The carding process
draws them out into a band of parallel fibres (sliver), and drawing out and twisting
of this yields spun yarn. Opening, carding or drawing may also serve to blend two
or more staple fibres; for example, cotton and staple polyester. Continuous
filaments do not require such preliminary operations.

The major methods of fabric assembly from yarns of staple fibres, or from
continuous filaments, are weaving and knitting, both of which, being fully
automated, have significant production rates.

The production of a textile material from fibres involves a defined sequence of
operations to produce yarns and assemble them into fabric. Each process is a
necessary prerequisite for the next. The situation of dyeing in the production
scheme, however, is not necessarily rigidly defined. Dyeing may occur at any stage
during textile manufacture: on loose fibre, or on the intermediate forms such as
sliver or yarn, or on fabric, towards the end of the manufacturing cycle. Even
garments and finished articles can be dyed. This means that a variety of dyeing
machines is required for the different types of textiles. Dyeing usually involves
contact between an aqueous solution or dispersion of the dyes and the textile
material, under conditions that promote substantivity and produce uniform
coloration throughout. Printing, on the other hand, is the localised application of
different dyes to different specific areas on one face of a fabric, according to some
predetermined colour design. This book primarily discusses textile dyeing but
Chapter 23 deals with printing.

Before textile fibres are dyed, they are washed or scoured to remove natural