Dyeing

Dyeing  is  the  process  of  imparting colors to  a  textile  material  in  loose  fiber, yarn, cloth or garment form by treatment with a dye. Dyeing is also the process of coloring textile materials by immersing them in an aqueous solution of dye, called dye liquor. Normally the dye liquor consists of dye, water and an auxiliary.  To  improve  the  effectiveness  of  dyeing,  heat  is  usually  applied  to  the dye liquor. Dyeing can be done at any stage of the manufacturing of textile- fiber, yarn, fabric or a finished textile product including garments and apparels. The property of color fastness depends upon two factors- selection of proper dye according to the textile material to be dyed and selection of the method for dyeing the fiber, yarn or fabric.

Dyeing Methods:

Colour  is  applied  to  fabric  by  different  methods  of  dyeing  for  different types  of fiber and at different stages of the textile production process. Dyeing can be done during any stage in the textile manufacturing process. Textiles may be dyed as fibre, as yarn, as fabric, as garments, depending upon the type of the fabric or garment being produced.These  methods  include 

• Direct dyeing
• Stock  dyeing
• Top dyeing
• Yarn  dyeing
• Piece dyeing
• Skein (Hank) Dyeing 

Solution pigmenting or dope dyeing; Garment dyeing etc. Of these Direct dyeing and Yarn Dyeing methods are the most popular ones.

Direct Dyeing 

When a dye is applied directly to the fabric without the aid of an affixing agent, it is called direct dyeing. In this method the dyestuff is either fermented (for natural dye) or chemically  reduced  (for  synthetic  vat  and  sulfur  dyes)  before  being  applied.  The  direct dyes,  which  are  largely  used  for  dyeing  cotton,  are  water  soluble  and  can  be  applied directly to the fiber from an aqueous solution. Most other classes of synthetic dye, other than vat and sulfur dyes, are also applied in this way.

 

Stock Dyeing

Stock  dyeing  refers  to  the  dyeing  of  the  fibers,  or  stock,  before  it  is  spun  in  to yarn.  It  is  done  by  putting  loose,  unspun  fibres  in  to  large  vats  containing  the  dye  bath, which is then heated to the appropriate temperature required for the dye application and dyeing process.

Stock  dyeing  is  usually  suitable  for  woolen  materials  when  heather  like  color effects are desired. Wool fibre dyed black, for example, might be blended and spun with un-dyed (white) wool fibre to produce soft heather like shade of grey yarn. 

Tweed fabrics with heather like color effects such as Harris Tweed are examples of stock dyed material. Other examples include heather like colours in covert and woolen cheviot.

Top Dyeing

Top dyeing is also the dyeing of the fibre before it is spun in to  yarn and serves the same purpose as stock dyeing – that is, to produce soft, heather like color effects. The term top refers to the fibres of wool from which the short fibres have been removed. Top is  thus  selecting  long  fibres  that  are  used  to  spin  worsted  yarn.  The  top  in  the  form  of sliver is dyed and then blended with other colors of dyed top to produce desired heather shades.

Yarn Dyeing

Yarn  dyeing  is  the  dyeing  of  the  yarns  before  they  have  been  woven  or  knitted  into  fabrics. Yarn  dyeing  is  used  to  create  interesting  checks,  stripes  and  plaids  with  different-colored  yarns  in  the  weaving  process.  In  yarn  dyeing,  dyestuff  penetrates  the  fibers  in  the  core  of  the  yarn.  There  are  many  forms  of yarn dyeing- Skein  (Hank) Dyeing, Package Dyeing, Warp-beam Dyeing, and Space Dyeing.

Piece Dyeing

The dyeing of cloth after it is being woven or knitted is known as piece dyeing. It  is  the  most  common  method  of  dyeing  used.  The  various  methods  used  for  this  type  of  dyeing include jet dyeing. Jig dyeing, pad dyeing and beam dyeing.  

Skein (Hank) Dyeing
The yarns are loosely arranged in skeins or coils. These are then hung over a rung and immersed in a dyebath in a large container. In this method, the colour penetration is the best and the yarns retain a softer, loftier feel. It is mostly used for bulky acrylic and wool yarns.