In the process of semi-continuous dyeing that consists of pad-batch, pad-jig, pad-roll the fabric is first impregnated with the dye-liquor in, what is called a padding machine. Then it is subjected to batch wise treatment in a jigger. It could also be stored with a slow rotation for many hours. In the pad-batch this treatment is done at room temperature while in pad-roll it is done at increased temperature by employing a heating chamber. This helps in fixation of the dyes on to the fibre. After this fixation process, the material in full width is thoroughly cleansed and rinsed in continuous washing machines. There is only one point of difference between Continuous and semi-continuous dyeing process is that in semi-continuous dyeing, the dye is applied continuously by a padding. The fixation and washing remaining discontinuous. Liquor Ratio in semi-continuous dyeing is not of much importance and is not taken as a parameter. One of the widely used techniques for semi-continuous dyeing process is the Pad Batch Dyeing a schematic diagram is given here for the semi-continuous dyeing process.



The following table shows some of the important machineries for semi-continuous and continuous dyeing processes.

Pad Batch Dyeing is one of the widely used technique for semi-continuous dyeing process. It is mainly used in the dyeing of cellulosic fibre like cotton or viscose (knit and woven fabric) with reactive dyes. Pad batch dyeing is a textile dyeing process that offers some unique advantages in the form of versatility, simplicity, and flexibility and a substantial reduction in capital investment for equipment. It is primarily a cold method that is the reason why it is sometimes referred to as the cold pad batch dyeing.

The technique or process used in pad-batch dyeing starts with saturating first the prepared fabric with pre-mixed dye liquor. Then it is passed through rollers. The rollers, or padders, effectively forces the dyestuff into the fabric. In the process, excess dye solution is also removed. After removal of excess dye stuff the fabric is subsequently "batched". This batching is done by either storing it in rolls or in boxes. It takes a minimum of 4-12 hours. The batches are generally enclosed by plastic films. This prevents absorption of carbon dioxide and water evaporation. Finally as the reaction is complete the fabrics are washed. This is done by becks, beams, or any other washing devices.

• Significant cost and waste reduction as compared to other conventional dyeing processes.
  
  
• Total elimination of the need for salt and other specialty chemicals. For example there is no need for anti-migrants, leveling agents and fixatives that are necessary in conventional dyebaths.
  
  
• Optimum utilisation of dyes that eliminates specialty chemicals, cuts down chemical costs and waste loads in the effluent. All this results in a formidable reduction in wastewater treatment costs.
  
  
• Excellent wet fastness properties.
  
  
• Pad batch dyeing cuts energy and water consumption owing to low bath ratio (dye:water) required for the process. This is because unlike other dyeing processes it does not function at high temperatures.
  
  
• A uniform dye quality is achieved with even color absorbency and colour fastness.
  
  
• As compared to rope dyeing, Pad batch dyeing produces much lower defect levels.
  
  
• In pad batch dyeing, qualities like high shade reliability and repeatability are common. This is because of high reactivity dyes with rapid fixation rate and stability.
  
  
• Lastly Pad batch dyeing can also improve product quality. The fabric undergoing the cold pad batch dyeing process is able to retain an uniformly coloured appearance. It shows added luster and gives a gentle feel. The fabric gives a brighter look in shades.