Technology of bleching:

Bleaching cab be carried out using following three ways:
i) Batch process
ii) Semi-continuous process
iii) Continuous process

Let us discuss these processes one by one:

i) Batch process: 
We can devide batch process in two categories:
a) Fabric bleaching: Kier bleaching, Bleaching in Jigger, Bleaching in winch & Softflow
b) Bleaching of yarn using cabinet and cheese machine

a) Fabric bleaching:

1. Kier Bleaching: Most common process in batch wise process is kier bleaching.  In such process fabric is first desized and then scoured and bleached (Combined process) in kier. Soem time desized and scoured fabric is also taken to kier for bleaching. Hydrogen peroxide is used as bleaching agent. Folling steps may be taken in kier bleaching:

- Loading fabric in kier
- Raisong temperature of bleach liquor slowly to 90-95 degree C with an intermediate holding of 10 minutes at 70-75 degree C to allow any trapped air escape
- Bleaching for about 3 hours  at 90-95 degree C
- Wahing with hot water on rope washing machine

The application of pressure kier can reduce time 1-2 hours as the process temperature is 120 degree C.

After the peroxide bleaching the fabric is thoroghly washed and treated with peroxide killer to remove residual peroxide.

Following recipe may be used for kier bleaching:

Fabric which is desized only:
Hydrogen peroxide (35% Conc.) for desized only: 3-0-5.0 %
Sodium Silicate for desized only: 2.0-3.0 %
Sodium Hydroxide for desized only: 0.6-1.4%
Wetting agent for desized only 0.1-0.2%

Fabric which is desized & Scoured:
Hydrogen peroxide (35% Conc.) for desized & scoured : 1.0-2.0 %
Sodium Silicate for desized & scoured : Not required
Sodium Hydroxide for desized & Scoured: 0.4-0.8%
Wetting agent for desized and scoured: 0.1-0.2%