Discharge technique in fabric is to make the design pattern on dyed fabric by chemical means. Diluted sulfuric acid agent is painted with a brush directly on the indigo dyed fabric. Chemical reaction takes place as the acidic agent get in contract with the indigo dye. The acidic agent will then discharge the indigo pigment, leaving a white pattern. This method of pattern making allows more freedom in expression. But most of the time, stencils are used in production because of labour. The discharge fabric is finally rinsed in an alkaline bath to remove the acidic remains.
Here is a DIY version of the same technique, you can try it at home!
Discharge dyeing works with the removal of the dye originally applied to the fabric. In this case, it was originally a red piece of fabric using a dye remover was applied through a stencil resulting in a pattern of the red colour. This technique was introduced into China in the 50s which became very popular in the rural area. Traditional fabric dyeing technique in China are based on vegetable dye where the intensity of the colour will run through time and wash. Discharge dyeing was most welcomed as the colour stays and the patterns are fine. This fabric has a butterfly and flower print.