The significance of pretreatment: two objectives of bleaching

The objective of textile bleaching is to make the substrate, yarn or fabric, white. We will talk about the bleaching of fabrics on this page.

The reason for making gray weaves white through bleaching is to attain good bright colors in the subsequent dyeing stage. To prevent faulty dyeing results in the cellulose fiber, complete and thorough desizing and scouring is necessary as inferior bleaching and dyeing results are caused otherwise.

With cellulose fabric, it can be said that around 70% of all faulty bleaching, dyeing and printing results is caused by poor desizing and scouring.In the bleaching process, it is important to completely eliminate impurities that could not be removed in the preceding stages.

That is to say, the objective of bleaching is not just improved whiteness. This process has an important role in removing the sizing agent on gray fabric and other remaining impurities that could not be cleared in the preceding stages of desizing and scouring.

In other words, if the sizing agent or pectin content remains due to incomplete desizing and scouring, inferior results will be produced in the subsequent dyeing stage. To prevent this, the sizing agent and pectin content should be decomposed, by oxidation or reduction, in the bleaching stage so that improved dyeing effects can be produced.

In this series, ‘desizing and scouring’ and ‘bleaching’ will be referred to as ‘pretreatment’ collectively. Pretreatment technology is often ignored (in underdeveloped textile industries) since it is not easy, unlike that of dyeing, to assess its effect with the naked eye in the practical manufacturing environment. But that is quite a mistake.