The finishing process, known as bleaching, consists of a series of steps that prepare textiles to be used as white color, making them suitable for dyeing and printing processes. Generally, bleaching is considered a pre-finishing process used in the textile industry. However, it is often referred to in the market as “bleaching” and includes cooking and bleaching. Other pretreatment processes are referred to by their original names.
Raw cotton fiber contains a variety of impurities, including waxes and oils that impart hydrophobic properties, pigments that give it a yellowish color, and leaves, litter and ginning residues that can be mixed in during harvest. Although some of these impurities are removed during yarn production, some of them can be transferred to the woven fabric. These factors spoil the appearance of the fabric and complicate subsequent finishing processes such as dyeing and printing. Therefore, bleaching is applied to remove the undesirable properties and prepare the fabric.
**1. Spinning:** It is done to remove foreign materials such as dirt, oils, plant residues, leaf and seed residues on the fabrics woven from raw cotton. It is a critical stage especially for fabrics to be dyed in dark colors. Also, for fabrics that will be sold in light colors or used for printing, the cooking process may be lighter. This process increases the fabric’s ability to absorb water, absorb chemicals and absorb dyes. Also, for fabrics containing polyester, this process removes production oils from the surface of the polyester. The baking process is usually carried out using chemicals such as sodium hydroxide.
**2.Bleaching:** It is a bleaching process to destroy colored pigments in the fabric and to dissolve vegetable residues. Bleaching agents such as hypochlorite, sodium chlorite and hydrogen peroxide are commonly used for this process. However, hydrogen peroxide bleaching is preferred as an environmentally friendly option. This bleaching method can be applied without the need for cooking. The bleaching process improves the coloration of the fabric and the results of dyeing processes.
Spinning and bleaching is one of the key steps in the textile industry and helps the fabric to achieve better results in downstream processing.
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