GATE (TF) Textile 2009 Question Paper Solution | GATE/2009/TF/45

Bleaching cotton with hydrogen peroxide is a common method used to lighten or remove color from cotton fabrics. Here’s a general process for bleaching cotton with hydrogen peroxide:
Preparation: Start by selecting a well-ventilated area for the bleaching process. It’s advisable to wear protective gloves and clothing to prevent skin contact with the bleach solution.
Fabric Testing: Before bleaching the entire fabric, it’s a good idea to test a small, inconspicuous area of the cotton fabric to ensure that the fabric can withstand the bleaching process without damage or excessive weakening. This step is particularly important for colored or patterned fabrics.
Dilute Hydrogen Peroxide: Prepare a solution of hydrogen peroxide and water. The concentration of hydrogen peroxide may vary depending on the desired level of bleaching. Generally, a solution of 3% hydrogen peroxide (commonly found in drugstores) diluted with an equal amount of water is suitable for most cotton bleaching applications.
Soaking: Submerge the cotton fabric in the hydrogen peroxide solution, ensuring that the fabric is completely saturated. You can either place the fabric in a container filled with the bleach solution or use a large basin or sink.
Agitation: Gently agitate the fabric in the bleach solution to ensure even distribution and contact between the fabric and the bleach. You can use a wooden spoon or your hands (wearing gloves) to stir the fabric gently.
Time and Monitoring: The duration of the soaking process will depend on the desired level of bleaching and the fabric’s reaction to the bleach. Start with a shorter duration (e.g., 10-15 minutes) and check the fabric periodically to observe the color change. If the desired level of bleaching hasn’t been achieved, you can continue soaking for longer, checking the fabric regularly.
Rinse: Once the desired level of bleaching is achieved, thoroughly rinse the fabric with cold water to remove the hydrogen peroxide solution. Rinse until the water runs clear, ensuring no residual bleach remains.
Neutralization: To neutralize any remaining bleach and prevent further bleaching, prepare a solution of water and vinegar (1 part vinegar to 4 parts water) or a commercial color-safe fabric bleach neutralizer. Submerge the fabric in this solution for a few minutes, then rinse again with cold water.
Washing: After rinsing, wash the bleached fabric separately using a mild detergent. Follow the care instructions provided for the specific fabric to ensure proper washing and maintenance.

Note: It’s important to exercise caution when working with hydrogen peroxide, as it can cause skin and eye irritation. Additionally, hydrogen peroxide may weaken fabric fibers, so prolonged exposure or excessive concentrations may damage the fabric. Always test a small area of the fabric and monitor the bleaching process carefully to achieve the desired results without compromising the fabric’s integrity.