Quality control during desizing in Denim Washing

Introduction:

Desizing in denim garment refers to the process of removing the sizing materials that are applied to the fabric during the weaving process to strengthen the yarns and improve their weaving performance. However, these sizing materials need to be removed before further processing, such as dyeing or finishing, can take place.

Quality Control Desizing of Denim garments is an essential step in the denim washing department to ensure that the garments meet the desired quality standards.

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Points to be checked before starting desizing in denim garment:

Before starting the desizing process for denim garments, it's important to check two key things: the depth of the sizing materials on the fabric and the colorfastness of the dye.

The depth of sizing materials helps determine how much needs to be removed, and the dye colorfastness determine the extent of color bleeding during desizing.

The amount of desizing chemical, time and temperature for the desizing process, should be chosen based on the observed depth of sizing materials and the dye's colorfastness.

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1.???? Depth of Sizing Materials: The depth of the sizing materials on the fabric should be checked to ensure proper Desizing. It can be measure with tactile inspection and sample weighing.

Tactile Inspection: Gently run the fingers over the fabric surface to feel for any variations in thickness. This tactile inspection can provide a sense of the sizing material's depth.

Sample Weighing: Weigh a section of the fabric before and after removing the sizing material. The difference in weight can give an indirect measure of the depth of the sizing material.

Solvent Extraction Method: ?The extraction method provides a quantitative measure of the sizing material content in a fabric swatch and is commonly used in textile analysis laboratories.

Use a suitable solvent to extract sizing material from the fabric. After extraction, evaporate the solvent and weigh the residue to determine the amount of sizing material.

The choice of solvent is depends on the specific type of sizing material used in the fabric. So, this is inherently a complex process as the efficacy of the extraction relies on selecting a right solvent based on the particular sizing agent.

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2.???? Colorfastness of Un-washed Fabric: The colorfastness of the fabric should be checked before desizing to ensure how much dye can bleed during desizing process.

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Points to be checked during desizing in denim garment:

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1. Monitor Time, Temperature, Dosing: The desizing process should be monitored closely to ensure that the correct time, temperature, and dosing of desizing agents.

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2. Proper Rinsing: After desizing, the fabric should be rinsed thoroughly to remove any residual desizing agents and unfixed dye. This can be done by using sufficient water and twice rinsing. Proper rinsing is important to ensure clean garments for subsequent processes.

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Points to be checked after desizing in denim garment:

Random Garment should be inspected after desizing to check for any remaining sizing materials or unfixed dye. A clean fabric surface is crucial for subsequent processes and the overall appearance of the garment.

Hand Feel and Texture: Assess the hand feel and texture of the fabric after desizing. Fabric should be soft and have a desirable texture, indicating the successful removal of sizing materials.

Absence of Stiffness: Confirm that the fabric is free from stiffness, as residual sizing materials can make the garment stiff.

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Color Uniformity: Check for uniform color across the garment after desizing. Inconsistent color may indicate incomplete removal of sizing during desizing process.

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Fabric Weight Stability: Check for consistency of fabric weight on the garments. Significant fabric weight deviations within same garment may indicate inadequate desizing.

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Starch Iodine Test: This test is a common method in textile labs to detect starch-based sizing in garments. ?In which the fabric is spotted or treated with?Iodine solution (Example-potassium iodide), which?reacts with the starch and?produce a bluish-purple-black colour. ?If the fabric turns bluish-purple-black colour, it means there is starch present. If there is no starch the colour may be brownish-yellowish.

This test is used after desizing garments to check if any sizing material remains in the fabric.

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Reporting & Documentation: The results of the desizing process should be reported and documented. This can include generating reports or updating quality control records.

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Feedback and Communication: Any issues or deviations identified during the desizing process should be communicated to the relevant team, such as production or quality control personnel. Timely feedback and communication can help address any process or quality issues. Corrective actions can be taken if necessary.

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Follow-up Actions: Based on the analysis, evaluation, and feedback, appropriate follow-up actions should be taken to address any identified issues or improve the desizing process. This can include process adjustments, equipment maintenance, or training of personnel.

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Non Conformity related to Desizing process

?Here are descriptions of common non-conformities that can occur during the desize wash of denim garments, from a denim wash technical point of view:

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Inadequate Desizing: Inadequate desizing refers to the incomplete removal of the sizing agents applied to the denim fabric during the manufacturing process.

Causes: Inadequate desizing can occur due to insufficient exposure time to desizing chemicals or improper desizing agent concentration.

Prevention and Correction: Ensure the proper concentration of desizing chemicals and sufficient exposure time to completely remove sizing agents. Conduct regular tests to confirm adequate desizing.

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Uneven Desizing: Uneven desizing occurs when some areas of the denim fabric are adequately desized while others still contain sizing agents. This can lead to variations in the fabric's texture and color.

Causes: Uneven desizing can result from irregular chemical application, inconsistent fabric wetting, or uneven distribution in the desizing machine.

Prevention and Correction: Maintain uniform chemical application and fabric wetting. Ensure proper machine loading and agitation to achieve consistent desizing results.

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Residual Desizing Agents: Residual desizing agents refer to the presence of leftover sizing chemicals on the denim fabric even after the desizing process is complete.

Causes: This can occur when desizing chemicals are not adequately rinsed out or neutralized.

Prevention and Correction: Implement thorough rinsing and neutralization steps to remove all traces of desizing agents. Regularly test for the presence of residual chemicals.

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Back Stain: Back staining is the unintended staining of the back side of denim fabric during the desize wash process. It can result in undesirable color variations on the inside of the garment.

Causes: Back staining can occur due to inadequate rinsing, improper stacking of garments in the machine, or the presence of excess desizing chemicals.

Prevention and Correction: Ensure thorough rinsing to remove residual desizing agents. Properly stack garments to prevent contact between fabric surfaces. Maintain clean processing conditions to avoid contamination.

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Inadequate Rinsing: Inadequate rinsing refers to insufficient removal of chemicals, including desizing agents, from the denim fabric.

Causes: This can happen due to a lack of rinsing cycles, inadequate water usage, or improper machine settings.

Prevention and Correction: Implement adequate rinsing cycles with sufficient water flow to remove all chemicals. Adjust machine settings as needed to improve rinsing.

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Over Desizing: Over desizing occurs when the desizing process removes not only the sizing agents but also some of the fabric dye or indigo, resulting in excessive color loss.

Causes: Over desizing can be caused by using overly concentrated desizing chemicals or excessively long desizing cycles.

Prevention and Correction: Carefully control the desizing agent concentration and exposure time to avoid over desizing. Monitor the process to prevent excessive color loss.

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Lack of Process Control: Lack of process control refers to the absence of systematic monitoring and control measures in the desize wash process, which can lead to unpredictable results and inconsistencies.

Causes: Insufficient attention to process parameters, inadequate training, and poor record-keeping can contribute to a lack of control.

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Prevention and Correction: Implement process control measures, including regular monitoring, parameter adjustments, and employee training. Maintain detailed records to track process performance.

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Insufficient Quality Checks: Insufficient quality checks refer to the failure to conduct thorough inspections and tests to ensure that the desizing process meets quality standards.

Causes: This can result from negligence, a lack of defined quality control procedures, or inadequate training of quality control personnel.

Prevention and Correction: Establish clear quality control procedures, conduct regular inspections, and train personnel to recognize and address desizing-related issues promptly.

In conclusion, effective desizing in denim garment production requires meticulous pre-desizing checks, continuous monitoring during desizing, and thorough post-desizing inspections. Addressing common non-conformities through preventive measures, corrective actions, and robust quality control ensures the consistent production of high-quality denim garments.

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