Boil Off in Stretch Woven Finishing

Boil off is a crucial term in the realm of stretch woven fabric wet processing, dyeing, and finishing. It signifies a "relaxed" state of the fabric, typically achieved by boiling or washing the fabric in hot water for about half an hour. This process aims to reach the jamming point of the fabric, where the weft and warp yarns relax to their maximum extent. Originally, the boil off test was designed to reveal the full stretch potential of the fabric. However, in the context of exhaust fabric finishing, it also became a vital reference point for determining the fabric's finished width or heat set width.

The Significance of Boil Off in Fabric Processing

In exhaust dyeing, where the fabric can be relaxed, the boil off width serves as a benchmark. When setting the heat set or finished fabric width, it is recommended not to exceed 10-15% of the boil off width. Exceeding this range can lead to issues such as fabric "growth," poor recovery, or loss of elasticity. Thus, the boil off width helps ensure that the fabric maintains its stretch functionality and performance after finishing.

Continuous Dyeing and Boil Off

For most cotton woven fabrics, the finishing process involves continuous dyeing, which does not allow the fabric the same liberty to relax as in exhaust dyeing. Processes such as chain mercerizing, scouring, and bleaching help relax the fabric gradually. In these cases, having precise data on the boil off width is essential. When determining the heat set width, it is crucial to aim for a width that is 10-15% greater than the boil off width. This careful calibration helps maintain the desired fabric characteristics without compromising its stretch and recovery properties.

High stretch articles and certain weaves, like satin, require additional trials due to their significant relaxation/shrinkage potential.

Denim Finishing and Boil Off

Denim finishing presents a unique case. Unlike other fabrics, denim does not undergo proper heat setting during manufacturing. The finished denim fabric still contains sizing and has the potential to relax further, which occurs during garment washing. For semi-relaxed denim fabrics, achieving high heat-setting efficiency can prematurely kill the stretch potential. Therefore, understanding the boil off width is crucial for denim as well. It indicates whether the fabric construction needs to be adjusted on the loom, such as altering the reed opening or the number of ends per inch, to achieve the desired stretch. In case of denim fabrics boil off width or thoroughly washed fabric (with resizing agent) etc can help also to understand recovery power of fabric, which areas might impact growth, and one very important thing is after washing how would be fabric appearance. In many high stretch denim fabric gets "orange peel" or "elephant skin" effect which makes garment less premium. Such fabric appearance can be avoided by modifying the fabric construction on the loom.

Conclusion

Boil off is an essential aspect of stretch woven fabric processing. It provides a reliable reference point for fabric stretch & setting fabric width. Helping manufacturers achieve the desired stretch, recovery, and overall performance in the final product. Whether in continuous dyeing or exhaust dyeing, understanding and utilizing the boil off width is key to optimizing fabric finishing processes and ensuring high-quality textile products.