Q: How do I test water colorfastness on zipper tape?
Water fastness is assessed by immersing the specimen with adjacent fabrics in water, working it under defined conditions, then draining, drying and grading the staining of the adjacent fabrics and the change in the specimen. The result matters most where the zipper sits against a light lining, a pocket bag or a contrasting placket, and where the garment may be worn damp.
Method conditions differ in temperature, time and liquor ratio, so state the method with the grade. The alkaline perspiration test is a useful companion, because sweat is more aggressive than water and is the realistic exposure at a neckline or a waistband. Test the finished tape after any heat setting or re-dyeing, and test the darkest shade in the range.
Acceptance is usually set as a staining grade on each adjacent fibre, commonly 3-4 or better, with the requirement tightened for pale linings. If a result is marginal, check whether the tape was properly rinsed at the dyehouse; poor rinsing is the usual cause of water bleeding and is correctable without changing the shade.