Aqueous Extract
Chinese national testing standards specify aqueous extraction protocols to determine the pH value of water extract from textile materials. Testing compliance under GB/T 7573 evaluates chemical processing residues remaining on fibers, yarns and fabrics destined for consumer markets. Neutral pH values close to skin surface levels prevent skin irritation and confirm thorough washing after bleaching, dyeing and wet finishing processes.
Shaking Protocol
Textile swatches undergo mechanical shaking in distilled or deionized water at ambient temperature for two hours to dissolve soluble chemical residues. Glass combined pH electrodes measure the decanted extract solution without prior filtration to prevent ion absorption on filter media.
Customs Compliance
Garment importers shipping goods into Chinese commercial distribution channels mandate certified laboratory test reports under this standard. Un-neutralized acid residues from carbonization or alkali residues from mercerization trigger commercial rejection at port customs or buyer quality control checkpoints. Mill quality management systems conduct routine pH extraction testing on finished fabric rolls before garment cutting and final packaging.
Re-washing or chemical neutralization steps must occur if test values fall outside target limits between 4.0 and 7.5 for direct skin contact items.
Soluble Assessment
Test results reflect water-soluble acidic or basic substances rather than total chemical content bound within the fiber matrix. Sample preparation errors, such as handling fabric with un-gloved hands, contaminate extracts and skew pH readings. Ambient atmospheric carbon dioxide absorption during extended shaking alters water pH if extraction vessels remain un-sealed.
