Sewing shift tests are applied to sewn woven fabrics. Sewing shift is the opening seen in the yarns forming the fabric in the sewing region and extending parallel to the seam by the warp and weft threads sliding over each other with a certain physical effect. This deteriorates the appearance and quality of the fabric. Moreover, the service life of the fabric is shortened.

By means of sewing slip tests, the shear strength of the warp threads on the warp or the warp threads on the weft is determined during a standard sewing of the fabrics. The results of the test will show whether there is a thread break in the fabric due to stitch breaks, fabric breaks or stitches.

For physical tests performed in laboratories, many standards published by domestic and foreign organizations are complied with. In this context, the standards which are taken as basis in the tests of seam slip are as follows:

• TS EN ISO 13936-1 Textile - Determination of shear strength of yarns in woven textile products - Sewing method - Part 1
• TS EN ISO 13936-2 Textile - Determination of shear strength of yarns in woven textile products - Sewing method - Part 2
• TS EN ISO 13936-3 Textile - Determination of the shear strength of yarns in woven textile products - Part 3: Needle fastening method
• TS EN ISO 13935-1 Textile - Stitching properties of fabrics and finished textile articles - Part 1: Determination of the maximum force for seam break using the ribbon method
• TS EN ISO 13935-2 Textile - Stitching properties of fabrics and ready-made textile articles - Part 2: Determination of the maximum force for seam breaking using the clutch method
• BS 3320 Method for determination of shear resistance of yarns in woven fabrics: Sewing method
• ASTM D 434 standard test method for yarn slip resistance in woven fabrics using a standard seam
• ASTM D 4034 Standard test method for resistance to yarn slippage in woven upholstery fabrics