I was recently at a customer site setting up some textile methods. One of them was for ASTM 1683 that is about seam strength and seam integrity. Seam slippage happens when under a certain load the warp and weft threads of a sewn seam start pulling away before fabric itself ruptures. As the load is increased the slippage increases until the fabric or the thread yarn fail. A measure of the seam slippage is the load required to produce a certain amount of slippage or seam opening. In a tensile test of a seam specimen, a part of the energy is used up in stretching the fabric and part of it is causes seam slippage. To determine purely seam integrity we need to "subtract" the effect of fabric stretching. This is why we test a fabric specimen without seam and a specimen with seam to do this "subtraction". Bluehill has a seam slippage calculation that makes it very easy to do this. Here is how to use it.