Jersey curls because the stitches on the face and the back are not balanced: at a cut edge, the lengthwise edges tend to roll toward the back and the crosswise edges toward the face. The tension in the stitches differs between the two sides, so the edge rolls. Interlock and rib are balanced and stay flat.
Curling is normal and not a defect. It can be controlled by heat setting and finishing. When cutting, use tables with fixing, paper between the layers or vacuum cutting. Sew with light pressing or tape that holds the edge.
curlingsingle jersey
