Why does knit fabric edge curl and how can it be reduced?

The edges of single jersey roll toward the back of the fabric because the structure has different tensions on face and back. Curling is normal and does not disappear completely. It is reduced by heat-setting at the right temperature, stenter finishing, compacting, and a fabric with more elastane or a denser structure. At cutting, use vacuum tables or weight the edges, and at sewing use tape or double-needle attachment. Ask for swatches that show edge behaviour, especially for fine knits.