Though they go through various finishing processes, of which mercerization/sanforization are common, fabrics can still shrink. Â The "dimensional stability" of most quality cotton-based fabrics is minimal, no more than 2-3%. Linen is a different story as most linen fabrics are not mercerized/sanforized. Â Mercerized linen is extremely rare, but it's out there. Thread undergoes various treatments to prevent shrinkage of any significance. Washing and ironing fabric prior to cutting can help to minimize puckering. Â The shirtmaker should also consider which needle to use, the thread type, the thread tension, how many stitches per inch etc on a case by case basis according to the fabric being used. Some shirtmakers even wash interlining before cutting. Double-needle seams are generally much wider than single-needle seams, and sewn with fewer stitches per inch. Â You could say that the fabric which is packed into a double-needle seam has more room to shift around than the fabric packed into a single-needle seam.