Cotton Interlock

Cotton interlock is a double-knit made by interlocking two rib-knit fabrics back to back, so the loops of one layer sit inside the loops of the other. The result is a knit that looks the same on both faces, with fine vertical lines and no visible purl side, unlike single jersey which shows loops on the front and purls on the back. Weights run from about 180 g/m² to 260 g/m², heavier and thicker than most jersey, and the interlocked structure makes it more stable and less inclined to run or ladder when a stitch breaks.

The defining practical difference from jersey is that interlock edges do not curl. Single jersey rolls at every cut edge and fights you at the machine, while interlock lies flat, which makes it far easier to cut accurately, pin, and feed. It has two-way stretch across the width with little lengthwise give, so lay patterns with the main stretch going around the body. It has good recovery and holds its shape at necklines and cuffs without the sag jersey can develop. Press with a warm iron, not hot, to avoid glazing the surface.

Interlock goes into t-shirts, baby and toddler clothes, dresses, and anything that wants a knit's comfort with more body and stability than jersey gives. Sew it with a ballpoint needle and a stretch stitch or a narrow zigzag so the seam gives with the cloth, and finish edges on an overlock if you have one. Its flat, stable hand makes it one of the easier knits to start on.