Interlock knitted fabrics are different than your traditional knit fabric. You can tell them apart from regular knitted fabrics as they have the rows, or ribs, of a ‘v’ shape down the face and back of the fabric, making the front and back look the same. This is why interlock is considered a double-faced knit. Essentially, two fabrics are knitted together at the same time on one machine and remain interconnected.
Interlock fabrics are both easy to work with and comfortable to wear. Not only do interlocks have a great amount of stretch, but the fabric has a good recovery. This means that interlock knit fabric will return to its original shape after it has been stretched out. Even though this type of knit is firmer and holds its shape better than a traditional knit, it has little elasticity in the width of the fabric.
Double knits such as interlock are typically used in active wear. Often the bi-layer is knitted with two different fiber yarns. For example, using a staple fiber such as cotton can help to wick away moisture from the skin while the second layer of a synthetic fiber can disperse the moisture so that it evaporates quickly. Stretch fabric technology has come a long way, leading to more comfort than ever before.
A dictionary of textile terms. (14 ed.). New York, NY: Dan River, Inc.