Woven Fabrics. When you think of fabric, you usually picture a woven fabric, which is constructed on a loom. The loom is first loaded with warp yarns (they’re called yarns, even though they’re usually thinner than sewing thread). These yarns become the lengthwise grain (straight grain) of the fabric. They have to be strong enough to withstand being stretched and pulled back and forth. Then weft, or filling, yarns are woven over and under the warp yarns.
These yarns form the cross grain of the fabric. They are typically not as strong as the warp yarns and have a little stretch to them. No matter what printing method you’re using, you want to make sure the print is on grain, not skewed relative to the warp or weft threads. When sewists cut out fabric, especially for garments, they are careful to cut fabrics on grain; otherwise, the garment doesn’t hang correctly on the wearer’s body.
Grain is also important for knit fabrics, even though they don’t have a warp and weft. The bias is an imagined line that runs diagonally across the fabric. Fabric cut on the bias (the “true bias” is 45°) is very stretchy. Cutting on the bias can be useful for making trim that goes around corners and curves or for making garments that drape and swirl. The selvage is formed along the edges of the fabric, where the weft yarns turn to travel back across the warp. This area is woven more tightly than the main body of the fabric for stability throughout the manufacturing process.
A fabric’s identifying information is printed on the selvage. Lately, quilters have had fun using selvage strips in scrappy patchwork projects, and designers have responded by making the selvages just as beautiful as the fabric’s main print.
Understanding the three basic weaves and their variations is the key to understanding the differences among fabrics. The weave determines surface texture and sheen and contributes to strength, drape, and other factors.
Plain weave is the most basic type. Each weft yarn travels over and then under adjacent warp yarns. This fabric tears and wrinkles easily, but it provides an excellent base for printing.
Twill weave refers to any of a number of variations in which each weft yarn travels over two or more warp yarns and then passes under the warp yarns. The pattern is staggered for each weft yarn, creating distinct diagonal lines on the finished fabric. Herringbone and houndstooth are variations of the basic twill weave. Twills are very strong and difficult to rip.
Satin weave is a type in which either the warp or weft yarns are the “face,” floating over four or more of the opposite yarns before passing under one, and then floating over four or more and then under one again. Unlike twills, the intersections do not form a diagonal pattern. The satin weave yields a very lustrous surface and is also highly tear-resistant.