First of all, that’s not me. This lovely model is wearing the first garment that I cut and sewed on the bias. What you don’t see are all the mistakes I made and all the tricks I learned in the process. However, I will share all that with you soon enough. But, let’s begin by answering- What is Bias?

Bias refers to the direction that fabric is cut or worn on the body. Think of a square piece of woven fabric. There is a lengthwise grain and a crosswise grain. On a bolt of fabric, the lengthwise grain runs parallel with the selvedge ends (the tightly woven end that does not unravel), and the crosswise grain runs parallel to the part that is cut from a bolt. Bias represents any diagonal that crosses the lengthwise and crosswise grains. Since the bias is not itself a grain line, it creates more stretch than the two grain lines.

In the manufacturing of woven fabric (silk, wool, cotton), yarns attached to the loom are called the warp yarns and are held tautly in place while other yarns are weaved through it. The warp is the lengthwise grain. It is generally considered the stronger of the yarns in a fabric. At each end is a concentration of yarn called the selvedge. The selvedge holds the fabric tighter to the loom making it easier to weave. The yarns that fill in the warp yarns are called weft yarns. They create the crosswise grain of the fabric. Sometimes the crosswise grain is slightly more relaxed than the lengthwise grain.

Most industry patterns for sewing are designed to run directionally along the lengthwise grain because it is considered the stronger of the grains. For instance, a straight skirt pattern is placed on the fabric so that the center front and back of the skirt run parallel with the lengthwise grain. This generally makes for an easier project and uses less fabric, but it can limit style and design elements.

There are some parts in a pattern that naturally get cut on the bias, such as arm holes, neck lines, etc. That is why it is generally stay-stitched (to prevent stretching) before constructing the rest of the garment. Although these areas may intersect the lengthwise and crosswise grains at a diagonal, it is not necessarily cut on the “true bias”.

True Bias occurs at the 45 degree angle of the intersection of the lengthwise and crosswise grains. In other words, if you take the corner of the fabric and fold it into a triangle, the diagonal formed represents the direction of the true bias.

You don’t always have to cut your pattern on the lengthwise grain. Fabrics hang differently on the bias vs. lengthwise and crosswise grains. The images below show the same dress pattern. One was cut with the pattern aligned on the cross grain, and the other the was cut with the pattern aligned on the true bias.

There is a distinct difference in the fit of the two garments. The bias cut garment comfortably wraps around the body while the cross grain is stiffer and hangs on the body. If I had cut the garment on the lengthwise grain, it would have been even less flexible. You couldn’t just slip the garment over your head. It would require a zipper to get in and out of it. This is one of the many benefits of bias garments. It stretches and moves, which means you can often eliminate darts and seam closures such as zippers.

Many people fear sewing on the bias because of this stretch. Managing the stretch in the construction of a bias garment requires more time and care than a lengthwise cut garment. This is why you don’t see many bias sewn garments in ready to wear clothing. However, if you take control of the bias from the beginning and follow simple couture guidelines, you can create a beautifully fitting garment that flows and moves with the body.

In my next posts we will explore what is couture and one of its first principle steps- making a muslin or toile from a pattern.