“Bias” is more than just a personal inclination. It also happens to refer to a handy fabric cutting technique. If you sewn for a while, you’ve probably encountered the term “cut on the bias,” but you may not know why fabric should to be cut this way. In this post, we’ll talk about why bias-cut fabric is a helpful thing, and show you how to do it.
Fabric that has a bias
Technically, the “bias” of a fabric is 45 degrees from the horizontal or vertical weave of the fabric. It forms an imaginary diagonal line across the fabric, like the hypotenuse of a right-angled triangle.
When fabric is cut along this diagonal line, the horizontal and vertical threads are much shorter and can’t pull tightly across the fabric. In short, it makes the weave of the fabric much looser, and most importantly, more stretchy.
Why is bias-cut useful?
Because bias-cut fabric stretches more easily than it’s “square” cut counterpart, strips of bias-cut fabric are commonly used as a binding to finish edges. These strips can be smoothly stretched along the tight curves or odd corners found along the edges of a garment to help give the piece a final, finished look.
The stretchy powers of bias-cut fabric can also be used to change the way a fabric hangs in a garment. For example, cutting on the bias can boost a fabric’s curve-hugging ability to make a sexy, old-Hollywood style gown. The added stretch can also give the draped fabric more weight and a different flow, and help it pool or bunch beautifully, as Ms. Lombard’s gown demonstrates. Less glamourously, bias-cut fabric is how stockings (and jaunty Renaissance leggings) were given their stretch long before the invention of elastic. So, all you Larpers out there, you can use this technique too!
Now that we’ve explained what the basics of why bias-cut fabric is useful, let’s show you how to cut a pattern on the bias.
How to cut a pattern on the bias
When cutting out the pieces of your pattern, you normally align them parallel to the edge of your fabric, like so:
To cut on the bias, you simply need to rotate the pattern 45 degrees. There’s a snazzy trick to help you get the right angle, if you don’t mind messing with your pattern piece.
Take your pattern, and draw a line perpendicular to the handy-dandy provided “grain” line to form an x/y axis. Fold the pattern at 45 degrees so that the two arms of x and y axes line up. (Not a typo. “Axes” is the plural of “axis”. I checked.) This fold is your new, “bias line” for your pattern piece. Align the bias line (pictured in blue) with the edge of your fabric. You can use a measuring tape to make sure that this bias line of your pattern is perfectly parallel to the edge of your fabric.
Keep in mind that there are different rotations that you can create with this trick. This matters if your fabric has a distinct pattern, like stripes. If you aren’t careful, you’ll end up with one pattern piece with stripes slanting leftward, and one with stripes slanting rightward. Just take it slowly, and think before you cut.
HEY! HEY! LISTEN: Because bias-cut fabric loosens the weave of the material, add an inch to all edges of the pattern. The looser weave of the bias will change the fit of the finished garment to be more snug, so give yourself a little wiggle room to work with.