If you pick up a piece of fabric, you can stretch it in three ways, vertically, horizontally, and diagonally. This diagonal stretch is the stretchiest and is the bias of the quilt. You may need a cut of bias for hems, bindings, or may have a pattern that calls for this special stretch. But cutting the bias may be something new to you.
The Dutch Label Shop is where I get my special labels for the backs of my quilts. I love the quality of the labels and the way they look on my quilts. In addition to making a great product, they periodically blog about important things sewers should know. One of the blogs they ran was how to cut on the bias.
First, you have to understand two other fabric terms: selvage and grain.
WHAT IS SELVAGE
Selvage is the name given to the self-finished edges of a piece of fabric. It keeps the fabric from unravelling and fraying. Often it serves the further purpose of providing information about the producer and designer, information that is printed directly onto the unpatterned area.
When a fabric store associate pulls down a bolt, rolls it out on their cutting table, and cuts you a portion of it, they will always cut perpendicular to the selvage. Each piece of fabric will therefore have two self-finished edges, top and bottom.
WHAT IS GRAIN
Just like wood or meat, fabric has a grain. In reference to fabric, the term “grain” indicates the way the fabric is knit or woven together. Take a close look at any piece of fabric. You will notice threads running parallel and perpendicular to the selvage. This is the grain of the fabric. Take your hands and place them on a perpendicular line and try pulling the fabric. There will be no give. Do the same on a parallel line. Again, the fabric will not stretch. Cutting along a parallel or perpendicular line is cutting “with the grain.”
WHAT IS BIAS
Now, back to bias. Take your hands and place them on the opposite selvage, diagonally across from each other, and pull. The fabric stretches! This is because you are pulling along the bias, against the grain. When a pattern calls for a bias cut, it is to take advantage of this stretchy quality. Bias is the thread line which cuts the grain at a 45 degree angle.
HOW TO CUT ON THE BIAS
To easily measure this 45 degree angle, take the top corner of your fabric and fold it down to the bottom edge of the fabric, creating a diagonal fold. Cut along the fold, and voila! You’ve cut on the bias.