In order to learn how to make bias binding, it is helpful to know a little about fabric itself. Fabric is made up of woven threads running up and down the length of the fabric (straight grain) and across the width of the fabric (cross grain). These are at right angles to each other. When we cut a square the edges of the square all run in line with either the straight grain or the cross grain threads.
However when we cut a triangle only two at most of the edges run with the grain. The third edge runs diagonally and so cuts across the grain of the grain of the fabric. This is known as being cut on the bias and that edge is more likely to stretch than the other two because there is more give in fabric cut on the bias.
When piecing a quilt, that is something to be aware of and to take extra special care with. Sometimes, though, that extra give can be really useful and cutting binding on the bias can give the binding the extra flexibility to cope with curves or irregular shapes.
Making the bias binding
I have used half a yard of fabric to demonstrate – approximately 18″ by 42″ – and folded it in half. It doesn’t matter whether right sides or wrong sides are together. Fold the bottom left hand corner up to the top edge as shown.
The diagonal fold is along the bias. Place your ruler just inside the fold and cut the fold off so that you have two separate pieces of fabric.
Move your ruler along the fabric so that the 2.1/2″ line of your ruler runs along the edge that you have just cut.
Cut along the edge of the ruler and you have created a strip of 2.1/2″ binding cut on the bias. This first cut creates a strip of bias binding about 25″ long. The next strip will be shorter as you move further along the triangle. Join the strips as for normal quilt binding by placing the ends of the strips at right angles and sewing across the diagonal.
If you need a large amount of bias binding, you may be interested in the continuous bias binding method.