Biased, in the wrong direction

For a number of years now, I've paid fairly close attention to grain line in woven fabrics, much more so than when I first started sewing. It's interesting to me that cross-wise grain is different (and more stretchy) than length-wise grain. Today I had a tiny ah-ha moment when I realized that bias actually has two very different directions.

I began to consider this as I wore and enjoyed my most recent Chateau jacket, constructed from a thrifted bedspread. Although each front piece was cut on the same length-wise grain line, the neckline twisted in two different directions. Now that I look back I can see the twisting beginning right after I finished it.

You can just barely see the torque. The left side of the picture shows the corner turning under and the right side shows the corner turning out. Over time it became more pronounced and so it bugged me more. No amount of pressing and steam-setting eliminated the torque.

The neck edge is of course finished with bias binding. So I wondered - was it the bias-binding that was causing the torque? Of course the answer is yes. I tried to draw a picture to help understand how the bias created asymmetry in the front closure. Bias loves to twist and this is how I visualize it twisting in the original neckline.

So I recut the bias-binding. This time I put a seam in the center back of the bias binding. This allowed me to flip one bias piece to mirror the other in terms of the way it wants to twist.

Voila! Mystery solved.

Just for fun, I added a knot at each corner.

I am so easily entertained.