Oh lordy, I've falled in lust with silk dupion. What a dreamy fabric to work with! I found a turquoise silk dupion that matches fabulously with the shell fabric of my coat, and I'm going to use it to make a contrast trim around the edges, similar to this St. John Jacket:
After a trialling a few different ways of doing this, I settled on the simple bias binding treatment. To reduce the bulk the seam from the collar, I turned the collar inside out, chopped off the sewn seam and seam allowance, turned it around the right way and overlocked the two collar pieces together.
Sewing bias binding is pretty easy when you've got a straight or curved fabric edge, but it gets a little tricky when you get to the corners! On pre-bought bias binding, one side will be shorter than the other - this shorter side is sewn onto the right side of the fabric, so when the bias is folded over, you can sew 'in the ditch' on the right side and catch the bias folded over onto the backside, like in this cross-sectional diagram:
To get a 'mitred' corner like the one in the picture at the top, you sew along (with your bias pinned to the right side of the fabric) and stop the width of the seam allowance before the edge of the fabric:
You then fold the loose bias strip down so the fold line makes a 45 degree angle to the corner:
You then fold the tail over on itself and pin in place along the second edge:
Starting from the point where you left off (the distance of your seam allowance from the edge), continue sewing along: