The fabric for my coat is a heavy wool, after pressing the seams open, they don’t stay flat. I thought of handstitching them down, when another solution came to my mind. On the Threads dvd Sewing techniques Louise Cutting shows a method to hem a garment with two layers of fusible interfacing. This week I was reminded to this technique by my friend Valerie, who showed me the skirt she made in real life. She used this technique for the hem. I interpreted it for use in the seams of my coat.
Two layers of interfacing, fusible side on the outside, stitched with long lines of straight stitches (only for convenience, you could do it one at a time)
Cut strips of the interfacing, close to the stitching line, and as wide as the seam or a little less.
Put a strip under the seam allowance, with the stitched line on the outside.
Press the seam allowance.
After pressing, the seam remains flat.
Tip: I have mainly straight seams on my coat and used the interfacing straight of grain. If you have curved seams, make strips of fusible interfacing from a piece of interfacing that is cut on the bias. Then you will be able to follow the curve better.
As said, you could use the same technique to hem a garment.
And answers to questions: the fabric of the piping is a kind of black velvet, the only fabric in the right kind of black that was not too thick. In the meantime I’ve made another example with a narrower buttonhole. And I’ll be playing with fabric straight of grain and on the bias. The tabs will be on the bias, while the sleeves are straight of grain for example.