As I was looking through some of my many blouse patterns, I realized that they presented quite a few ways to attach a convertible collar. By convertible, I'm using the vintage term which might be different from contemporary definitions. A convertible collar is a notched collar that can have a button hole in the lower lapel, therefore can be buttoned across the chest. Most of the times when I find this description being used, it simply refers to a notched collar.
I'm in the middle of another 40s blouse, which has this collar treatment. As I was working on it, I decided to look back at the instructions which is something I haven't done in a long time. Apparently I was using a different method of attaching the collar than instructed. I was intrigued and decided to do some mockups to practice my collar sewing skills.
I'm using some red scrap linen and a bright thread to demonstrate. I cut out half collar pieces and two facing pieces meant to mimic the shirt front and the shirt facing.
Looking through my reference I came across three primary ways for sewing the collar. 1) attaching at the notches, 2) I use the most, sewing the sandwiched pieces, and 3) top stitching.
1) Attaching at Notches
This technique is most likely the trickiest. It also requires more exact measuring than the other two. Sew the collar and facing pieces right sides together stopping at the notch. Next, you open the pieces and match each seam at the notch. The reason why I find this way a bit more troubling is that you are actually sewing two different seams, one for each side of the collar pieces.
The seam starts at the notch where all four pieces meet, but the stitching never overlaps.
Slash the curved seam (It's slashing for convex curves and notching for concave curves, right? Well, one of those...) and press open.
The pros of this way are it creates less stress at that joint.
The cons are it requires a lot more precise measuring, and if you are not precise, you can have a gape at that joint (see mine) that you might have to go and correct.
This way is great for thick fabrics or coats because the excess fabric might fill in a slight gape if you have one. Not to worry if you do, you can re-sew that area, or you can hand tack it closed.
2) Sewing Sandwiched Pieces
This is the technique I use most often. I like it because I get to line up the collar and the facing pieces and wrap them completely around the blouse and sew the entire thing in one go.
Matching at notches, sew the collar pieces to corresponding blouse front and facing piece.
At jointing seam, pin pieces into place. Notch at the place where the seam is to intersect. Sew the collar and slash/notch accordingly.
Once it's sewn, you are going to have a bit of bulk from the seam allowance of four pieces of fabric.
When I'm sewing at corners, I back stitch an 'X' so that when I trim that corner, the fabric is reinforced and I don't have to worry about the corner fraying when I turn it right side out.
This technique requires a bit more fussing. Mostly twisting of the joint so the notch lays correctly. Press the heck out of it and you're golden.
The pros are this technique works best with lighter fabrics because of the bulk. Cons are if the notch on the stitching seam is not correct you can get extra bulk and that can really make it difficult for your collar to lay correctly.
3) Top Stitching
I find this the option that most beginners use when sewing a collar like this. Often people who do it this way do it the way I'm going to show, and not the actually more labor intensive way that is much like view 1).
Sew the matching pieces together stopping at marking. Notch at that stopped place and flip the pieces right side out. Press. With the top of collar, turn under seam allowance and place over the the facing. Machine stitch down. This is the wrong way to do it. The lapel is supposed to curve, giving the collar a nice soft roll. That can't happen if both sides of the collar are sewn to one another.
The space between the pieces is what creates that roll. They give off one another, and thats what makes the subtleties of sewing so rewarding.
*The correct way*
You can top stitch the collar in place, simply fold under the seam allowance, sew it like in collar 1), but this time you can sew in one fluid stitch. The pros of this way (the correct way) are it creates a rather bitchin' look if you like top stitching.
Cons are its just a bit more complicated because you are working on the front of the garment so mistakes are going to show more.
So there you have it. Tips I've picked up sewing collars from some of my vintage patterns. Hope it's helped and hope I've outlined everything correctly.