There are a few different methods of trimming the coat. I will go over them briefly, and you can choose whichever you prefer.
The first is called the bound edge, and was often done in silk, or in wool. Since mine is a more upper class coat, I’ve chosen silk. Cut a piece of silk on the bias, 4 times the desired final width of the trim, plus 1⁄4 inch. This gives you room to get around the edge of the coat, which often has some bulk. In my case, I wanted trim at a final width of 3/8 of an inch, so I cut my silk at 1 3⁄4 inch wide.
Lay the trim right sides together on the outside of the coat. Do a combination of back and running stitch to save time, at the desired depth. Catch only the outside layer of the coat, as the trim will wear away after some time, and this will make replacement easier. A good reason not to use a sewing machine.
Then fold the trim under itself to the other side, and secure with a slip stitch. This gives a nice appearance, and is probably my favourite style of trim.
A piping finish must unfortunately be done as you are constructing a coat, so it is not an option for this present coat.
Begin by cutting some bias strips of light wool. These should be at a 45 degree angle to the selvage, allowing them to stretch easily. Each strip should be 1 1⁄4” wide and long enough for the area you are working on.
Cut out these strips, fold them in half, and press well, so that they retain their shape. The finished piping should be 5/8” in width.
Baste a strip of piping to the right side of your fabric, with the folded edge on the inside, and the raw edges all lined up.
Carefully stitch down the piping, using a half inch seam allowance. This will give you piping that is 1/8 inch wide when finished. This can be tricky to do, so go slowly, turning the wheel by hand if you like. If you make the piping too narrow, it will not be able to fold under, and will disappear from view. If it is too wide, it will look bulky and flap around on the finished coat. Definitely not elegant.
Press the piping to the wrong side, so that only the 1/8” of piping is showing on the outside. At this point, the canvas would be put in, and the raw edge of the piping sewn to it with a cross stitch.
I’ve seen this on a couple of original coats, and the finish is subtle yet striking. From a distance, you can’t really see it, but up close, all of the detail comes out. Take a 1/16th inch silk cord, and simply lay it on the edge of your coat, securing it with invisible stitches as you go. Sorry, no photos due to lack of permission.
Where to put the trim
Trim can go along the front of the coat, the collar, the ends of the sleeves, and along the back vent. It is important for you to study originals, and photographs, so as to get a better idea of how to apply the trim. I will leave that as an exercise for you.
You have finally made it through to the end of this workshop! Hopefully you made it through with little error and confusion, but if not, please ask for some help at the support forum. I’d also love to see photos of your finished pieces!