Interfacing is so important for Opium that it gets its own cutting layout in the booklet, and several steps in the instructions are dedicated solely to preparing the pieces. It is absolutely critical not to skip these steps: without interfacing, your coat would be completely slouchy and shapeless. It would be too bad to spend so much time on a garment only to be disappointed with the end result!
With Opium, we wanted to design a coat that would be accessible to outerwear newbies. To do so, we swapped traditional tailoring techniques, which are mainly done through handstitching, for modern techniques using iron-on interfacing. The latter serves several roles in the construction of the coat:
Just as with any sewing project, it is important to pick an interfacing that matches the weight of your main fabric. Here, you’ll need an interfacing for midweight fabrics for coats and jackets. You’ll get the best results with a woven interfacing instead of a non-woven. Pellon SF101 Shape-Flex or Vlieseline/Vilene G740 would be great for instance.
For an even more professional result, you can also use weft interfacing, such as Pellon 860F Ultra Weft or Vlieseline/Vilene H410. This is a woven interfacing that includes stronger threads running along the grainline, which add even more stability. Be particularly careful to respect the grainline when you cut this type of interfacing, including for the hem reinforcements!
Iron-on seam tape is used to reinforce the roll line of the lapel and the raglan seams, which are in the bias, so that they don’t stretch over time due to the weight of the coat. It also helps the lapel roll properly! By stretching the tape slightly while applying it, you’re contracting the fabric a little, which helps and maintains the roll: this is equivalent to the traditional tailoring technique which uses regular stay tape, but without all the handsewing 😉
You can find ready-made seam tape online or in stores from brands like Dritz or Collins, under the names fusible stay tape or seam tape. In Europe, Vlieseline/Vilene offers several types of tape that work for Opium: their seam tape, which is a simple interfacing tape, and their bias tape, which has a chainstitch running down the middle for more support.
You can also make it youself, which is just as easy and often much cheaper! To do so, simply cut 3/4” wide strips along the straight grain in your interfacing (the same one you’re using for the coat). Measure the length of the lapel fold line and the length of the raglan seams to know how much tape you’ll need.