Two Ways To Finish Exposed Separating Zippers
In dressmaking, there are two main techniques for finishing exposed separating zippers. The choice should be made based on garment design, fabric and whether the resulting finish is casual or more tailored.
The simpler, faster and more casual of the two techniques is a topstitched finish. once the separating zipper is stitched to each garment opening edge, the zipper tape is aligned in its finished position toward the garment's wrong side and topstitched along the garment's folded edge. It is up to you how close to the folded edge your topstitching, as long the zipper tape underneath is securely caught by the stitch.
While this finish does not fully enclose the zipper tape on the wrong side of the garment, it does keep the zipper permanently in position, preventing the zipper tape from rolling to the outside of the garment. Visually, a topstitched separating zipper is considered a more casual, sporty look often used with casual jackets, coats, and open-front cardigans/sweatshirts.
A more tailored option for finishing an exposed separating zipper is by using a facing. Given that separating zippers are conventionally added at the garment's front opening, the front-combination facing used to clean-finish the zipper closure is also used to simultaneously finish the garment's neckline. In the construction process, the separating zipper is first stitched to each corresponding edged after which the facing is aligned to the garment opening with face side touching, sandwiching the zipper tape in between the two layers.
In the finished application, the zipper is full hidden by the facing layer and no topstitching is visible on the face of the garment- quite opposite to the topstitched technique above. A faced separating zipper finish is more a more formal, tailored technique which is often used with blazers, coats and tailored jackets.