Sewing Rule: An Invisible Zipper Is Attached Prior To Sewing The Seam Housing It
One of the most unique aspects of sewing an invisible zipper application is that the zipper is stitched to the seam edges first, after which the rest of the seam is completed.
During the application process, the zipper is kept open and each zipper portion is aligned and stitched individually to each corresponding seam edge. That being said, it is important that the zipper is aligned evenly along both edges- use the seam's top horizontal edge as a guide.
During the application process, the zipper is kept open and each zipper portion is aligned and stitched individually to each corresponding seam edge. That being said, it is important that the zipper is aligned evenly along both edges- use the seam's top horizontal edge as a guide.
Once the zipper is attached, the bottom portion of the seam should remain open while the closed zipper portion should resemble a regular seamline at the top.
To complete the seam housing the invisible zipper, align the bottom seam edges as you would any regular seam: face sides touching and edges aligning. Move the bottom of the zipper tape away from the seam allowance to keep the seam as flat as possible, and insert pins perpendicularly through both seam edge as shown.
Using a zipper foot, align the machine needle as close as you can to the bottom of the existing zipper application stitch. Machine stitch the bottom of the seam at the designated seam allowance (1/2" in the image above). Once you've stitched about 3"-4" inches away from the zipper, switch to a regular zipper foot and stitch the remainder of the seam in a conventional fashion.