Invisible Zippers, in the right circumstances, are just about the easiest zippers to install. There are a number of YouTube videos that show the basic installation step by step. Collette Patterns has a very good one that can be seen here . After you have mastered the basics, there are a few things to remember that will help to make the zipper truly invisible, (some aren’t).
A narrow strip of iron on interfacing along the stitching line for the zipper tape will help to stabilize knits and loosely woven fabrics. The one pictured below is about an inch wide and runs a couple of inches longer than the zipper.
Press the fabric, lightly steaming both sides, so the two sides that will be joined by the zipper are exactly the same length. This garment is made of medium weight rayon ponte knit, but the method for knits and wovens is the same. It is advisable to finish a woven fabric that frays by binding, serging or zigzaging the edge of the fabric before you start to work on the zipper.
With the invisible zipper foot on your machine, sew the zipper to the fabric as shown in the video. With the first line of stitching you shouldn’t worry too much about how close your stitches are to the zipper teeth. This step is more about getting the zipper anchored to the fabric without distorting the fabric or the zipper. The zipper should lay flat when it is closed and the fabric edges should be the same length at the top and bottom with the zipper closed. After the the first line of stitching the zipper will probably look like this when it is closed.
As you can see, it’s not invisible yet. If there is anything to correct about the position of the zipper, now is the time to fix it. On the example above, the crosswise seams match exactly, but if they didn’t that should be corrected now. To make the zipper invisible simply sew successive rows of stitching closer to the zipper coil. If the first row still allows the zipper tape to peek through when the zipper is closed, just repeat another stitch line little closer to the zipper coil. There is no need to rip anything out.
It’s often only the width of the needle that takes the installation from what you see above to the invisible result below.
In the photo above, the vertical seam is the zipper and the horizontal seam is at the waist. The seam below the zipper is still unsewn at this point. The last couple of inches of the zipper should be left unattached to the fabric making it easier easier to move the zipper out of the way when stitching the balance of the seam. This will also help the end of the zipper to lay flat and the transition from the zipper opening to the finished seam will also be invisible. At this point it works best to install a regular zipper foot to finish the seam.
It’s hard to see in this photo, but I am inserting the needle just beside the zipper stitching. The end of the zipper is barely visible on the left side of the photo. The finished zipper and the finished seam should look like this.
A good tip for matching horizontal seams at the waist or on a yoke, is to sew one side and then match the horizontal seam exactly, pin it and anchor it, by sewing an inch or so on either side of the horizontal seam, before sewing the full length of the zipper tape in place….not so much ripping if you don’t get it exactly right. The picture below shows both horizontal seams matched this way before the zipper is installed. It works just as well to attached one full side and then just match and tack the opposing side.
Stitching the crosswise seam with those few stitches to hold it in place makes the biggest difference in this type of installation. I have tried to just pin and sew, but the fabric always shifts just a little bit. Even a 16th of an inch one way or the other is a glaring mismatch. I work on an old White sewing machine and some of the shifting of the fabric to the zipper tape may not be a problem with a newer machine – I don’t know for sure – but his method works for me every time.
I don’t get to see a lot of couture garments up-close, but I am pretty sure you won’t see invisible zippers in actual couture. However, you will find them, but shouldn’t see them, in everything from very high end RTW to “wear once and throw away” fast fashion. They are easy to install and inexpensive too. With a bit of extra time and attention to the details, anyone can do a good job.