Invisible zippers are different than regular zippers and require a few special considerations. Most importantly, you need a Concealed Zipper foot. That link takes you to the Janome version of this foot. I strongly recommend you go to your local dealer and get the specific foot designed for your machine. This is an optional foot for any machine I've ever come across.

There are plastic versions made to be universal to all machines, and these are quite inexpensive (I show you one below and provide a few links for where to find them online). But ... a ‘real' concealed zipper foot does not cost much more and is a better way to go.

When shopping for your zipper, get one a few inches longer than your actual opening. The color is less important than with regular zippers, because only the little pull tab will show when it's finished.

Unlike a regular zipper, do NOT stitch any part of the seam before you put in this type of zipper. No basting, no partial stitching of the seam.

Some people like to finish the raw edges of the fabric to which the zipper will attach. This helps keep the raw edges from fraying and creating little wispy threads that could get caught in your zipper's teeth. I do this sometimes; other times, I cut my fabric to use the selvedges for my 'raw' edges because selvedges don't fray.

Follow the instructions on the package your zipper comes in. I could just stop here ... but we all know how scary it is to follow the directions that actually come with a product! On we go.

1. Open the zipper (unzip it).
2. Place the open zipper face down on your ironing board.
3. Set your iron on ‘synthetic' or simply a low setting, and iron the zipper coils flat. You want to be able to see the double rows of stitching that hold the coil to the tape. I know, pressing it flat seems weird, but it is necessary. The back of the zipper teeth curl, this is what makes the zipper invisible, but if you leave the curl, you simply won't be able to stitch close enough to the teeth, so you need to press the teeth flat. Don't worry, as long as you don't melt them, the teeth will curl back up when you zip it closed again. And .... with your iron on low, you really can't melt the coil.
4. With the zipper completely open, pin the right side of the zipper to the right side of the fabric. The zipper coil should be on the seam line (½" from the raw edge), and the top and bottom stops should be about 1½" from each cut edge of the fabric. Because the zipper is open all the way, you can pin both sides at once. You don't have to. You can also pin and stitch one side, then go back and pin and stitch the other side.
   
   NOTE: Positioning this type of zipper might seem like a brain teaser, but just try to remember to keep the zipper and the fabric right sides together with the zipper coils running along the seamlines. The reason you leave 1½" on either end, is because I'm assuming this is a zipper in a home décor project – most likely within the side seam on a pillow or cushion. You don't want your zipper to start or end right in the corner. That would make it hard to open and close and it just wouldn't look right. A good rule of thumb is to have the start and end points at least 1" from each finished corner. If you're using ½" seams, that means you need the start point 1½" from the top raw edge and you'll make your stop point 1½" from the bottom raw edge. Now, if you're making a jumbo pillow or cushion, with a side seam that is larger than any standard invisible zippers you can find; it's okay ... you can still use one. Simply increase the distance from the top and bottom stops to the corners. It might need to be 2½" or even more.
   
5. With the right groove of the foot over the coil, stitch down from the top until the foot touches the zipper pull, removing the pins as you go. The zipper foot will not allow you to go all the way to the end. Back tack or lock stitch to secure.
   
6. Place the opposite side of the zipper under the needle. With the left groove of the foot over this side's coil, sew until the foot touches the zipper pull. It's important to stitch BOTH sides of the zipper from the TOP down. If there is any shifting as you sew along the length of the zipper any excess fabric can be trimmed off at the bottom. The start points need to match!
   
7. When you're finished and you lay your zipper flat, it will almost appear to be twisted at the bottom. It's not. You can zip it closed to check if you don't believe me. The zipper curves in on itself, straightens out, and disappears.
   
   
8. Now that the zipper is in place, you have to close the ends so there isn't a gap between the zipper and the seam.
9. To stitch the reminder of the seam, close the zipper. Change from the concealed zipper foot to a regular zipper foot. Adjust the zipper foot to the left position. Lower the needle carefully and get as close as possible to the last stitch you made with the concealed zipper foot. Sew past the remainder of the zipper and along the seam line for about 2".
   
10. If you seam continues for quite a ways beyond the zipper (like a lot more than the 2" mentioned above), you can stop and change to a regular presser foot to finish the seam.
    NOTE: This is more likely to be the case in garment sewing than in home décor. For zippers in pillows and cushions (the most common usage), your zipper is most often nearly the length of your seam.
11. If your zipper is longer than you need, simply make a few hand stitches around the zipper teeth to create a stop where you want your end point to be, and trim off the excess zipper so it does not continue into your seam allowance.
12. If you pull across the zipper you can see the transition from the zipper to the seam. But in normal use, the zipper tape and coils are completely hidden.
    
    

Here's what a generic plastic zipper foot looks like.

It slides all the way over, so you can actual use this same foot to finish your seam rather than changing to a regular zipper foot (as mentioned above in step 9).

YKK and Coats and Clark and Dritz all make plastic feet. We found options online at:

Jo-Ann

Nancy's Notions

Create For Less