Step 1. Prepare your seam by overlocking each edge and pressing back the 1.5cm seam allowance. Beauty of an invisible zip is it just looks like a seam when it is properly inserted and you can have as little as 10cm seam to apply it.
Step 2. Using a marker or chalk, on both sides of teeth mark a level point on wrong side of zip tape 2.5cm above finished end of teeth.
I use a 20cm zip for an 18cm opening.
Step 3. With zipper opened, place zipper face down onto right side of garment, teeth just in from fold 2mm, pin on outer edge of tape to hold in place for length. Top finished point of zip should sit at the 1.5cm seam allowance. The top pinked edge is usually level with raw edge.
Step 4. Repeat pinning for second side. Sew, using a basting stitch and a regular foot with needle in far left position( or a zipper foot)down each side stopping at blue marked point.
This row holds zip in place for final row, which is much closer to the zip teeth, and is removed later.
Now both sides are tacked in and should look like this…
Step 5. Using an invisible zipper foot ( no. 35 for Bernina) and starting at the top, unfurl zip so that teeth coil lies under left bridge of foot. Stitch in a regular stitch length to bottom marker and reverse a few stitches to hold well.
Repeat for other side swapping to right bridge.
When it is zipped up it should now look like this…very neat!
If yours is showing more zip tape on outside, try to stitch seam again and unfurl zipper ahead of foot, as you feed it under the foot and slightly pushing zipper further under foot and stitching inside previous row.
Now to finish off and sew seam below zipper….
Step 6. Try to link up last stitch on left with last stitch on right with a pin, anchor as best you can, with another pin while this is linked.
Stitch from slightly above last stitching line, holding zipper tails away from seam. It should look like this…
If you have difficulty with this linking up and machining, dont attempt to sew within one or two stitches of where you finished hand stitch using a needle and thread.
Finished zip…nice !
A hook and eye can be placed at top if you want, but I am happy if it looks like this when you bag it out with a facing.