Let's get to it. The first thing you need to do is finish the side edges that you will be inserting the zipper into. Run each edge through the serger individually, that way you can press the seam open after the zipper is in. (I skipped this step because I was in a huge hurry to finish my top.)
The next step is to sew down from the armhole approximately 2"-3". Here's trick No. 1--Use a seam allowance that is a generous 1/8" larger than the seam allowance you're going to use to sew the zipper in with. I used 1/2" to sew the seam and 3/8" to sew the zipper. The reason why you want to do this is to make a tiny "garage" of sorts for the top of the zipper pull to "park" in. All you'll end up seeing from the right side is the dangle part of the zipper pull.
Place the zipper face up next to the side seam. Unzip the zipper all the way. To position the right side of the zipper with the right side of the fabric, turn the zipper over by twisting it toward the fabric it needs to be right sides with. As you turn the zipper over, the zipper teeth will "wave" to you. ***If you twist the zipper the other way, the zipper teeth will "scratch" the cutting board and you'll sew it in backwards! (As me how I know!) Anyway, I alway envision the zipper teeth waving hello to me as I twist it towards the fabric right sides together, a little whacky, but it works!
Here's a close-up of what an invisible zipper foot looks like. This particular one is my fav...(while I am a Pfaff girl at heart, Bernina rings in with the best invisible zipper foot on the market!) If you don't have an invisible zipper foot in your accessory box, it's very likely that you can get one from your local sewing machine dealer--definitely worth it, no matter what brand of machine you own, they all work great.
Snap it on your machine and select a straight stitch (length = 3.0 mm). The goal is to get the teeth of the zipper into the grove so you can sew close to them.
Starting at the very top of the right side of the zipper, position the zipper under the foot so that you can wiggle the teeth into the groove. ****Many sewers press the zipper teeth flat with an iron--I think that's a throw back from the days of the generic plastic feet that you can still find in the zipper section of the sewing store. If you're working with a brand specific invisible zipper foot like the one pictured above, you don't need to press the teeth flat. The grooves in the foot do a great job positioning the zipper for the needle. If you do press the teeth flat, you might end up sewing too close to the teeth and your zipper won't zip up!
With the teeth sliding through the groove, stitch down the length of your zipper (I'm using a 7" zip.) Stitch until the front of the foot hits the zipper pull (which is unzipped all the way.) Back tack and trim threads.
Here's how the right side looks before it's pressed.
Repeat these steps to sew the left side of the zipper. Make sure that the top of the zipper tape is positioned evenly with the right side.
After the zipper is sewn in you need to switch the invisible zipper foot for the regular zipper foot. Here's what the Bernina zipper foot looks like.
To finish the top of the zipper, position the side seam into your sewing machine so that you can line the needle up with the end of the short side seam that you stitched earlier. The zipper foot should be on the inside of the seam so you can nudge the needle over to the left to line it up with the seam. (We are going to make the "garage" for the top of the zipper pull that I mentioned earlier.) Back tack and continue the seam until it overlaps the top of the zipper seam 1/4", back tack to secure the seam. When you zip up the zipper the top of the pull will pull right into that tiny space, concealing it from view.
Finish the bottom of the seam under the zipper. Position the seam into your sewing machine so you can line the needle up a stitch or two below the end of the seam. ***Trick No. 2--Don't try to line the needle up with the end of the seam exactly...it's too hard to sew straight down from there and you can end up with a bubble or some other unsightly thing. If you start just below the seam, leaving a tiny hole (which you'll never see from the right side), you're much more likely to end up with perfect results.
See, you really can't see where the zipper ends and the seam starts (or the tiny hole for that matter.) When you're done sewing the seam, press the seam allowances open and lightly steam the zipper right side and wrong. (Don't over press by using the weight of the iron...just hover and steam.)
If your first zipper doesn't come out perfect, don't fret...it just takes a little practice. Between you can me I had my good friend Marisa put all my invisible zippers in until the day I met the Bernina invisible zipper foot!
...Yes, I noticed that my piping doesn't exactly match up...I was in a hurry to finish this top for my wedding! (The funny thing is that it was threatening thunder and lightning that day, so I wore something more "wet weather friendly"...Happily, the heavens cooperated with our nuptials and the storm started 5 minutes after we were done with pictures!