Here is how I finished this sweater, with apologies for the very! bright! orange, my camera has hissy fits over the magenta to orange scale when it’s forced to take pictures indoors at night. I like to wrap the edges of the zipper tape in soft twill, and finish the top of the zipper with the twill — this makes it nicer against the skin on my neck and creates a stop for the top of the zipper at the same time. I sew the zipper in by hand in a pathetically fastidious manner, you can also find excellent directions for sewing a zipper into a sweater over at Chicknits.
Step One: Wash and dry sweater to shrink it about as much as possible.
Step Two: Wash and dry twill tape to shrink as much as possible. This orange twill is hand dyed from Glamscience (also at Etsy) and is fantastically saturated with color. When I washed it I knotted the ends to keep them from fraying and stuck it in a mesh bag with some white socks. The socks were to determine if there would be any bleeding from the dye. The socks emerged completely unscathed. Viva Glamscience! The twill is nice and soft and makes all the difference where the zipper hits the skin on my neck, the sweater is far more wearable for it. Iron the twill when it comes out of the dryer.
Step Three: Determine the length of the zipper. I take tip from Grumperina and sew myself into the sweater, then measure along the center front. This measurement will be shorter than if you lay the sweater flat and measure it that way, and will eliminate any unflattering bubbles you can get from a too-long zipper. Err on the 1/2-an-inch too short side.
Step Four: Cut the zipper. I love two-way separating zippers. They are generally meant for jackets and are a bit chunkier than seems good for a sweater, but the ability to unzip from the bottom great – when you sit it keeps the bottom hem from stretching out. The top-down and bottom-up zipper basically acts like buttons. You can usually find a few colors at fabric stores, and a lot of colors over at Zipperstop.com (click to see a scan of the color cards). I’ve also gotten recommendations for Zipper Connection, which also carries two-way separating zippers. Anyhow, be careful to cut between teeth, and I usually dip the cut ends in some Fray Check, but I wrap the tops in twill so this isn’t strictly necessary.
Step Five: Machine sew the twill over the edge of the zipper. I tucked the edges over the bottom corner and machine stitched it down. I stop near the top with a few backstitches.
Step Six: Hand stitch the twill over the top of the zipper to create a zipper stop and keep it from scratching your neck. This part involves a bit of squinting and swearing, thrive on the frustration!