After blocking and finishing garment pieces, carefully join the two sections together at top and bottom. I use a length of scrap yarn to tie them together leaving a little gap between each segment for zipper teeth. Experts vary on whether teeth should be left visible or not and to the distance between knitting and teeth. The fuzzier the yarn, the more likely it is to get caught in the teeth. Smooth yarns can be sewn close to the teeth. In the photo samples I've used colour contrast and close up photos so you can see the details.
Carefully align top and bottom edges of knitting. With zipper closed and right side of garment facing, pin zipper in place behind work. Insert straight pins perpendicular to zipper teeth on right side of project. Use contrasting thread to baste in zipper with a long running stitch about ¼ of an inch away from edge of knitting. As you baste pull the tab down, out of your way to ensure stitches at top are not distorted.
|This is my basting thread.|
Test the zippers ability to move freely without eating the yarn, after pinning the zipper in place by opening and closing zipper several times. I have seen a variation where the two pieces are sewn together closely with a basting thread first. I don't recommend this method because of the fuzz factor.
Remove pins and check to make sure zipper lays flat. Check alignment of garment at top and bottom before moving on to permanent stitching. Make any adjustments necessary. Avoid stretching or puckering of the knitting. Work from right side of garment using matching thread and use a back stitch to secure edge of knitting to tape of zipper, one stitch in from the edge of the knitting. Maintain the alignment of back stitches along column of edge stitches. Start as close to bottom of tape as possible.
Separating zippers have a finish on tape at bottom to stop fraying. Sewing needles cannot pierce this finish. Whip stitch zipper tape on outer edge to garment on wrong side. Fold extra tape above teeth under at top between tape and garment tacking it into position. Remove all basting threads.
Finish by steaming area with an iron, without touching iron to work. Pat knitting flat and leave it to cool before moving it. Many references reverse order of sewing edges of tape, which I find makes it more difficult to correct if any puckering is encountered.
Zipper facings are an option if inside edge of zipper will show when garment is unzipped. Hand knit facings can be knit separately and sewn into place or consider using grosgrain ribbon to cover zipper tape. However, most knitters dislike the way a zipper changes the drape of knitted fabric, adding a second layer of knitting as a facing will make finished work both thicker and stiffer. Consider this treatment for knitting techniques which result in less fluid fabrics such as mosaic or modular knitting.