The ubiquitous zipper that opens and closes our garments, mostly effortlessly, has a long history dating back to the 1850s. Today, our zippers can be of many types: coil, invisible, open-ended and made of metal or plastic. Zippers can be applied to a garment in many ways.
Centered zippers are visible on the outside of a garment or sewing project and centered on a seam, usually a front or back seam. The zipper itself can be concealed under two equal flaps of the seam, or deliberately made visible as a design element, still centered on the seam. Centered zippers are used in casual wear clothing, for sports wear, and for heavy outer fabrics. Prior to applying the zipper, the seam is stitched or basted closed, usually using a long stitch length, the zipper is centered, with the zipper closed, on the inside seam with the coils along the seam line and then stitched, usually about 1/4" away from the center coils on either side. The stitches from the seam are then removed from the outside to allow for exposing the now centered zipper.
Lapped zippers have only one stitching line visible on the outside of the garment. There is only one flap that covers the zipper as seen from the outside. The lapped zipper is sewn into the garment with the seam basted closed through the zipper area. Pants and skirts most often will use a lapped zipper application.
Invisible zippers are so called because when zipped closed, the seam line closes along with the zipper, enveloping the zipper completely within the inside seam. Only the seam line itself is seen from the outside. The invisible zipper is often used in evening wear, as a deign element or anywhere the zipper would be seen as a distraction.
Before machine sewing the zipper, try any one of the following techniques for the best success:
Double sided invisible tape can be used to temporarily hold a zipper in place before machine or hand stitching.
First pin the zipper to hold it in place, then baste with hand stitching before machine sewing.
The zipper can be inserted manually using a 'hand pick' technique that uses tiny back-stitches or a prick stitch worked from the right side of the garment. Often a couture technique or used for delicate fabrics and for inserting specialty rhinestone zippers.
Use a strip of light-weight interfacing placed between the seam allowances before inserting the zipper as it adds to the zipper's support and minimizes any stitch rippling effect once machine stitched.
When machine stitching, stitch from the bottom of the zipper to the top of the garment edge on both sides of the zipper.
All sewing machines come with a zipper foot attachment for use with traditional centered or lapped zipper applications. The invisible zipper requires a special invisible zipper foot purchased separately. Often the inexpensive invisible zipper foot comes with a variety of shank lengths so that the foot will fit a variety of sewing machine styles.
For an excellent tutorial on how to add zippers, visit:
Tauton Press' Threads Sewing In a Zipper
Sew happy, sew well.