This is an extract from Bag Making Techniques for beginners & beyond by Susan Dunlop. This book teaches you all the techniques you need to either design your own bags, or adapt bag patterns. Find both the paperback and Kindle books on Amazon here.
This tutorial can be used to turn an open top bag into a more secure zip top bag, so you don’t have to worry about the contents of your bag falling out. To make the right size panel for your bag pick a zip the same length as the bag, and make the panels 2 inches shorter.
I used a 38cm (15″) chunky zip as an example for the following instructions. Cut a 6.5cm x 12.5cm (2.5″ x 5″) piece of fabric to make a zip-end tab. Fuse with suitable interfacing.
1 Fold the tab in half widthways, right side together, pin. Stitch the sides with a 1cm (3/8″) seam. Trim across the bottom corners, avoiding the stitching. Turn to right side, pushing corners out. Fold in the raw edges by 1cm (3/8″). Insert the closed end of the zip into tab, pin. Topstitch across tab opening, 3mm (1/8″) from edge and again 5mm (1/4″) from the edge. Topstitch around the other three sides.
2 Fold back the zip tape ends at angles, pin.
3 Cut two main fabric and two lining fabric, zip panel pieces, measuring 8cm x 33cm (3″ x 13″), adjust the length according to the size of zip you’re using. Fold the short ends of all four pieces to the wrong side, by 1cm (3/8″), press. Topstitch with 5mm (1/4″) seams.
4 With both right sides up, align one long edge of the zip along the long edge of one lining piece, with the tab end extending past the short edge. Pin, then hand-baste, or use double-sided basting tape.
5 Lay a main fabric piece on top of the lining, right sides together, so the zip is sandwiched between the layers. Match up all edges, pin, then hand-baste or use double-sided basting tape. Using a zip presser foot, stitch close to the zip teeth.
6 Flip back both the lining and outer, to bring both wrong sides together. Match up all the edges, press and pin. Topstitch close to the edge, near the zip. Topstitch another parallel line of stitching 3mm (1/8″) from the first row.
7 Repeat steps 4 to 6 to sew and topstitch the remaining zip panel pieces to the other long edge of the zip.
8 The zip panel can now be sewn into the main body top edge seams of the bag, during construction. Alternatively, if you’re making a bag which has top band panels (which is the easiest option), sew the zip panel edges between the main body and top band panel seams.
9 Place the zipper panel raw edges along the top edge of a main body lining piece, both right sides up.
10 Lay a top band panel on top, with wrong side up. Pin and sew a 1cm (3/8″) seam.
11 Fold back the top band panel and press. Topstitch 5mm (1/4″) from the seam.
12 Attach the other side of the zipper panel between the other main body lining and top band panel in the same way. This bag will have side and base panels added, see how to add bag bases, side and base panels (pg.30) for instructions.
Note: the zip should be open to continue with the bag construction.
Above is an example of a completed lining bag with the zipper panel installed, before it’s attached to the main outer bag section.