The standard for both ready-to-wear and handmade swimsuits is to sew elastic to the inside, fold it over, and sew another line of stitching to keep it in place. For an alternative, you can add a bit of extra pizzazz to your suit with a contrast edging using one of two different techniques – fabric strips or fold over elastic. Additionally, you can use either technique to get a much cleaner finish on the inside than you can with the traditional technique. Before getting started with this finished edge tutorial, make sure you have read How to Sew Elastic to a Swimsuit.
Note: Both of these techniques increases the size of each finished piece when compared to the traditional way of folding the elastic to the inside. Why is that? You lose 1/4″ from every edge when you fold the elastic to the inside. When you use the fabric strip or FOE you aren’t folding anything to the back so you are effectively gaining 1/4″ on every edge. This might be noticeable when fitting places like the crotch, so if you want to use these techniques and maintain the originally intended sizing, shave off 1/4″ from every edge of your fabric right before applying the elastic.
Fabric Strips: Cut strips of fabric that are 1 1/2″ wide. This is easiest to do quickly an accurately with a long ruler and a rotary cutter. However, if you aren’t perfectly accurate, don’t worry. You will be cutting off the excess of the fabric after it is sewn on.
Sew the fabric, contrast strip, and elastic to each other in a sandwich with the fabric right side up, the contrast strip right side down, and the elastic on top.
Wrap the fabric around the elastic and over to the back. Sew it down using a wide zig-zag or a narrow zig-zag (or straight stretch stitch) on the edge of the elastic, or on the main fabric just to the inside of the elastic.
For a very subtle contrast edge, you can fold the elastic to the back as you would with standard construction. You will be left with a small line of contrast that forms the turn of the cloth around the elastic. Just as if you don’t fold the elastic, you can secure it by a wide zig-zag or a narrow zig zag on the far edge.
For either edging, trim off the excess fabric on the wrong side.
You can use this technique using the same strip fabric as your main fabric if you want a very nice clean edge on the inside that is hard to get using the standard technique.
Fold Over Elastic (FOE): Using FOE elastic on your swimsuit is just like using it on any other project. You do want to note that a swimsuit finished with FOE is best used for sunbathing or ocean swimming as the chemicals used in most pools will break down the elastic. To sew it on to the edge of your swimsuit, align the edge of your suit with the middle crease in the elastic with the inside of the suit against the wrong side of the elastic and sew.
Fold the elastic along its center crease to the right side of the suit and sew another line of stitching to secure it in place.