Learning how to sew is a lifelong process, I am, and will, always be picking up little tips and tricks to make my garments have a professional feel to them. This is one one my favorite tricks that I learned in my bridal wear sewing class at BYU-I. One of the other students who will forever stand out as a kindred spirit, and who I look up to as a mentor, taught me this wonderful method for hemming fine fabrics.
Step one: chiffon has a tendency to warp and fray very easily, and as a result you must work carefully, with the goal of making your edges appear something like the edge I've shown below. Some additional trimming may be necessary before you begin.
Step two: Put your chiffon under the presser foot, folded over about 1/8", DO NOT use pins to hold your fabric in place as this will slow you down and actually make it harder to get a clean edge.
(if the picture below is confusing, keep reading it will make more sense as you go)
|This is the wrong side or back of the fabric|
|This side is the right side, the side that will be visible after the garment is finished|
|This is what the outside or right side of your finished garment will look like.|
|This is what the inside or wrong side should look like, you will be able to see both sets of stitching.|
*For clarification the red thread (bobbin thread) marks the rights side of the fabric, and the purple (top thread) marks the back.
* This technique work well on chiffon, silks, peachskin, lining, or other lightweight fine fabrics.