French seams are used on thin, more delicate fabrics like various silks and chiffon that are easily damaged by zig zag or serging finishes. French seams wont pull and damage the threads of fine weaving and allow for a more durable, smooth finish. This is a higher quality, more expensive sewing technique that requires you to encase the raw edges of the fabric with two separate stitches, which in terms creates a clean look on both the face and wrong sides of the garment. Follow the steps bellow to learn how to sew a french seam at 1/2" seam allowance.
Step 1: Align and Pin the Seam
Pin the seam together with the right side of the fabric facing the outside. Pin perpendicular to the edge so that it's easier to remove the pins as you stitch on your sewing machine.
Note: In this tutorial, the lighter color is the face of the fabric.
Step 2: Apply a Machine Stitch at Half the Seam Allowance
Stitch on your sewing machine at half the seam allowance from the seam's edge. Since our seam allowance is 1/2", this initial stitch will be applied at 1/4".
Step 3: Iron Excess Seam Allowance
Iron the excess seam allowance (1/4") towards one side of the seam as shown.
Step 4: Fold the Seam to Enclose Raw Edge
Fold the seam so that the raw edge of the excess seam allowance is enclosed between the two layers of fabric. Keep in mind that the wrong side of the fabric should be facing the outside.
Note: The wrong side of the fabric in this tutorial is darker.
Step 5: Pin the Fold to Keep It in Place
Pin the fold horizontally as shown, thus keeping it stable for final stitching.
Step 6: Sew at Half the Total Seam Allowance
Stitch on your sewing machine at half the total seam allowance from the fold's edge. Our total seam allowance is 1/2", so this stitch will be applied at 1/4" away from the edge.