Stay-stitching is the stitching done along the cut edge of fabric pattern pieces ready to be stitched into a garment. It is done to prevent the edges from stretching out of shape – you get smooth, even stitching without stretched fabric.
This is usually done along curved edges and those edges that are cut across the grain (bias cut) like that of necklines, armholes, shoulder seam and for fabrics that tend to stretch like all knits, and along diagonally cut fabric pieces. It is done 1/8 inch from the cut edge and made before the seams are stitched.
Stay stitching is done just after you have cut the pattern pieces. This will prevent the edges from stretching more than is necessary. Stay stitching is done to keep the fabric pattern pieces the same dimension as before even after all the pulling and pushing the fabric pieces will undergo while sewing and pressing. It is a good dressmaking technique, which can be avoided but at the risk of beauty and integrity of the garment.
How to stay stitch
Stay stitch is a simple straight stitch line, done with a matching thread as that of the fabric. The direction of doing it is as in the picture above. Usually it should be in the direction of the grainline of the fabric.
Use a measure slightly less than the measure of the seam allowance you intend to use or given in your commercial pattern. You simply stitch along the cut edge, about 1/8 inch to 1/4 inch inside from the cut edge, depending on the seam allowance used. For a 5/8 inch seam allowance, you can sew 3/8 inch from the raw edge.
Care should be taken that the stitching is not done inside the marking done for the seam line – or else it will be visible to the outside after you sew the seam. ie the stay stitching is done between the cut edge and the seam line. You may want to use a tool like a seam gauge to be exact.
The stay stitching is especially important for necklines – if the neckline edge stretches, the finished neckline can gape or sag. It is also done along the shoulder seam, cutting done for inserting plackets, and zippers, and the lower edge of the bodice (waistline). Anywhere that you feel there will be distortion, due to fabric stretching.
For necklines, you should be stitching down from the upper edge on both sides to the middle. For shoulder edges, you can sew the stay stitch from the neckline edge to the outside. For other bias edges, stay stitch from the top to down. For the waistline edge, you can stay stitch after the darts are stitched.
The stay stitching remains on the fabric reinforcing the edge forever- no need to remove the stitching at all. You can clip on the curve edge beyond the stay stitching.
A Stay tape is a thin tape used to reinforce a cut edge and to prevent stretching, similar to how stay stitching would do. It is added to the back of the cut edge or under the seam.
Related posts: Step by step sewing for beginners; Names of tapes for sewing.