French Seam
French seam is a sewing method in which the raw edge of the seam allowance is enclosed by stitching twice, resulting in a clean finish on both the front and back while preventing fraying.
Contents6 sections
Definition and Overview
A French seam is a finishing method in which the seam allowance is first loosely joined with the first seam, then stitched a second time to enclose the seam allowance. When finished, the raw edge is contained inside the seam allowance, so edge finishing with an overlock machine or similar is not visible from either the front or back.
It is mainly used for woven fabrics from lightweight to medium-lightweight, and is suitable for products that need to prevent fraying while keeping the inside, which touches the skin, looking neat. Because the seam allowance is layered at the seam, it may not be suitable for thick or stiff fabrics, or for sharp curves.
Position in Product Making
A French seam is a process that combines seaming after cutting and edge finishing to handle the raw edge in one step. It is used on comparatively straight joining sections such as side seams, underarm seams, and body panels for shirts and blouses.
Specifying a French seam in the specification can improve appearance and comfort against the skin, but it changes the process order and seam allowance settings compared with separating normal seaming and edge finishing. In the planning stage, confirm the pattern, sewing specification sheet, factory equipment, and workability together.
Basic Procedure
In general, first place the fabric face side out and sew the first seam, then trim the seam allowance narrow. Next, turn it face side in and press it into shape with an iron, then sew the second seam at a position that can enclose the first seam allowance. In this way, the raw edge is sealed inside.
The position of the first and second seams and the final seam allowance width are set according to fabric thickness, tendency to fray, design, and required strength. If the first seam allowance is too wide, the second seam may not fully enclose it; if it is too narrow, the seam may slip out or lack strength.
- When cutting, secure the seam allowance required for a French seam in the pattern.
- After sewing the first seam, even out the seam allowance width and trim any excess.
- After turning, open the seam allowances fully or press them to one side before sewing the second seam.
- For lightweight or slippery fabrics, check for seam shifting, puckering, and waviness in the stitches.
Ordering and Quality Points
When placing an order with a sewing factory, clearly indicate in the specification sheet and drawings the sections to be finished with a French seam, the front/back designation, the finished seam allowance width, and the stitch position. If it is used only in certain areas, such as side seams only, also specify the transition points from areas finished with normal edge finishing.
In quality inspection, check whether the raw edge of the seam allowance is not protruding from the second seam, whether the seam widths are even, and whether there is no puckering or seam shift on the front side. Because the seam allowances overlap, check for sheerness in light-colored, lightweight fabrics and for step marks or fading in dark-colored fabrics.
Assuming loads from washing and wear, also confirm seam opening, broken thread, and protruding fabric edges in prototypes. For fabrics with a loose weave, fabrics that tear easily, or knit fabrics with high stretch, finishing methods other than a French seam may be more suitable.
Difference from Similar Terms
A flat-felled seam also encloses the seam allowance and hides the raw edge, but it is generally a construction in which one seam allowance covers the other, with an additional stitch visible on either the front or back. A French seam encloses the raw edge inside with the second seam, giving the visible side a relatively neat appearance.
An overlock is an edge finishing method that suppresses fraying of the raw edge with an overcasting stitch. Its process and finish differ from a French seam, and in a French seam the fabric edge itself is enclosed within the seam allowance. In addition, bag weaving is a term for a woven structure, and is different from the sewing specification term French seam.
Frequently Asked Questions
What kinds of fabrics are suitable for a French seam?
In general, it is suitable for woven fabrics from lightweight to medium-lightweight such as lawn, voile, and chiffon. Because the fabric edge can be enclosed inside, it is used for fabrics that fray easily and products that need a neat inside finish. On the other hand, thick fabrics, stiff fabrics, textured fabrics, and sharply curved areas tend to become bulky at the seam allowance, so check with a sample first.
How should a French seam and a flat-felled seam be used differently?
A French seam encloses the raw edge inside the seam allowance with two rows of stitching, so it is suitable when you want a clean inside finish on lightweight shirts and blouses. A flat-felled seam presses the seam allowance to one side and secures it with stitching, so it is chosen when seam strength or a design that shows the stitching is emphasized.
What should be noted when writing a French seam into the specification sheet?
Illustrate the sections to be finished with a French seam, the final seam allowance width, the direction the seam allowance is turned, and whether visible stitching appears on the front side. It is also important to confirm whether the seam allowance amount on the pattern suits the process. Because seam thickness, sheerness, and seam shift vary by fabric, agree on the finishing standard with a sample or pre-production sample before mass production.
