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Teaching Tools - Seam Basics


The best way to see if you want to sew is to start small and just make small samples of the various seams and seam finishes on a piece of muslin that you can fit into a scrapbook. This scrapbook can then be used as a handy reference tool. As you improve your skills you can add to your book. In this lesson we will start with stitching basic seams. In a later lesson we will move on to a small patternless project.

Seams and Seam Finishes


Seams are the backbone of your sewing. Happily, there’s nothing to learn about seams that’s difficult to grasp. Once you know the techniques, you’re on your way to wonderful sewing results.

A seam is basically a line of stitching that joins two or more layers of fabric. Seams are stitched on the seamline. The seam allowance is the distance between the seamline and the cut edge. Unless your pattern instructions tell you otherwise, the standard seam allowance is 5/8" (l.5cm) wide.

Seam Techniques


Some seams require special handling. Here are some terms and techniques you should be familiar with:

I. TYPES OF Seams


Although the plain seam is the one that you’ll use most often, there are other choices. You might want a specific decorative look or you might be using a fabric that requires some special handling. The plain seam usually requires a seam finish. However, many of the other seams highlighted here incorporate the seam finish into the seam technique. Remember: Your pattern instructions will probably use a plain seam but you have the option of changing that, depending on your fabric. Be sure to make a sample seam in some scraps of your fabric before you begin your project.

Before starting your scrapbook here are a few items you will need before you begin:

l Scrapbook, 1 yd (0.90m) of muslin, ruler, pencil or marking pen, thread (contrasting to see your stitches more clearly)

Using your ruler and pencil, mark and cut two 8” squares of your muslin fabric for each scrapbook sample you will be making. Mark a 5/8” (1.5cm) seam allowance on the wrong side of each piece. Then pin the two pieces with right sides together and the marked seam line face up. Pin the edges together and make the following samples for your reference book.

Plain Seam


The plain seam is the one you will use most often; it is suitable for any type of fabric, whether it’s woven or knit, soft or crisp, lightweight or heavier weight.

With right sides together, stitch along the seamline, which is usually 5/8" (1.5cm) from the cut edge, with a regulation-length stitch.

ress the seam flat to set the stitches.

Open the fabric and the seam allowance, so that the right sides of your fabric are no longer together; press the seam open.

Double-Stitched Seam


This is a combination seam-and-edge finish that creates a narrow seam especially good for sheers (such as chiffon and organza) and knits. To prevent the fabric from raveling, it’s stitched twice.

Stitch a plain seam.

Stitch again, 1/8" (3mm) away, within the seam allowance, using a straight or zigzag stitch.

Trim close to the second row of stitching.

Press the seam flat to set the stitches.

Open fabric so that right sides are no longer together; press the finished seam allowance to one side.

Stretch Knit Seams


Stretch knits need seams that are supple enough to “give” with the fabric. You can sew them with straight stitches, zigzag stitches or one of the stretch stitches built in to many conventional machines, or on your serger.

There are several variations utilizing the straight stitch and the zigzag stitch. Make samples of these seams on squares of knit fabric, such as cotton interlock or jersey. To prepare the fabric for samples, follow the same steps as for your muslin samples. Try the following seam techniques:

Stitch a plain seam with a straight regulation stitch, stretching the fabric slightly as you sew. Stretching the fabric keeps the stitches slightly looser, so that they don’t “pop” as the seam wears.

For extra strength, stitch a double-stitched seam, also with a straight regulation stitch.

Another option is to stitch along the seamline with a straight or a narrow, medium-length zigzag stitch. Then zigzag 1/4" (6mm) away, within the seam allowance, and trim close to the last stitching.

If your machine has a built-in stretch stitch, consult your owner’s manual for instructions. Usually, the seam allowance must be trimmed before stitching.

Stabilizing Knit Seams


Seams at the neckline, shoulders and waistlines should not stretch. If they do, the knit garment will lose its shape. Stabilize these seams by stitching seam binding or twill tape into the seams…or use Stay-Tape™, a lightweight stabilized nylon tape that works well on lightweight knits and curved edges.

Flat-Fell Seam


The flat-fell seam is frequently used on sportswear, menswear and reversible garments.

With the wrong sides of the fabric together, stitch a plain seam. Open the fabric so that the wrong sides are no longer together. Press the seam allowances to one side, so that one seam allowance lays on top of the other.

a) Trim the underneath seam allowance to 1/8" (3mm).

b) Turn under 1/4"(6mm) of the top seam allowance and baste it in place over the trimmed edge. (For quick sewing, use pins or glue stick instead of hand basting.)

c) Edgestitch close to the fold.

French Seam


This seam adds a couture look to the inside of garments made from sheers and lightweight silks. The finished seam, which should be very narrow, completely encloses the raw edges of the seam allowances.

a) With the wrong sides together, stitch a 3/8" (1cm) plain seam.

Trim the seam allowances to a scant 1/8" (3mm).

Open the fabric and the seam allowance, so that the right sides of your fabric are no longer together; press the seam and seam allowances open.

b) Fold the fabric right sides together along the stitching line; then press. The 1/8” (3mm) trimmed seam allowance should be now encased inside this fold.

c) Stitch 1/4" (6mm) from the fold. Open fabric so that right sides are no longer together; press the finished seam allowance to one side.

Lapped Seam


This type of seam is frequently used on nonwoven fabrics, suchas synthetic suede and leather, as well as real suede and leather, because their edges do not fray.

Trim away the seam allowance on one of your squares. This will be the “upper” section of the seam.

Lap the upper section over the second fabric square, placing the trimmed edge along the lower square’s seamline; hold it in place with hand basting, double-faced basting tape, glue stick or fuse basting.

Edgestitch along the trimmed edge, going through both upper and lower layers. Topstitch on the overlap 1/4" (6mm) away from the first stitching line, again going through both layers of fabric.

Topstitched Seam


This treatment accents the seamlines. It also helps keep the seam allowances flat—a great benefit when you’re working with crease-resistant fabrics. You can use a straight, zigzag or decorative stitch for the topstitching, whichever you prefer.

With right sides together, stitch a plain seam with a regulation straight stitch. Open fabric so that right sides of fabric are no longer together; press fabric and seam allowances open.

Working on the outside of the sample (right side of fabric up), topstitch on both sides of the seam 1/8" to 1/4"(3mm to 6mm) from the seamline, stitching through both fabric and seam allowances.

As an alternative:


With right sides together, stitch a plain seam with a regulation straight stitch. Open fabric so that right sides of fabric are no longer together; press seam allowances to one side.

Working on the outside of the sample (right side of fabric up), topstitch on one sides of the seam 1/8" to 1/4"(3mm to 6mm) from the seamline, stitching through all layers (1 layer of fabric, both layers of seam allowances).

Welt Seam


This type of seam is a good way to reduce bulk and hold seam allowances flat on heavyweight fabrics. From the outside, it looks like a topstitched seam; the double-welt version looks like a flat-fell seam.

With right sides together stitch a plain seam with a regulation straight stitch. Open fabric so that right sides of fabric are no longer together; press seam allowances to one side so one seam allowance lays on top of the other.

Trim the underneath seam allowance to a scant 1/4" (6mm).

On the outside (right side up), topstitch 1/4" (6mm) from the seam, catching the untrimmed seam allowance underneath. You will be stitching through 2 layers: 1 layer of fabric, and 1 layer of seam allowance.

For a double-welt seam, make a regular welt seam; edgestitch close to the seam line. Like the topstitching, this edgestitch will go through 2 layers of fabric.

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