How to sew a seam that lasts, and a first pillowcase

Seam allowances by convention, a plain seam sewn and pressed, corners and curves clipped, the seam finishes and when each fits, and a finished pillowcase.

1. Seam allowances: a convention, not a standard Understand

A seam is a line of stitching that holds two fabric edges together. The seam allowance is the fabric between that stitching and the cut edge; the stitching line itself is the seamline. Purdue Extension's 4-H helper's guide defines seam allowance the same way and says it is usually 5/8 in but may be as little as 1/4 in (Purdue 4-H-929). After a seam is sewn, the allowances sit on the wrong side of the work, out of sight.

The allowance matters because every finished size in a pattern assumes it. If a pattern adds 5/8 in to each edge and you sew at 1/2 in, each seam adds 1/4 in to the finished piece: 1/8 in from each of the two edges it joins. Across the four side seams of a skirt that is 1 in of extra width. Oregon State's 4-H seams sheet says that keeping the allowance even, at the width the pattern gives, is what keeps a garment at its size and shape (Oregon State 4-H 320-19). Physical principle

How wide the allowance is depends on who wrote the pattern. Oregon State calls 5/8 in (1.5 cm) the standard seam allowance in a pattern, with narrower allowances in lingerie and some knit patterns. Extension projects for flat items often use 1/2 in: the University of Kentucky's junior 4-H guide sews its tote at 1/2 in and other bags in the same guide at 5/8 in, and Utah State's pillowcase uses 1/2 in. Quilting uses 1/4 in. Burda Style says most of its patterns include no seam allowance and recommends adding 5/8 in (1.5 cm) for seams and 1 1/2 in (4 cm) for hems, while noting that some of its models include them. Convention

So the rule a beginner can rely on is short: read the project's instructions for the allowance before you cut, and sew at that width. This manual uses 5/8 in for the practice seams, because that is what a commercial pattern will ask for later, and 1/2 in for the pillowcase, because that is what its source uses. Convention

Keeping the allowance even

You keep an allowance even by watching the cut edge against a guide, not by watching the needle. Oregon State's sheet describes three guides. Many machines have lines etched on the needle plate 1/8 in (3 mm) apart, labelled for common allowances. A magnetic or screw-on seam guide can be set at the width you need. Or a strip of tape on the machine bed, measured from the needle, does the same job; a cross line on the tape marks where to stop before a corner. Stitching and tension started this habit on paper (your first seam). Check your own needle plate against a seam gauge once; your manual says what its markings mean. Product-specific

2. Sewing and pressing a plain seam

A plain seam is two pieces placed right sides together and stitched along the seamline. Most other seams begin as one. Oregon State describes a good plain seam as smooth on the right side, without puckers or ripples, and without a ridge from the allowance showing through after pressing. That is the standard to check your own seams against, rather than perfect straightness.

The order of work

1. Place the pieces right sides together with the cut edges even and any notches matched (marking).
2. Pin at right angles to the edge, heads sticking out past the cut edge. Pull each pin just before the presser foot reaches it. Utah State says sewing over pins can break or dull the needle.
3. Set a straight stitch at the length your sample log says suits the fabric; 2.5 mm (10.2 SPI) is a common start on quilting cotton (stitch length). For a stretchy knit, Oregon State uses the narrowest zigzag or a stretch stitch instead.
4. Lower the needle into the fabric at the seamline, about 1/2 in from the top edge, sew forward two or three stitches, reverse back to the edge, then sew forward. Utah State backstitches three or four stitches at each end. The backstitch keeps the seam from pulling open at its ends (backstitching).
5. Guide, do not push or pull. Keep the cut edge on your guide line and let the feed dogs move the fabric.
6. Backstitch at the far end and cut the threads.

When the two edges are not alike, Oregon State's sheet says which goes on top. A curved or bias edge goes on top of a straight edge, so you can see it and keep it from stretching. An eased edge goes underneath, against the feed dogs, which help work in the extra length. A gathered or pleated edge goes on top, so you can control the fullness. Convention

Ease, in this construction sense, is the extra length worked into a seam when one edge is slightly longer than the one it joins; Purdue's glossary defines it that way. It is not the same as the fitting ease in Patterns and fit, which is room between a garment and a body (wearing ease).

Pressing a seam

Press each seam before another seam crosses it. Oregon State's seams sheet gives three steps. First, press the stitching flat as it was sewn, without opening it; this sets the stitches into the fabric. Second, open the allowances with the point of the iron. Third, press the open seam lightly. The sheet says to press it open first even when the allowances will end up on one side, because the final seamline comes out smoother. Pressing means lifting and lowering the iron, not sliding it, as Cutting, marking and pressing showed (pressing). Convention

Which way the allowances finally lie depends on the work:

• Pressed open: the usual choice for garment seams in Oregon State's sheet. Each allowance is finished separately.
• Pressed to one side: quilting and patchwork. Utah State's Baby Rail Blues presses toward the darkest strip, so the allowance does not shadow through a light fabric, and presses meeting seams in opposite directions so they nest flat. Seams finished together, such as an overcast pair or a French seam, also lie to one side.

Neither is more correct. The project's instructions say which; if they are silent, garments go open and patchwork goes to the darker side. Convention

Crossing a seam

Where one seam crosses another, Oregon State presses (and if possible finishes) the first seam before crossing it, pins the two seamlines together and pins the allowances flat so they do not fold under the foot, then trims the crossed ends to cut bulk.

3. Corners, curves and bulk

A straight allowance is the same length as its seamline. At a corner or curve it is not, and the fixes either let the allowance spread or take fabric out of it.

Corners

Oregon State's sheet shortens the stitch for about six to ten stitches before and after a corner, for control and strength where the seam turns. At a square corner, or any wider angle, stop with the needle down exactly at the corner, raise the foot, turn the fabric on the needle (pivot; Stitching and tension practiced it on paper, corners and curves), lower the foot and go on. At a corner sharper than a right angle, the same sheet takes one or two stitches straight across the point instead, which leaves room for the trimmed allowance when the corner is turned. Then return to the usual length. Convention

Before you turn a corner right side out, trim the allowance diagonally across the point, close to the stitching but not through it. Without the trim, the folded allowance fills the corner and it turns out round.

Curves

Oregon State's cutting sheet names two cuts. A clip is a straight snip into the allowance of an inward curve (one that curves in toward the piece, such as a neckline facing); it lets the allowance spread when the seam is turned. A notch, in this sense, is a small triangle cut out of the allowance of an outward curve (one that curves away, such as a round collar or pocket corner); it removes fabric that would otherwise bunch. Notch also means the matching mark on a pattern edge from Cutting, marking and pressing; context tells which. The sheet's figures:

• Clip or notch to within 1/16 in (1.5 mm) of the stitching, and not through it: a cut through the stitching opens the seam.
• Gentle curves need few cuts; sharp curves need more.
• Cut each layer separately and stagger the cuts, so they do not line up into a weak, sharp edge.

These are one extension service's figures; the curve itself tells you when there are enough cuts, because the turned seam lies flat without pulling. Convention

Staystitching is a line of regular-length stitching through a single layer, just inside the seamline, sewn right after cutting. Oregon State's cutting sheet uses it to keep curved edges from stretching while you handle them, and as the line you clip to.

Grading

Where two or more allowances lie together inside an enclosed seam (a facing, a cuff, a collar, the band of the pillowcase), their combined thickness can show as a ridge. To grade a seam is to trim each allowance layer to a different width, so the edges step down instead of ending in one thick line. Oregon State puts the widest layer toward the outside of the garment and the narrowest toward the body, and grades before clipping or notching. How narrow depends on the fabric's weight and how much it ravels. Utah State's pillowcase sheet grades the band seam in its trimmed version, for the same reason.

4. Seam finishes and when each fits

A woven fabric's cut edge ravels: threads work loose with wear and washing until, eventually, the seam has nothing left to hold. A seam finish treats the raw edge of the allowance so it does not ravel. Oregon State says knits and firmly woven fabrics may be left unfinished, lined garments may need none, and other fabrics need a finish. The sheet adds that a finish should not add bulk or show through to the right side, and suggests trying several on scraps of the real fabric. Ohio State's Franklin County handout says the same in its own terms: there is no single answer, and the requirement is a finish that is not bulky, is neat and stops raveling (Ohio State Extension, Franklin County, Seam Finishes). Test it

A self-enclosed seam is one that encloses its own allowances, so no separate finish is needed; Purdue's glossary uses the term and pairs it with sheer fabrics. The French and flat-felled seams are the two a beginner meets most.

The two finishes for your sample log

Zigzag. You can zigzag each allowance of an open seam, or press both allowances to one side and zigzag them together, as Franklin County does at armholes and waistlines; the sample here does the second. Set a zigzag with a short length and a medium width, and test it on a scrap first, as Oregon State says. On quilting cotton, a firm fabric, the right swing of the needle can land just off the edge so the stitch wraps it; on a soft fabric, stitch just inside the edge and trim to the stitching afterward. Check that the finished edge lies flat, does not ripple or stretch, and leaves no ridge when pressed. If it does, change the length, width or position and try again. Test it

Turned and stitched. Press the seam open. Fold the raw edge of one allowance under 1/8 in (3 mm), press, and stitch along the fold with a straight stitch. Repeat on the other allowance. It takes longer than zigzag and suits light to medium fabrics; on a thick fabric the fold adds bulk that can show through.

Log each sample on the settings sheet: fabric, needle, thread, stitch, length, width, tension and the result. The sample log you started in Stitching and tension is what Your project draws its settings from (the sample book).

5. The first piece: a pillowcase

A pillowcase uses only straight seams, one corner and one enclosed seam, and you can put it on a pillow the same day. This manual follows Utah State Extension's Designer Pillowcase for its sizes and order of work (Utah State, Designer Pillowcase). The sheet calls for firmly woven 100 percent cotton or a cotton and polyester blend at least 42 in wide, and two coordinating fabrics, one for the body and one for the border band (a folded strip that finishes the open end). One fabric for both works the same way. Preference

In centimeters, the standard pieces are 22.9 × 106.7 cm (band) and 68.6 × 106.7 cm (body). Your cut list already has the standard rows. The 42 in runs across the fabric, from selvage to selvage, and becomes the case's circumference; the 27 in runs along the grain and becomes its length. Cutting, marking and pressing cut and pressed these pieces (cutting).

The finished size follows from the seams. The 9 in band folds in half to 4 1/2 in, and the 1/2 in band seam takes 1/2 in of that: a 4 in band. The 27 in body loses 1/2 in at the band seam and 1/2 in at the bottom: 26 in. Together, 30 in. Across, 42 in folded in half is 21 in, less a 1/2 in side seam: 20 1/2 in. That is Utah State's case size, and it shows why the allowance matters: a French seam uses 5/8 in instead of 1/2 in, so under those figures the case comes out 1/8 in narrower and 1/8 in shorter, about 20 3/8 × 29 7/8 in. On a pillow, that difference is unlikely to matter. Physical principle

If the fabric measures less than 42 in after preshrinking and squaring (preshrinking), the case is narrower by half the shortfall. The selvages fall at the side seam. Utah State's skirt sheet removes selvages because they tend to shrink more than the rest of the fabric and can pucker a seam; trim them if your width allows it.

The band: a seam enclosed by rolling

Utah State joins the band with a method often called the roll method: the body is rolled up inside the band, the band seam is sewn through all the layers, and the body is pulled out through the end. The seam ends up inside the folded band, with no raw edge showing. In our own words, the order of work:

1. Lay the band right side up. Lay the body on it right side down, with one long edge of the body even with one long edge of the band. Pin those two edges, pins at right angles to the edge.
2. Roll the body up toward the pinned edge. Stop when the roll reaches the middle of the band.
3. Bring the band's free edge over the roll to meet the pinned edges, so the roll is wrapped inside the band like a tube. Re-pin through all three layers.
4. Sew the pinned edge with a 1/2 in seam, backstitching three or four stitches at each end. Keep the roll out of the seam; Utah State pins along the roll about 1 1/2 in in from the edge if it creeps.
5. Press along the stitching to set it.
6. Reach into the tube and pull the body out through one open end. The band is now folded, right side out, and the seam is hidden inside it.
7. Press the band and the seam flat from both sides until the wrinkles are gone.

Grading the band seam is optional on quilting cotton; it helps if your fabric is heavier and the band feels stiff along the seam (grading).

The side and bottom: two ways to close it

The case now needs one seam down the open side and across the bottom, with a pivot at the corner. Choose one of these two methods.

Utah State's way: a plain seam, finished.

1. Fold the case right sides together with the raw edges matched, the band seams lined up, and pin.
2. Sew a 1/2 in seam from the top of the band, backstitching to start, down the side to 1/2 in from the bottom. Stop with the needle down, lift the foot, pivot, lower the foot and sew across the bottom. Backstitch at the end.
3. Press the seam flat to set the stitches.
4. Finish the raw edges together with zigzag, the finish the sheet suggests (a three-step zigzag on lightweight fabric to avoid a puckered edge).
5. Trim the corner, turn the case right side out, push the corner out gently, and press.

Enclosed: a French seam. A French seam is sewn twice: first wrong sides together near the edge, then right sides together far enough from the fold to enclose the first allowance. Franklin County sews 1/4 in, then 3/8 in from the fold: 5/8 in in all. Its handout pairs the seam with lightweight and sheer fabric; we use it on the pillowcase because the seam is straight and leaves no raw edge inside. Preference

1. Fold the case wrong sides together (right side out), match the edges and band seams, and pin.
2. Sew 1/4 in from the edge down the side and across the bottom, pivoting 1/4 in from the corner, backstitching at both ends.
3. Press the seam, trim the corner diagonally close to the stitching, and trim any threads from the allowance so none poke through later.
4. Turn the case wrong side out. Push the corner out and press a sharp crease along the seam, so the first seam sits exactly on the fold.
5. Sew 3/8 in from the fold, pivoting 3/8 in from the corner. Backstitch at both ends. The first allowance is now enclosed.
6. Turn right side out and press, with the French seam lying to one side.

Test the corner on two scraps first if you have not sewn a French seam before. If threads from the first allowance show on the right side after the second seam, the first seam was too far from the edge or the second too close to the fold; trim the first allowance a little narrower before the second pass. Test it

6. See it: Dana's pillowcase See it

Free sources behind this chapter:

• Utah State Extension, Designer Pillowcase: the cut table for three pillow sizes and the roll method, with a trimmed variation.
• Oregon State 4-H, Plain Seams and Seam Finishes: seam guides, pressing in three steps, corners, and seven finishes with when to use each.
• Ohio State Extension, Franklin County, Seam Finishes: the French and flat-felled seams with their measurements and the garments each suits.
• Oregon State 4-H, Cutting Skills: grading, clipping and notching with drawings.

7. Practice: two seams, two finishes, one pillowcase Practice

Minimum: two practice seams with the two finishes logged, and the pillowcase sewn by either method. Time: about 2 hours; the pillowcase alone is about an hour once the pieces are cut. Materials: the pillowcase pieces from Cutting, marking and pressing, scraps of the same fabric, matching all-purpose thread, pins, a seam gauge, the iron and a pillow.

1. Check the machine. Thread it, put in the needle your sample log names, and sew a few stitches on a folded scrap to confirm the tension is still balanced (tension).
2. Find your 5/8 in guide. Measure from the needle with the seam gauge and confirm the etched line, or place tape.
3. Sew two 5/8 in seams on folded scraps about 6 in long, backstitching at each end. Press each in three steps; leave one open and press the other to one side.
4. Finish them. Turn and stitch each allowance of the open seam. Zigzag the two allowances of the side-pressed seam together, after a test on a single layer. Label each scrap with a pinned note: fabric, needle, stitch, length, width, tension.
5. Log both samples on the settings sheet, one row each, with the result and "sample kept".
6. Switch your guide to 1/2 in for the pillowcase.
7. Sew the band by the roll method, pull the body through, and press.
8. Close the side and bottom by the plain seam with zigzag or by the French seam. Press.
9. Trim threads, press, and put it on a pillow. Tick the pillowcase steps on the project steps sheet if you track them there.

8. Your sewing Your sewing

9. Check your work Check your work

Criteria

• Are both ends of every seam backstitched, with no stitches pulling loose?
• Does each seam sit at the allowance you meant (5/8 in for the samples, 1/2 in or the French seam's 1/4 and 3/8 in for the pillowcase), measured with a seam gauge at a few points?
• Is every raw edge inside the pillowcase either finished or enclosed?
• Is the bottom corner turned fully, without a hole or a lump?
• Are the seams pressed, with no pleats or puckers on the right side?
• Does the settings sheet have one row for each finish sample, with its settings and result?

Worked example

Dana's pillowcase (fictional) meets each criterion: backstitched at the band and at both ends of the French seam; the band seam measured at 1/2 in and the French seam's passes at 1/4 and 3/8 in; no raw edge inside, because the band seam sits inside the band and the French seam encloses the side and bottom; the corner turned square after trimming before the second pass; seams pressed. Her two finish samples are two rows on the settings sheet. The 3 in she resewed shows a slightly wavy line, which the criteria do not count against her. The fit on the pillow and the first wash are still to come.

Common mistakes

• Watching the needle instead of the edge against the guide, so the allowance wanders.
• Sewing the rolled body into the band seam. Pin along the roll and check the underside before you sew the last few inches.
• Starting a French seam with the right sides together. The first pass is wrong sides together; otherwise the allowance ends up outside.
• Skipping the press between the French seam's two passes, so the first seam is not on the fold and threads poke through.
• Clipping or trimming through the stitching at the corner, which leaves a hole.

What is still unresolved

This chapter cannot tell you how your seams and finishes wear. Washing the pillowcase and your samples as the fabric's care says will show it. The allowance for your next project is set by that project's instructions: the pillow cover, tote and garment in Your project each name their own, and a commercial pattern's envelope says whether allowances are included (pattern markings).

10. Knowledge check and scenario

Checklist

• I sewed two 5/8 in practice seams and pressed one open and one to the side.
• The settings sheet has a zigzag and a turned-and-stitched finish sample, each labelled.
• The pillowcase is finished, every raw edge finished or enclosed, and it is on a pillow.
• I sewed a flat-felled or Hong Kong sample, or the 1/4 in quilting seam test. (Go deeper; optional)
• I sewed a curve and corner sample with clips and notches. (Go deeper; optional)