An unlined jacket asks more of its seam allowances. Each inside seam remains visible and may rub against clothing, catch on jewellery, or receive the ordinary abrasion of wear. A Hong Kong seam finish encloses those raw edges in narrow bias strips while keeping the seam relatively light and supple.
Unlike a fully bound seam, where both edges of the binding are turned under, a Hong Kong finish leaves the underside of the bias strip raw. This is not a fault. The bias-cut edge frays very little, and the method reduces layers at the edge of a seam allowance. It is especially handsome in wool, linen, tweed, denim, and other woven fabrics used for unlined jackets and coats.
The work is slow enough to reward planning. Make and fit the jacket first; then bind the seams in a sensible order, pressing at every stage.
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When to choose a Hong Kong finish
Use this finish where the inside of the garment will be seen and where a serged edge would feel too casual or too stark. It gives a clean boundary to the seam allowance and allows a quiet contrast: cotton lawn against wool, striped shirting inside a plain jacket, or a close tonal batiste that appears only when the jacket opens.
It is particularly useful for moderately straight seams and for fabrics whose seam allowances would become thick if flat-felled. On a substantial coating or loosely woven cloth, the separate bound allowances can be easier to manage than a conventional pressed-open raw edge.
There are limits. A sharply curved seam that must be deeply clipped or notched is difficult to bind cleanly. Very bulky fabrics may need wide, carefully graded seam allowances, and some areas are better left for another treatment. Consider a narrower binding, a simple overcast edge, or a lining for tight armholes, heavily shaped princess seams, and places where several seams meet.
A Hong Kong finish is also best treated as an interior finish. Do not use it in place of a facing, hem finish, or neckline binding unless the garment pattern specifically calls for it.
Materials and preparation
Choose a lightweight, stable woven fabric for the binding. Cotton lawn, batiste, fine shirting, lightweight silk, and similar fabrics work well. The binding should be lighter than the jacket fabric; a thick or stiff strip adds bulk and can make a seam allowance buckle.
You will need:
- The partly constructed jacket or coat
- Lightweight woven fabric for bias strips
- Matching thread
- Sewing machine with a fresh, suitable needle
- Iron and pressing cloth if needed
- Pressing ham or seam roll
- Sharp shears or rotary cutter, ruler, and cutting mat
- Seam ripper for correcting small misses at the ditch
Before cutting binding, decide on the finished width. A finished edge of about 6 mm to 1 cm is usually suitable for jackets. Cut strips roughly four times as wide as the intended finished width. For a 6 mm finish, begin with strips about 2.5 cm wide. Slightly wider strips are easier to handle, particularly on a first jacket, and can be trimmed after stitching.
Cut and join the bias strips
True bias runs at a 45-degree angle to both the lengthwise and crosswise grain. Fold a square corner of the binding fabric diagonally so that a selvage meets a cross-grain edge; the fold marks the bias direction. Cut strips along this line.
Bias strips must be long enough to cover each seam allowance with a little extra at both ends. To join shorter strips, place two ends right sides together at a right angle, forming an L shape. Sew diagonally from corner to corner. Trim the seam allowance to about 6 mm, press it open, and trim away the small triangles that extend beyond the strip. The joined strip should lie straight and smooth rather than forming a thick step.
Do not pull the strips while cutting, joining, or sewing. Bias stretches easily; stretched binding will ripple after it is applied.
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Sew the jacket seams first
Construct the garment according to its pattern instructions, but pause before any step that would conceal or make a seam inaccessible. In many jackets, it is easiest to bind shoulder seams, side seams, panel seams, and sleeve seams before setting the sleeves into the body. The best order depends on the pattern and the number of intersections at each seam.
Press each completed garment seam open before binding. A well-pressed seam is the foundation of a neat finish. If the fabric is thick, grade the seam allowances where appropriate: trim one allowance slightly narrower than the other so that the layers do not create a ridge. Take care not to reduce seam allowances in areas that may need alteration.
Bind each seam allowance separately. This allows the seam to remain pressed open and avoids the heavy, rope-like result of wrapping both allowances together.
The basic Hong Kong seam method
1. Align the binding
Lay the jacket wrong side up with one seam allowance spread flat. Place a bias strip right sides together with the raw edge of that seam allowance. Align their raw edges. Let the binding extend beyond the seam at each end by at least 2.5 cm.
The rest of the garment should be folded away from the needle. You are stitching only through one seam allowance and one bias strip, not through the body of the jacket.
2. Stitch close to the raw edge
Sew along the aligned edge using a seam allowance of about 6 mm. Keep the strip smooth without stretching it. On a gentle curve, guide the jacket seam allowance steadily and allow the bias to follow the curve; do not force either layer flat.
Backstitch lightly at the beginning and end, or leave thread tails if you prefer to secure them by hand in a delicate fabric.
3. Press the binding away from the seam allowance
Open the binding and press it away from the seam allowance, with the stitching line pressed flat. A seam roll or ham supports curved areas and prevents a hard imprint from showing through on the garment’s right side.
At this point, check the raw edge. If the jacket fabric frays excessively or the seam allowance is uneven, trim it carefully before wrapping the binding around it. Do not trim so close that the first line of stitching is weakened.
4. Wrap the binding to the underside
Turn the free edge of the bias strip around the raw edge of the seam allowance and bring it to the underside. The binding should cover the first stitching line by a small amount.
From the right side of the seam allowance, stitch in the ditch: sew directly in the groove where the binding joins the seam allowance. The underside of the binding should be caught in this stitching. Go slowly, especially at joins in the bias strip and near seam intersections.
There should be little or no visible second line of stitching from the jacket’s interior-facing side. On the reverse of the seam allowance, the binding will show a neat line of stitching close to its folded edge.
5. Trim and press
Trim the excess binding close to the underside stitching, leaving a narrow raw bias edge. This is the characteristic finish. Do not cut into the stitching.
Press the completed bound allowance flat, then press the seam open again from the garment’s wrong side. Use only the heat and steam appropriate to the jacket fabric. A pressing cloth is sensible for wool, silk, dark cloth, or any fabric that may shine.
Repeat the process on the second seam allowance.
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Handling ends, corners, and intersections
A bound seam is easiest when its ends disappear into another construction seam, a facing, or a hem. In these places, leave a small extension of binding beyond the seam allowance; it can be enclosed later when the next piece is attached.
Where a seam ends in an exposed place, such as near an open vent, fold the binding extension to the underside before the final ditch stitching. This gives the end a closed, tidy appearance. Reduce bulk by trimming the extension before folding it, rather than stacking several full-width layers.
At a seam intersection, decide which seam will be bound first. Usually, bind the less accessible seam before sewing the crossing seam. Keep the last few centimetres near an intersection unbound until you can see how the layers will lie. This small pause prevents a dense knot of binding inside the garment.
For gently curved seams, use a narrower strip and stitch slowly. If the curve requires many deep clips or notches, a Hong Kong finish may not sit well. A narrower seam allowance finished with a zigzag, overcast stitch, or a very lightweight bias binding applied with extra care may be more practical.
Common mistakes to avoid
Binding before fitting
A Hong Kong finish makes alterations more time-consuming. Complete fitting adjustments before you bind long structural seams, especially centre-back, side, and sleeve seams.
Using fabric that is too heavy
A binding fabric that resembles the jacket cloth in weight may look impressive at first but can make the seams rigid. Reserve heavier binding for very open-weave or exceptionally substantial fabrics, and test the combination on a seam sample.
Stretching the bias strip
Pulling the strip as it passes beneath the presser foot creates a wavy edge. Support the strip in front of and behind the needle, letting the feed dogs move it through naturally.
Missing the underside in the ditch
This happens often and is easily repaired. Turn the work over after a short section of stitching. If the binding has not been caught, unpick only that section, smooth the binding farther over the first stitching line, and sew again.
Binding every seam automatically
The finish is most effective where it can be seen and where bulk is manageable. Some hidden seams may be better left plain until they are enclosed by a facing, while tightly curved areas may benefit from a simpler finish.
Final pressing and care
Once all accessible seam allowances are bound, give the jacket a final careful press. Press rather than iron: lift and lower the iron instead of pushing it back and forth, particularly over bias binding and textured cloth. Use a ham for curved seams and a clapper, if appropriate for the fabric, to set crisp pressed edges without flattening the garment’s shape.
A Hong Kong seam finish will not make a jacket indestructible, but it protects vulnerable cut edges and gives the inside the same deliberate character as the outside. The small amount of extra time is most visible at the moments when the jacket is hung up, opened, mended, or handed from one pair of hands to another.