Sewing with silk: cutting, needles and seams

Silk sews well once you stop it moving: cut it in a single layer on paper with weights and a rotary cutter, sew with a new 60/8 or 70/10 microtex needle, fine polyester or silk thread and a 2 mm stitch, and enclose the raw edges in French seams. Start with a crepe de chine or a dupioni rather than a charmeuse, and pre-wash only if you intend to wash the finished garment.

Which silk should you sew first?

Silk is a fiber, and it is woven into fabrics that range from crisp to liquid. The weave matters far more than the word "silk" when you choose a project.

Chiffon has its own rules; see sewing with chiffon. Everything below applies to the opaque silks.

Quick reference: how to sew silk

Should you pre-wash silk?

Only if you plan to wash the garment, and then yes, because washed silk changes. Hand wash the length in cool water with a mild detergent or a little shampoo, never wring, roll it in a towel and press it from the wrong side while still damp. Crepe de chine shrinks and gains a little texture; charmeuse comes out softer with slightly less sheen; habotai barely changes. Test a 20 cm (8 in) square first and measure it before and after.

Dupioni and shantung lose their crispness and can water-spot, so keep them dry-clean only and skip the pre-wash. Whatever you decide, treat the finished garment the same way you treated the fabric.

How do you cut silk without it shifting?

1. Cover the table with a cotton sheet or a layer of pattern paper. Silk slides on a smooth surface and clings to cotton.
2. Lay the silk in a single layer, right side up, and smooth it from the center outward without stretching. Check the grain by pulling a crosswise thread near the cut end if the edge looks skewed.
3. Hold the pattern with weights, not pins, and cut with a sharp rotary cutter in one continuous stroke per edge. Shears lift the fabric; if you must use them, keep the lower blade on the table.
4. Flip the pattern to cut mirrored pairs. Cutting in a single layer means every sleeve and front is cut twice.
5. Mark on the wrong side with tailor's tacks or a chalk pencil inside the seam allowances, and cut notches outward. Fine silk pins, if you need them, go inside the allowances only.

Spray starch stiffens silk enough to make this easier and washes out afterward; test it on a scrap. For a bias-cut slip, lay the pieces at 45° to the selvage in the same single layer.

Which needle, thread and stitch length work for silk?

A microtex needle has a slim, very sharp point that pierces the fine yarns instead of pushing them aside, which is what causes pulled threads and runs. Fit a new one: run a fingernail down the old one and you will often feel the burr that was snagging. Match the size to the weight: 60/8 for the lightest, 70/10 for most dress silks, 80/12 for dupioni.

Fine thread makes a fine seam. A 60 weight polyester or a silk thread sinks into the fabric; regular 40 weight all-purpose thread sits on top and puckers light silks. Set a stitch of 1.8–2.2 mm, lower the upper tension by a notch if the seam draws up, and reduce the presser foot pressure if your machine allows it. Then test on a scrap folded double.

How do you sew silk seams without puckering?

Light silk puckers when the needle pushes it down into the hole of the needle plate. A straight-stitch plate, with a single small hole, removes the problem; failing that, a strip of tissue paper under the seam does the same job and tears away afterward. Hold the thread tails as you start, or start on a small scrap and chain into the seam so the first stitches have something to grip. Sew with the fabric held lightly taut in front and behind the foot, without pulling it through. Do not backstitch; tie the ends.

Staystitch necklines and other curves within the seam allowance as soon as they are cut. Then enclose every seam. A French seam in a 1.5 cm (5/8 in) allowance, the default Sewly draws on woven fabrics, goes like this: sew wrong sides together 0.9 cm (3/8 in) from the edge, trim the allowance to 3 mm (1/8 in), press the seam to one side and then fold right sides together along the stitching, press, and sew 6 mm (1/4 in) from the fold. The raw edges are inside and the seam looks the same on both faces.

How do you press silk?

Use the silk setting, around 150 °C (300 °F), a press cloth of silk organza or cotton lawn so you can see through it, and a dry iron or the least steam that works, because some silks water-spot. Press from the wrong side, and slip strips of paper under seam allowances so their edges do not print through to the right side. Press each seam before another seam crosses it, and let the piece cool flat before moving it. Test the temperature on a scrap: too hot and silk turns dull and brittle.

How do you hem silk?

A narrow hem suits almost every silk. Stitch 1 cm (3/8 in) from the raw edge, fold along the stitching and press, stitch 2 mm (1/16 in) from the fold, trim the excess close to that line, fold once more to enclose it and stitch again. A rolled hem foot does the same in one pass once you have practiced on scraps. On charmeuse or a scarf, a hand-rolled hem is the classic finish. The variations are in how to sew a rolled hem. Bias-cut pieces need to hang for a day before the hem is marked and sewn.

What should you sew with silk?

• A slip dress in charmeuse, cut on the bias. It is the hardest of these three, so make it your second or third silk. The slip dress pattern has only a few seams, which keeps the handling manageable.
• A woven top in crepe de chine: a shell with bias-bound neckline and armholes, or a button-front blouse. The woven top pattern is the project most people should sew first in silk.
• Scrunchies in charmeuse scraps: the scrunchie pattern is a 10 minute way to test needle, thread and stitch length before the real project.