Why do seams pucker on chiffon, silk and lawn?

Puckering that starts at the machine

Sheer and slippery cloth shows every small fault in the sewing. Lawn is more forgiving because it is a stable, close cotton weave, but very fine lawn and voile can still draw up. These are the common causes:

• Tight tension. When the threads are pulled hard, they squeeze the weave together along the seam. On chiffon the ripple shows the moment the seam is finished.
• Very short stitches. Many needle holes close together crowd a fine weave and shorten it. A slightly longer stitch often lies flatter on sheers.
• A blunt or thick needle. Instead of passing cleanly between the threads it pushes them aside or snags them, which drags the line on silk in particular.
• Layers creeping. The machine feeds the lower layer a little faster than the upper one, so slippery fabrics shift and one side ends up gathered.
• Off-grain seams. Edges cut slightly on the bias stretch as they pass under the needle, then relax into waves once sewn.

Puckering that appears after washing

If the seams were flat when the outfit arrived and rippled after its first wash, the parts have shrunk by different amounts. Cotton lawn can tighten a little on its first wash while polyester thread barely moves, so the fabric shortens around a line that stays the same length. The reverse happens when cotton thread is used on a polyester chiffon. Pre-washing washable fabric before it is cut, as our guide on whether to pre-wash fabric explains, removes much of that risk.

Corded piping is the classic case. The cord inside is often cotton and can shrink more than the fabric wrapped round it, which turns a crisp piped neckline wavy. Pre-shrunk cord, or flat piping with no cord at all, avoids it. The piping and trims guide shows where piping usually sits. Fusible interfacing can do something similar if it shrinks or lifts away from the fabric, which shows as small bubbles around a collar or placket.

What pressing can and cannot put right

Pressing helps more than people expect, but only with mild cases. A gentle steam, with a pressing cloth on silk and a low heat on synthetics, can settle stitches into the cloth and relax a faint ripple. A cotton seam that has drawn up slightly after washing can sometimes be eased by steaming it and stretching it lightly along its length while it is still damp. Our page on ironing and steaming kurtas covers heat settings for each fabric.

Pressing cannot lengthen a thread that is too short or put shifted layers back in line. A cord that has shrunk stays shrunk. A seam that is plainly gathered only goes flat if it is unpicked and sewn again, and on chiffon the old needle holes may still show.

What to mention before a fine fabric is stitched

Most puckering is prevented before the first cut, so it helps to give whoever stitches your outfit the facts about the cloth and how you will look after it. For Stitching Only, put these in the notes when you send your fabric details through our Stitching Only service, then ask for a quote. The seam and edge finishes are confirmed in the written quote, not assumed.

• The fabric name, or a clear photo if there is no label (see describing unlabelled fabric).
• Whether the fabric is pure silk, a silk blend or polyester, since thread is chosen to suit it.
• Whether you have already washed it.
• Whether you want piping, and if so flat or corded.
• How you plan to wash the finished outfit: by hand, by machine or dry cleaning only.