What does pressing as you sew actually do?

People skip this because it means getting up from the machine constantly, and because a garment can be finished without it. But every seam that crosses an unpressed seam sits on a ridge, and those ridges accumulate. The difference shows most at collars, cuffs and waistbands, where several seams meet.

Safety

Step by step

1. Understand the difference from ironing.Ironing slides the iron across cloth to remove creases. Pressing lifts and lowers it in place. Sliding drags the fabric, and woven cloth stretches along the bias when dragged, which distorts a seam you have just sewn straight.
2. Set the seam first, before opening it.Press the seam closed, exactly as it came off the machine. This settles the stitches into the fabric and is the step most often missed. Then open it.
3. Open or press the seam to one side as the pattern requires.Open is usual for a plain seam in a woven; pressed to one side is usual for knits and for seams that need strength. Use a point presser or a rolled towel to reach into the seam.
4. Press each seam before another crosses it.Once a second seam crosses the first, the bulk is locked in and cannot be pressed out. This is the whole reason it is done as you go rather than at the end.
5. Test the heat on a scrap or a hidden seam allowance.Synthetics melt, and the mark is permanent. Some fabrics need a pressing cloth between the iron and the surface regardless of temperature.
6. Use a pressing cloth on anything dark or smooth.Direct heat and pressure flatten the raised yarns on the surface, which reflects light differently and reads as a shine. On dark wool and on twills it is very visible and difficult to reverse.
7. Let the piece cool before moving it.Fabric holds its new shape as it cools, not while it is hot. Lifting a warm seam off the board and folding it undoes the pressing you just did.
8. Use steam deliberately rather than constantly.Steam relaxes fibres and helps shape curves, and it also encourages some fabrics to shrink and some dyes to move. On an unfamiliar cloth, test it.

Tips

• A sleeve board or a rolled towel lets you press a seam open without pressing a crease into the layer underneath.
• Pressing from the wrong side avoids most shine problems and is the default for anything with a nap or a sheen.

Common mistakes

• Sliding the iron along a freshly sewn seam. — Woven fabric stretches on the bias when dragged, so the seam you sewn straight comes out wavy and cannot be corrected.
• Leaving all the pressing until the garment is finished. — By then every seam crosses another, and the bulk is sealed in where it cannot be reached.

Questions people ask