To press seams properly, press every seam twice before you cross it with another: first flat, exactly as it was sewn, to sink the stitches into the fabric, then open or to one side, with the iron lowered onto the seam and lifted off rather than pushed along it. Use the heat the fiber can take, a pressing cloth on anything that might shine, and a tailor's ham under every curve. The difference between a garment that looks homemade and one that looks made is almost always this step, not the stitching.
What is the difference between pressing and ironing?
Ironing slides the iron across a finished garment to remove creases. Pressing is lifting the iron and lowering it onto one place, holding it for a few seconds, lifting it and moving on. Sliding stretches fabric, especially on the bias and on curves, and drags the seam out of shape while the fibers are hot and pliable. Pressing shapes the fabric and lets it cool in that shape.
Steam helps on wool, cotton and linen; it relaxes the fibers so they take the new position. Let the seam cool before you move it. A hot seam picked straight up from the board loses half of what you did.
What do you need to press seams?
- An iron with a reliable temperature dial and steam. It does not need to be expensive; it needs a clean, flat soleplate.
- A pressing cloth: a square of silk organza (you can see through it) or plain cotton muslin, about 40 cm (16 in) square.
- A tailor's ham for curves, and a seam roll or a rolled towel for long straight seams.
- A point presser or a wooden clapper if you sew tailored pieces; a thick wooden ruler stands in for the clapper.
- A spray bottle of water for fabrics that take damp pressing.
What temperature should you press at?
Set the iron for the most delicate fiber in the fabric. A polyester-cotton blend is pressed at the polyester setting, not the cotton one.
| Fiber | Setting | Steam | Pressing cloth |
|---|---|---|---|
| Linen, cotton | Hot (3 dots) | Yes | On dark colors to avoid shine |
| Wool | Medium-hot (2 to 3 dots) | Yes, never let the soleplate touch | Always |
| Silk | Medium (2 dots) | Dry or light steam, test for water spots | Always |
| Viscose, Tencel | Medium (2 dots) | Light | On the right side |
| Polyester, nylon | Low (1 dot) | Little or none | Yes, it glazes easily |
| Acetate, acrylic | Low, test first | None | Always |
When you are unsure, press a scrap with a seam in it. Shine, a glazed surface or a changed hand means the iron is too hot or the cloth is missing.
How do you press a seam step by step?
- Press the seam flat, as sewn, with both allowances together, the way they came off the machine. This melds the stitches into the fabric and evens out the thread tension. Five seconds along each section.
- Open the seam with your fingers on the board, wrong side up, running a fingernail along the stitching line.
- Press the seam open from the wrong side, the tip of the iron running down the center, lowered and lifted section by section. On a straight seam, lay it over a seam roll so the allowances fall away and their edges do not print through to the right side.
- Let it cool, then check the right side through the pressing cloth, with a light press to settle the surface.
- For a seam pressed to one side (knit seams, serged seams, yoke seams, the seams of a lining), press flat as sewn first, then fold both allowances the way the instructions say and press from the wrong side, then from the right side through the cloth. Press toward the darker or the heavier piece unless told otherwise, and toward the back on side seams and shoulder seams.
- For a curved seam such as a princess seam, a neckline facing or a sleeve cap, slide the tailor's ham under the seam so the curve of the ham matches the curve of the garment, and press in short overlapping presses. Pressing a curve flat on the board sets it flat, and it will never sit against the body properly again.
- Press darts over the ham, from the wide end toward the point, with the fold of the dart toward the center on vertical darts and downward on horizontal ones. The darts guide shows the direction for each kind.
- Press every seam before you cross it. A side seam that is sewn before the waist seam is pressed first; a hem is pressed up before it is stitched. Once a seam is caught inside another, you cannot press it open any more.
How do you press without leaving marks on the right side?
The edges of seam allowances, hems and facings print through when they are pressed hard against a flat board. Three fixes: lay the seam over a seam roll so only the stitching line touches the iron; slip strips of brown paper or card between the allowance and the garment; and press lightly on the right side with the cloth, lifting as soon as the surface relaxes.
Shine comes from heat and pressure flattening the yarns. Dark wool, polyester and viscose shine first. The pressing cloth keeps the soleplate off the fabric, and a short press with steam, then a wooden clapper held down while the steam escapes, gives a crisp edge without shine on tailored seams.
What are the most common pressing mistakes?
- Pressing a seam open without pressing it flat first. The stitches stay on the surface and the seam looks rope-like from the right side.
- Ironing instead of pressing. The seam stretches, a neckline grows, a bias hem ripples.
- Pressing curves on a flat board. A princess seam or a sleeve head set flat will pull when worn.
- Too much heat for the fiber. Glazed polyester and scorched viscose do not recover.
- Pressing over pins. They leave dents and scratch the soleplate.
- Leaving it all to the end. Pressing after the garment is assembled reaches perhaps half of the seams. Press each one while it is still accessible.
- Moving the fabric while it is still warm. Fibers set as they cool; give each press ten seconds.
When should you press to one side instead of open?
Press open when both sides of the garment show, when the fabric is thick and would make a ridge, and on any seam that will be topstitched on both sides. Press to one side on knits (the allowances are narrow and the seam is often serged), on seams that will be topstitched on one side only, on yokes, waistbands and anything with an enclosed finish such as a French seam, whose allowances are already on one side by construction. A facing seam is pressed open first, then understitched with the allowances toward the facing, which is why it rolls to the inside and stays there.
Hems are a special case: press the fold line first, then press the allowance up, with strips of paper between the hem and the garment. The hemming guide covers hem depths by fabric.