Hem

Fold, Fold Again, Sew Down

The hem exists because woven cloth has a weakness: a cut edge unravels. Threads at a raw edge have nothing holding them, and wear and washing pull them free one by one until the garment frays back from its own border. The classic hem solves this with geometry rather than extra material. The cut edge is folded up once, which turns the raw edge inward, and folded up again, which buries it completely inside the fold. Sewing down the fold then locks the whole arrangement: the edge that could ravel is enclosed in cloth on all sides, protected from friction and from the pull of loose threads. Every wearer has handled this construction a thousand times at the bottom of a trouser leg or the edge of a skirt without noticing it, which is the mark of a good hem — it is infrastructure, not decoration.

How the fold is secured divides hand work from machine work. A hem-stitch or blind-stitch catches only a thread or two of the outer cloth with each stitch, so from the outside the line of sewing is invisible; it is the finish expected on tailored and fine garments. A sewing machine sews a hem quickly and strongly, usually leaving a visible line of sewing, which casual garments accept as part of their look. Modern machines can make many decorative and functional stitches, so the number of possible hem treatments is large, and machines can also sew a reasonable facsimile of a hem-stitch — though the stitches will usually be larger and more visible, which is why most haute couture hems are still sewn by hand.

Other Ways to Finish an Edge

Because the purpose is preventing raveling, the term hem extends to every treatment that does that job. An edge can be serged on an overlock machine, which sews over the edge of one or two pieces of cloth for edging, hemming or seaming and usually cuts the edges clean as they are fed through — such machines are called sergers in North America. Delicate cloth can be hand rolled and then sewn down with tiny stitches, a finish still seen on fine handkerchiefs. Edges can be pinked with pinking shears, whose zigzag cut slows fraying, or covered with binding, which wraps the raw edge in a separate strip of fabric.

Weight changes the engineering. Heavy material with deep hems cannot hang all its weight from one line of stitching at the top of the fold, so a dressmaker's hem adds an extra line of loose running stitch in the middle of the hem to share the load. Hem depth itself is a design and alteration decision: a deep hem adds weight that helps a garment hang straight, and it leaves material in reserve so the garment can be let down later — the reason children's clothes and quality trousers are sold with generous hems. Hem, hemline and hemming are related but distinct terms: the hemline is where the garment ends, and the hem is the folded construction that finishes it there.