The Grain of Cloth: Three Directions, Three Different Materials

The SELVEDGE is the finished edge running down both sides of the cloth as it comes off the loom, and it runs parallel to the warp. That makes it the reference for everything else — the face side and face edge of a piece of cloth. The WARP (or lengthwise grain) runs parallel to the selvedge. The WEFT (or crosswise grain) runs from selvedge to selvedge. The BIAS is any diagonal, and TRUE bias is exactly 45 degrees to both. Test it by pulling. Tug along the selvedge and the cloth hardly moves; tug selvedge to selvedge and it gives a little; tug diagonally and it stretches noticeably and narrows as it does. Ten seconds with any scrap teaches this better than any diagram.

Cloth is often stored and sold off-grain — pulled skew on the bolt, so the weft is not at right angles to the selvedge. Cut a piece from it and the piece is born crooked. Find the true crosswise line by snipping the selvedge and TEARING across, or by pulling one weft thread out and cutting along the gap it leaves. Either gives a line that follows the weave rather than the edge of the bolt. If the two ends are not square to the selvedges, pull the cloth firmly on the bias in the opposite direction, or press it back square with steam. That is the same operation as tentering woollen cloth on a frame, done at a small scale.

Every pattern piece has an arrow. Lay the piece so that arrow is exactly parallel to the selvedge — measure from the arrow to the selvedge at both ends of the arrow and make the two measurements equal. Both ends is the whole technique. Eyeballing it gets you within a few degrees, and a few degrees on a trouser leg is a leg that spirals round the body over a day's wear. Pieces cut on the FOLD have the fold line marked instead, and that line must also lie on grain. A fold that is not on grain produces a piece that is not symmetrical, which is worse than merely being off-grain.

Cut a strip at 45 degrees and it will stretch round an outside curve and ease round an inside one without a single pleat. That is why a neckline is bound with bias strips, and why a straight strip put there ripples however carefully it is sewn. Bias also drapes. A bias-cut skirt falls in soft folds and follows the body because the cloth can extend where it needs to, which no amount of shaping on the straight grain reproduces. The cost is that bias grows. A bias-cut garment hangs and lengthens for a day or two before it settles, so it is left hanging before the hem is marked — and a hem marked immediately after cutting will be uneven by the time it is worn.