Bias tape is a strip of woven fabric cut on the diagonal grain. At approximately 45 degrees to warp and weft, the cloth can shape more readily than it can on straight grain. This allows the tape to follow necklines, armholes, and other curves without immediately forming tucks along its outer edge.
Bias-tape folds
- Flat bias strip: supplied or cut without pressed folds
- Single-fold bias tape: both long raw edges are pressed toward the centre
- Double-fold bias tape: single-fold tape is folded again so it can wrap a raw edge
Retail names and measurements vary. Check whether the stated width refers to the strip before folding or to the finished folded tape.
Making continuous tape
Cut strips at a true 45-degree angle to the selvage. Join short strips with diagonal seams so the seam allowances are spread along the length rather than stacked across one line. Trim and press those seams open before using a bias-tape maker or pressing the folds manually.
Binding and facing edges
In a visible bias binding, the tape wraps around the raw edge and the final stitching catches both sides. In a bias facing, the strip is turned completely to the inside, leaving only understitching or topstitching visible from the exterior.
Do not stretch bias tape indiscriminately while attaching it. An inside curve needs the outer edge of the tape to accommodate more length, while an outside curve needs flexibility on the inner edge. Shaping with steam and pinning or basting in short sections helps prevent puckers and drag lines.