Bias

Definition and Overview

Bias refers to the diagonal direction relative to the warp and weft of woven fabric. In particular, the direction at roughly 45 degrees to the warp or weft is called true bias, and it is used for cutting garments and making bias tape.

Woven fabric is usually easier to stretch in the bias direction than in the warp or weft direction, and it also tends to conform more easily to curves. This property is used to create a better fit to the body and a drapey appearance.

Characteristics

When cut on the bias, moderate stretch can be obtained through diagonal distortion even if the textile itself does not contain stretch material. A key feature is that it follows body movement more easily and tends to create a soft drape.

On the other hand, the bias direction is more likely to stretch or change shape when pulled, and dimensions may become unstable during cutting and sewing. For patterned fabrics, attention is also needed because the appearance of the pattern changes diagonally.

Main Applications

Bias cutting is used for dresses, skirts, blouses, camisoles, and other items that make use of drape. Bias tape used to bind curved areas such as necklines and armholes is also a typical application that makes use of diagonal stretch.

For finishing textile edges, bias tape is useful because it follows curves easily. However, where reinforcement of straight sections or control of stretch is needed, tape cut on the grain may be chosen.

• Edge binding and piping for curves
• Facing and finishing for necklines and armholes
• Garment bodices and skirts that make use of drape
• Tape-like parts that conform to stretch

Selection and Handling Notes

When adopting bias cutting, check the weave structure, thickness, drape, and diagonal stretch of the textile in advance. Thin textiles, slippery textiles, and easily stretching textiles are prone to losing shape, so straightening the grain before cutting and allowing sufficient yardage are important.

In sewing, there is a method of hanging the cut parts to let them settle before adjusting the length. For areas where seams are likely to stretch, use stretch-stabilizing tape or interfacing as needed, and avoid pulling the textile strongly while sewing.

Because washing or steaming may change the shape, perform wash tests and sewing tests before full production to check for shrinkage, stretching, and seam waviness. Parts cut on the bias should also be protected from hanging stretch during storage.

Differences from Similar Terms

Grainline refers to the direction of the warp and weft in woven fabric and the standard used for cutting along that direction. Bias is the diagonal direction relative to the grainline, and the two are opposite concepts as cutting directions.

Bias tape is a narrow fabric tape cut on the bias. Bias refers to the direction or cutting method itself, while bias tape refers to a supplementary material or part that uses that property. Half bias may refer to a shallower diagonal direction than true bias, but usage and angle handling vary by workplace.

Frequently Asked Questions