Bias Tape
Bias tape is a narrow tape made by cutting woven fabric on the bias, diagonally to the grain, so that it easily covers curved edges.
Definition and Overview
Bias tape is a narrow strip of fabric cut on the bias, generally at a 45-degree angle to the warp and weft of the woven fabric. Even if the fabric itself does not have much stretch, it is easier to stretch diagonally, so it conforms well to curved edges.
It is used to finish raw edges such as necklines, armholes, hems, and pocket openings by encasing them, and it is also used for decorative color accents. By covering the cut edge, it helps prevent fraying while giving the seam allowance a neat finish.
Materials and Structure
Most are made from woven fabrics such as cotton or polyester, and plain-weave textile is commonly used. Depending on the material, thread thickness, weave density, and finishing process, softness, thickness, sheen, ease of sewing, and shrinkage after washing will differ.
Bias tape shapes include raw cut strips, single-fold tape with a crease on one or both sides, and double-fold tape folded in half at the center. Double-fold tape makes it easier to enclose fabric edges, while single-fold tape is used for finishing seam allowances and facing-side finishing.
Knit tape or stretch tape is sometimes also called bias tape, but the original meaning refers to woven tape cut on the bias. Where stretch is needed, it is important to check the material and structure individually.
How Width Is Indicated
Width may be shown as the full width before folding or as the finished width visible after folding. Even with the same listed width, the amount of fabric that can be enclosed and the appearance will vary depending on the folding specification, so check the specification drawing or the actual product.
When selecting, base your choice not only on the tape width but also on the thickness of the fabric to be enclosed, the seam allowance, and the width you want visible on the outside after sewing. When enclosing thick fabric or overlap sections, confirm with a sample whether the folded-in amount of the tape is sufficient.
- For single-fold tape, consider the seam allowance finishing method based on the folded-edge side.
- For double-fold tape, the fold widths on the front and back are not always the same, so check the side that will be sewn in.
- Estimate the required length by allowing for the fit around curved sections and enough margin for edge finishing.
Main Applications and How to Choose
Bias tape is used for piping-like finishing on woven necklines and armholes, edging aprons and accessories, and finishing seam allowances on the inside. It is advantageous in areas with many curves because it conforms more easily than straight-grain tape cut straight.
For applications where it will be visible on the outside, match the color, sheen, thickness, and post-wash appearance with the main fabric. For necklines and armholes that touch the skin, also check stiffness and the feel of the edge. For inside finishing, choosing a tape that is not thicker than the main fabric makes it easier to reduce bulk at the seam allowance.
Handling and Differences from Similar Terms
Because the bias direction stretches easily, pulling strongly during sewing can cause waviness and dimensional inconsistency. On curves, do not force the tape to stretch; sew while easing it in as needed. Before sewing, it is safer to check sewing shrinkage, color bleeding, and shrinkage after washing using a scrap piece.
Raw-edge bias tape may fray at the ends, so consider edge finishing and the sewing position. Binder tape and binding tape are broad terms for applications and sewing methods, and they do not always refer to woven tape cut on the bias.
Half-bias tape refers to tape cut at an angle other than the standard 45 degrees even though it is on the bias direction. Since its stretch and conformity to curves differ, do not substitute it with regular bias tape as if it were the same.
Frequently Asked Questions
How do you choose between bias tape and straight tape?
For curved necklines, armholes, and round pocket openings, bias tape that stretches diagonally and conforms easily is suitable. For straight sections and areas where you want to limit stretch, straight-grain tape aligned with the grain is often chosen.
How can waviness in bias tape be prevented?
When sewing, the basic rule is not to pull only the tape or only the main fabric, but to place it evenly along the curve. Before sewing, do a test stitch and adjust the presser foot pressure, stitch length, and the combination of tape width and fabric thickness.
