Bias tape is a lovely way to cleanly finished necklines on woven garments. They aren’t hard to sew, they just require some attention to detail and I’ll walk you through those details step by step! These same instructions can be used to finish any garment opening so if you are wondering how to sew an armhole with bias tape or how to sew a hem with bias tape, keep reading!
If the pattern you are using doesn’t have a template for your bias strip or instructions on how long to cut the bias tape, carefully measure the opening on your garment. Remember to measure on your seamline (which in this case will be 1/4″ in from the edge of the fabric) and not on the edge of your fabric. Use the very edge of your tape measure to measure the distance instead of laying it flat.
Cut your fabric the length of your opening + 3/4″ (since you need to account for the seam you will sew in it which will be 2 * 3/8″). The width of your bias tape is up to you, though do remember that the narrower that it is the easier it will be to sew smoothly around a curve. In this example (from the neckline of my Ultraviolet Tee) I’ve used 7/8″. Make sure you cut it on a 45 degree angle and don’t stretch it while you measure it.
For many projects, I recommend that you cut bias tape from your own fabric rather than use store bought bias tape. Store bought tape is quite stiff and on a lightweight fabric (such as challis, crepe, georgette, gauze, lawn, or voile) it’s important to use a lightweight bias fabric so the finished edge has the same gentle drape as the rest of the garment. On heavier, stiffer fabrics (such as quilting weight broadcloth or heavier) you can get away with the pre-formed bias tape, but you’ll still have a prettier result if you make your own.
Press one edge of the bias tape to the wrong side 1/4″. We do this now rather than later because it’s much easier to manipulate when the fabric is still flat on the table. If you have a hard time getting an accurate fold, you can make a template. In this example I’ve cut a strip of thin cardboard 5/8″ wide (the width the fabric will be after one edge is folded or 7/8″ – 1/4″). As you work with the bias fabric you want to make sure you aren’t stretching it out so handle it gently now and as you go along.
Sew the bias tape into a loop using a 3/8″ seam allowance (or a seam allowance that is half of whatever length you added when you cut the tape).
Press the joining seam open and then re-press the hem up over the seam.
Pin the bias tape to the neckline. If your tape and neckline lengths don’t match up then 1 – you measured wrong or forgot to add a seam allowance when you cut it, 2 – you have stretched your bias tape out while working with it so far, or 3 – you have stretched out the opening of your garment while working with it so far (i.e. you forgot to staystitch). For either 1 or 2, re-cut your bias tape and start over. For 3, write a big note that says “Staystitch!” to pin to your wall so you don’t forget next time. Then run a long stitch length seam just inside the edge of the fabric. The long stitch length may be enough to barely gather and stabilize your opening such that the bias tape fits. If not, gently gather the seam.
Sew the bias tape to the neckline. I suggest a 1/4″ seam allowance because much smaller makes it hard to sew at all and much larger makes it hard to sew the tape on smoothly.
Snip into your seam allowance all around the curve.
Press the bias tape and both seam allowances toward the center of the opening.
This is a reminder that this is a great place to use your tailor’s ham! (Don’t have one? Keep an eye out at thrift stores. I find nice vintage ones all the time.)
Understitch the tape by sewing a seam through the bias tape and both seam allowances very close to the seamline. Understitching helps fabric to roll toward a facing or lining so that when it is turned to the inside it is not visible.
Press the tape to the inside of the neckline.
Again, use your ham!
Sew the tape to the neckline close to the edge of the bias tape.
When you are done sewing you may see a few wrinkles but…
…give it a puff of steam and a quick press and it should lie perfectly flat!