Bias Binding

What is bias? Strictly, it’s the diagonal direction on a woven fabric.
As commonly used, the stretchiest direction of fabric.

On grain, a firmly-woven fabric will stretch slightly; cross grain a little extra. Bias has considerably more give, comparable to cross-grain on most knits. “For bias strips from a knit, cut them crossgrain” is technically incorrect but a common direction.

For the rabbit hole of designing garments cut on the bias for fluid drape, start with the couture designer Vionnet (Wikipedia link).

This tutorial is about binding edges with bias. They do not fray, either in woven or knit, so can be used in very narrow strips.

Bias tape: bulk put-up and commercial packages in standard width (others are available). Note that the prefolded is asymmetric, so that it can be sewn as in example C below.

The sewing machine attachment is useful for either flat or folded. Fiddly to feed the tape through (I do that before attaching to the needle bar), but then it’s sewn in one pass. Plan on a practice run, to get used to feeding the fabric into the tape fold. Not shown in the examples below.

Bias strips easily stretch out, so handing them carefully is more than half the battle.

Stay-stitch your garment’s raw edges slightly inside the future seam lines (closer to the raw edge) before starting to assemble it. The stay-stitching is shown as lighter thread though it would be the same as you use for the rest.

For making your own bias tape, first determine the width you’ll need – it’s significantly greater than what you’d think due to TOC – “ turn of the cloth”. That’s the extra that wraps around the flat bits: in a standard bias binding, a full extra seam allowance’s worth.

Replace above graphic

How do you calculate it?
Hands-on. It will vary almost every time unless you’re doing a mini-production run of, say, half a dozen shirts.

You should have roughly laid out BUT NOT YET CUT your pattern. Make a smallish mock-up from an odd chunk with all the layers. If a piece has interfacing, that must be in your sample.

I like to use long, flat-head quilter’s pins. Chalk (it can smudge off) or washable (or permanent!) markers, or, if you’re feeling upscale couture, a contrast basting thread. La.

Mark the starting point. Roll or fold into place, mark exactly where the far end falls, undo and measure.

We have gained an entire seam allowance’s worth. This would be less on a lightweight silk, and more if denim.

Above: quick sketch showing all pattern pieces, to be circled as they are made. Below: all bias pieces stacked together in a rectangle. They could be slipped sideways into a parallelogram if that would make the layout easier. Don’t bother to stairstep the short ends, just be sure the needed length is there and cut it straight.
To prevent stretching, they should not be cut into individual strips until ready to sew.

Pattern pieces for a shirt roughly laid out, with the block of staggered bias strips on the true bias.

Four tank tops for my sister on three opened-flat layers of silk charmeuse, ready for their final pinning and stack cutting. The bias was shiny-side-out and the tops were reversible so she could opt for shiny-on-shiny or shiny-on matte.

Cutting bias in bulk:

Suppose you found some lovely lightweight blouse fabric that you want to turn into bias for the future? This should be done at the top of your game. If you aren’t feeling like you can be precise, set it aside for another time. It’s too much work to lose to sloppiness (I have made all the mistakes for you).
You’ve done a sample test to know its width.
What doesn’t work is to fold your yardage in half and cut diagonals: you’ll get big Vs with the center chunk unusable.
Instead, take a length of pattern paper and draw correctly-spaced lines on it.
Pin the strips onto the top corner of your fabric – hope you pre-shrunk it!
Cut right at the edges of your paper.
Lift down and align with the cut edge of your yardage.
Re-pin.
Lather, rinse, repeat, re-pinning each time you shift the sandwich.
Only now do you cut apart the strips (if you can spare the pins, leave them in until ready to sew).

The right-hand photo shows strips loosely rolled and held with the little widgets from a tagging gun, such as are used to put price tags on garments.

Two weights of bias tricot: the first a roll from a lingerie factory, the second strips I hand-cut.

Couture bias-binds the seams of sheer blouses with skin-colored silk (I’ve seen photos). Claire Shaeffer told of a woman who was loaning one of her gowns to a friend, and sent her in for slight alterations. They said, certainly, madame, no problem (and no charge) but it will take slightly longer as we need to redo the seam binding. Her friend had much darker skin.

When I ran across this sheer nylon tricot in my skin shade, I bought a couple yards and cut it into bias strips. I may never use it for another sheer blouse, but it’s come in handy several times for other projects.

It’s a good idea to piece your bias strips now. “How?” You ask.

Bias binding’s seams are sewn on- or cross-grain (so they appear as a 45° angle rather than straight across) for stability.

The strips’ short edges will always fall to maximize wastage. You will learn to get past it.

1. Strips to be sewn
2. Flip right-hand strip over and sew exactly from raw edge to raw edge. Press. Trim, press.
3. Right side
4. Wrong side

Types of bias binding:

A. Set up for all of the following:
1. Right sides together, sew bias to edge of garment. Press. 
2. Gently but completely fold bias to the side over the seam allowances. Press. 

B. Hong Kong Finish, popularized by the tailors there as it was a fast and light-weight finish for tropical suits and other 
garments. The raw edge of the bias is usually hidden and will not fray. It’s more supple and less bulky than the following two treatments.
1. Wrap the flap around the seam allowances to the back. Press. 
2. From the right side, stitch in-the-ditch with a short stitch length. Press.

C. Machine sewn 
1. Wrap the bias around the seam allowances and fold it back on itself so that the back fold is wider than the front. This is what you get if you buy commercial stuff.
Press.
2. Stitch in the ditch from the right side, going slowly and feeling that the underside is laying correctly. Press. If the inside stitching is off a bit, as long as it catches the fold, it won’t show and is okay.

D. Couture, finished by hand 
1. Wrap the bias around the seam allowances and fold it back on itself to barely cover the machine stitching. Press.
2. Slip-stitch the fold from the wrong side. Press.

Applying bias strips

For the armscye strips, key (quickly hand-baste*) a couple lines across before sewing the first. This lets you adapt the second strip into its loop before applying it.

* or chalk – the advantage of thread is that it shows from both sides and won’t smudge off

1. Begin binding a neckline with the top inside out. Sew the bias strip’s right side to the right side of the top starting a finger’s length behind the back shoulder seam. Place a pin at the exact start of the stitching. Stretch the bias slightly as you apply it (if you under- or over-shoot, take it out and re-do it).
2. End at the same point. Do not catch a fold of the strip where you started.

the diagonal seaming, than adjusting the second strip

1. 
   Trim and press flat.
2. Turn top right side out. Fold bias to the wrong side and finish with one of the methods shown below. If the inside stitching is off a bit, as long as it catches the fold, it won’t show and is okay.

Binding a V-neck

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The old solution to knit edges rolling was spray starch.

The trade-off is that It may get sticky as you’re manipulating stuff. But it’s easy to wipe down the bed of your machine after (likewise grubby hands).

Wash it out after.

You can get it quite stiff (hurr). You may need to de-crud your needle too (a wet Q-tip works). When I had to sew flimsy tricot* the spray starch meant its own set of fussing, but it was far preferable to the damned stuff rolling and distorting.

Over-the-top couture treatment for sheer fabrics: use the narrowest bias* binding of whisper-weight silk (crepe de chine or chiffon) as a seam finish (on the inside). This is among the most fiddly types of hand work. Kiss your loved ones goodbye and enter an alternate reality of taking plenty of time.

If your binding matches your skin tone, your seams will not shadow through to the outside. I have substituted extremely light nylon tricot as it’s hard to find the right color silk.

While the lingerie-weight stuff will work, the sheer is better (it will be doubled on each side of your main fabric). Find it from bra suppliers or costume houses (think ballet/dance/figure skating)

* “bias” meaning whichever direction gives the most stretch. With a knit tricot, it’s usually cross-grain.

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Binding tilting out/not lying flat means the strips are too long, so you can reuse what you have for the nuisance of picking out its stitching. It’s worth taking the trouble to key your armscye strips – baste across your best guess, then after the first one is on, you’ll know what you need for the second.

There isn’t any magic formula, either. It usually takes me two or three tries of hand-basting to get the tension right.

A beautiful bias edging is worth it, IMHO. We made several of these mock-wrap tops for arayti, and the binding lengths were different for all of them. I did the first, talked her through the second, and stood by while she did a couple more.

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Casings: this is the method I’d use, as folding up and stitching a self-casing can be a challenge (and as aerieiris noted, can drastically shorten the garment). This also saves your ass if the garments are in play for years and the elastic needs to be replaced.

Sew strips across the width that only go across one seam: mark the inside of the fabric where the casings will go, sew one side seam, sew the casings completely around over one side and stop short of the other. The elastic isn’t going to go anywhere across the unsewn bits.

If you’re using self-fabric that ravels, yeah, you’re going to need to control the edges. I have a serger so I’d use that. Or zigzag. Or turn the edges under.

Wider bias tape would work (now available due to the need for masks*). Blanket binding might be too heavy. Strips of any light knit wouldn’t ravel: swim suit lining would be great.

For the sleeve pictured, I’d put a piece across the entire sleeve and run the elastic where you want it. This will add bulk, so much as a sleeve head supports the cap, it will help hold out the sleeve between the bands.