Fact: sewing beginners often don’t know what “bias” exactly stands for…
I’ve decided to write about it after receiving some question like:
– What does “cut on the bias” mean? –
– How can I cut on bias a rectangular shape, having its measures? –
– How can I lay a pattern piece on bias? –
A frequent beginner sewist’s mistake is simply to ignore how the fabric is made and how its properties changes, depending on your pattern’s direction line-up.
If you’re completely unfamiliar with fabric, I’d suggest you read my Fabric 101 post, where I’m explaining what a straight grain, cross grain and a bias are.
Today’s main dish is:
First of all, according to with Wikipedia, let’s see what does bias (on textiles, at least…) mean:
The bias direction of a piece of woven fabric, usually referred to simply as “the bias”, is at 45 degrees to its warp and weft threads. Every piece of woven fabric has two biases, perpendicular to each other. Non-woven fabrics such as felt or (non-woven) interfacing do not have a bias.
Wha-wha-what’s? Ok, better put in an explaining pic:
Now, maybe you’re thinking:
“I have so many things to look at and learn, as a beginner! Couldn’t I skip this bias thing and cut randomly? Isn’t it the same?”
The short answer is: “No, you shouldn’t!”
The long answer is: “Absolutely no! Go on reading and you’ll know why!”
Remember that the same fabric, cut on grain or on the bias, has completely different properties!
If you cut it on the bias, your fabric will be:
- slightly elastic
- smoothly draping
- more supple
- not fraying
- thinner (or at least it seems to be!)
- Consider carefully all bias properties listed above while deciding if cut a pattern piece in bias or in grain, because sometimes you’ll need to stabilize a bias-cut fabric to avoid annoying wrinkles and bumps (as if buttons/buttonholes and/or zippers, or pockets are involved);
- When a pattern(maker) asks you to cut a piece on the bias, often it’s because this particular piece has to drape softly or stretch just a little. If you ignore this, you could end with a completely different result from what’s shown on your pattern’s cover!
- A pattern cut on the bias is often designed without darts, because it takes advantage of your bias-cut fabric’s natural stretch to add ease and fit well: cutting on grain will likely leave you with a garment you can’t wear at all!
- A negative side-effect of bias-cut is that it literally eats more fabric: yardages needed are usually way bigger than traditional grain-cut patterns and leaves you with much more scraps (that, if you are like me, you’ll end piling here and there, just in case – never throw out anything!!!)
- Try this awesome Sandra Betzina’s Craftsy class, to learn even more bias secrets!
Ok, let’s go practically! Here are my
best tips for sewing with bias-cut fabric:
Never. Pull. Fabric. I mean Never!!!
…or it will lose its shape: allow the pattern piece to keep its natural shape!
Remember that a fabric cut on the bias is more elastic than the same fabric cut on grain, so, when you pull it, it extends:
Can you see how much it stretches, along the bias?
To stay on the safe side, simply add staystitching along the edges (remember: sew inside your seam allowances!), just after cutting your pattern pieces, and carefully sew without stretching!
Let’s take a look at the same bias-cut scrap of fabric, after staystitching it:
Look how much less flexible is now!
When sewing bias-cut fabrics, better sew little portions of your seams, stop and repeat: this will help you avoid pulling, therefore, distorting your pattern piece.
Press seams without sliding your iron on your bias-cut garment surface.
You’re right, this is a rule of thumb for any press-while-you-sew advice, but on the bias is mandatory, or you’ll certainly end with a distorted pattern piece, no more matching with the other pieces of your pattern (it could be longer, shorter or simply morphed in shape).
How do I hem a bias-cut garment?
Let it on a hanger (or better on a dress form, if you’re so lucky to have one!) a day or two before hemming it.
This is the only way: leave it alone, it will “sit” and relax (a cup of tea?) and finally have a nice straight hem on your bias-cut garment
If you skip this step, your hem will be uneven, with a potentially unwanted (and completely random) hi-low effect!
Stabilize seam allowances, when needed
Use a lightweight woven fusible interfacing (cut on grain!) if you have to add a zipper on edges of a bias-cut garment (often a skirt or a dress, but could be a blouse too!); some hand basting can also help you avoiding ripple marks – do not skip it here!
Stabilize when adding buttons
If you’re going to add buttons and buttonholes on a bias-cut garment, stabilize it adding interfacing scraps behind them.
If you have a woven interfacing (my favorite, I don’t like non-woven kind!), cut it in grain and not in bias, or your pattern piece will stretch also if interfaced!
Save time on finishing seam allowances, since bias doesn’t fray!
If you like, you can trim off some of the seam allowances bulk, using pinking shears.
What if I have to sew together a bias-cut piece to a grain-cut piece?
Always put the bias piece right above the feed dog and the other one on top, against the presser foot: the bottom layer will be eased in while the top (on grain) layer will help stabilize the seam!
Look at your fabric closely before cutting!
Consider adding a central seam on a bias-cut garment’s front and back pieces: if your fabric’s crosswise and lengthwise threads looks quite unequally distributed, add it!
The two bias directions often don’t drape similarly (depending if it’s crosswise or lengthwise threads on up-down direction) and you could end with a crooked garment! Better add a central seam (and if you’re using a striped fabric you’ll have a free chevron shape!!)