Leggi questo post in: Italiano
Welcome to February 2017, which I am unofficially dubbing “Bias Month”! I was inspired by my newest sewing pattern to create a whole series of lessons and tutorials all about fabric bias for my Learn to Machine Sew course.
For a full list of the technical lessons and practical tutorials using fabric bias, click here for the Bias Month directory!
Now, you might be asking yourself:
What IS fabric bias?
As I explained in one of the very first Learn to Machine Sew lessons, “Understanding Fabric,” all fabric has a grain. The type of grain depends on the type of fabric, but most it’s pretty straightforward for most woven fabric. The straight grain runs parallel to the fabric selvedge and the cross grain runs perpendicular to the selvedge. If the fabric has no elastic fibers in it, woven fabric does NOT stretch along the grain and patterns are therefore usually cut along the grain to avoid distortion.
The bias grain runs in two directions at a 45° angle to the selvedge, and therefore also to the straight and cross grains.
Fabric can be cut along the bias for many different reasons. Let’s take them one by one.
Why use the fabric bias?
1. The bias is flexible and stretchy. Like I said before, woven fabric without any elastic fibers does not stretch even a millimeter. That is, unless, you use it along the bias. Bias tape, long folded strips of fabric cut on the bias, is frequently used in garment sewing to bind or hem curved edges because it has enough give to be worked around non-straight edges without any creasing or distortion. This is also the reason why neck ties are sewn on the bias; that way they can curve around the neck and be knotted smoothly.
We’ll talk more about bias tape later. This short video shows how just rotating a piece of fabric 45° changes the way it behaves:
2. Fabric cut on the bias doesn’t fray. Sure, tiny threads may come loose, but you’ll never see whole long threads come out.
3. Fabric cut on the bias drapes more nicely. Remember when I wrote about fabric drape? Very often women’s garments are cut and sewn on the bias so that they fall more fluidly around the curves of the body, often accentuating feminine curves. The following image from Sarah Image Fit shows some great examples of garments using the drapey quality of bias to their advantage.
4. Fabric cut on the bias can look really cool. This is often true in the case of fabric with a pattern. Stripes can be put together to create chevrons (like in the shirt in the image above), and other geometric designs can be juxtaposed, creating a really interesting aesthetic effect, as you can see below.
Cutting patterns on the grain or on the bias.
Pattern pieces, such as my soon-to-be released Field of Flowers costume shown in the following pictures, always have an arrow or line to show the grainline. This will usually be a vertical line, meaning that the pattern piece must be cut along the grain, which is the case of the Field of Flowers leaf.
When a piece needs to be cut along the bias, you’ll see that this line is at an angle, usually a 45° angle, which is the angle of greatest stretch and flexibility. This is the case in the Field of Flowers neck binding and strap piece, seen above.
When positioning the pattern pieces on the fabric, you must make sure that the grainline marking goes in the direction of the fabric’s straight or cross grain. Therefore a pattern that is to be cut along the bias will most likely need to be positioned diagonally across the fabric.
The one bad side to this is that you end up wasting some fabric because of the oblique positioning. As you can see above, there’s a lot more unused fabric with the Neck Binding and Strap piece positioned correctly than there would be if it were positioned along the grain.
Cutting bias strips from fabric.
Whole pattern pieces can be cut on the bias, but you will usually use bias in the form of bias tape, which are strips of fabric cut on the bias and folded lengthwise. Like I mentioned before, these are usually used for binding curved openings. I will show you in a later tutorial how to make very long strips of bias tape with or without a special bias tape maker, but for now I’ll show you how to make your own short strip of bias tape, just to understand how it works.
The cutting mat has a printed grid and also lines at various angles. The quilting rule also has a grid, so with these tools you can easily and quickly cut straight lines at a 45° angle whatever distance from each other that you want. Here’s how:
1. Position the edge of the fabric along the 45° line, as seen above.
2. Position the quilter’s rule so that the top edge is against one of the horizontal lines. In the picture above, I lined up with the 10 cm line. Cut across with the rotary cutter.
3. Move the quilter’s rule up however many centimeters width you need and make another cut. And there you have your bias strip!
Bias strips are generally folded into bias tape before sewing. There are two types of bias tape: single fold and double fold.
Single fold bias tape has the outer long edges folded in to the center of the fabric’s wrong side. The width of the bias tape is considered from one fold to the other. So if I fold both edges of the 6 cm wide strip that I just cut to the center, I will end up with 3 cm single fold bias tape. This type of bias tape is generally used for hemming or for simply sewing on top of fabric for decoration.
Double fold bias tape is single fold bias tape folded in half where the two fabric edges meet in the center, shown in the picture above. So my 6 cm wide bias strip, which was 3-cm single fold bias tape, would become 1.5-cm double fold bias tape. Double fold is used much more frequently, usually for binding curved edges, but it can be used in many ways, which I will talk about another day.
How to make double fold bias tape
1. Heat up your iron with the highest heat and steam settings possible and iron the bias strip flat.
2. Iron the strip in half lengthwise, wrong sides facing.
3. Open up the fold from step 2 and iron the top long edge down until it reaches the center fold. Do not go beyond the center fold!
4. Iron the bottom long edge until it almost reaches the center fold. The best double fold bias tape has one side that is ever so slightly wider than the other, just a millimeter or so. If this is too complicated, don’t worry about it, but it will make for more professional-looking binding, which we will get to in another lesson.
5. Fold the strip back in half along the original center fold and press flat.
That’s it! Notice in the picture above how one side of the double fold bias tape sticks out from under the other. That is because the second edge didn’t get folded all the way to the center in step 4.
Your double fold bias tape can be unfolded to show the wrong side of the fabric on the inside of the folds. The raw fabric edges are encased inside the folds.
If you need to make single fold bias tape, you just fold both raw long edges over by 1/4 of the strip width. So, in the case of a 4 cm wide strip, fold each long edge inwards by 1 cm for 2-cm single fold bias tape. This is really easy with the hemming trick that I showed in my How to Sew a Perfect Hem lesson.
Don’t forget to check out all the other lessons and projects in the Bias Month directory to use fabric bias to its best!
This lesson on fabric bias is part of the syllabus of Cucicucicoo’s Learn to Machine Sew beginner’s sewing course! Don’t forget to share pictures of your work on Facebook, Instagram or any other social media with the hashtags #cucicucicoo and #cucicucicoopatterns!