To wear, sweater knits are my favourite for sweaters and cardigans. You get the look of a hand knit sweater, but you don’t actually have to knit it. And they come in so many varieties, fine or bulky, all acrylic, cotton or wool content, some even knit in a beautiful lace pattern or cables. They differ from jersey because they are usually knit more loosely and with thicker yarn. The variety of styles you can make is demonstrated in the Opal Cardigan sample garments, they are all knits but differ greatly in style. You can read more on picking the right fabric for your look here. Now, let’s focus on how to sew with sweater knits.
First off, a bulky, tightly knit fabric is the easiest to sew with. If it doesn’t have a lot of stretch you can almost treat it like a woven, including using a straight stitch and seam finishes. The tips below are meant for fabric knits that are more open and stretchy. I can say upfront that this kind of sweater knit is not the easiest fabric to sew with. But with these tips and a bit of practice you’ll have a cozy sweater or cardigan in no time!
Because of their stretchy nature, sweater knits can easily distort when you cut them out with scissors. To keep your fabric in place underneath the pattern, try using pattern weights and a rotary cutter.
Don’t snip your notches, as the fabric can stretch and unravel easily. Mark your notches by either a cutting a small triangle that sticks out or with a pin.
Handle your fabric with care during cutting and sewing. As long as the raw edges are not finished or secured in a seam they can stretch easily and distort the shape of the pattern piece.
A walking foot is your best friend when it comes to sweater knits. It prevents the fabric from stretching while you sew. If you don’t have a walking foot, lower the tension of the presser foot so the fabric can slide through the machine easily.
Feed the fabric through the machine without stretching it. Hold it up in front of the machine so the feed dogs don’t have to pull it up, and make sure the fabric on the left side of the foot moves at the same speed.
Use a ballpoint needle so you don’t pierce the fabric while sewing. A 70/11 for fine knits and an 80/12 for heavier knits.
Which stitch you use depends on which seam you are sewing. If it is a seam that hangs loose and is not under tension, you can use a slightly longer straight stitch, say 2.5 – 3.0. A longer stitch has more give than a small stitch. If the seam is under pressure, like armholes or other seams that go around your body, use a small zig zag stitch so the seam can stretch with the fabric.
For seams that are under a lot of pressure, or danger of stretching out while you don’t want them to, use something to reinforce them. The Opal Cardigan instructions tell you to reinforce the shoulder seams, the back neck seam and the pocket openings. Clear elastic is the most common for reinforcing seams. It’s almost invisible, stable and still stretches a little bit so the seam does not become rigid. You can also use stretch mesh or a strip of cotton jersey cut on the lengthwise grain. Both stabilise the seam without adding bulk.
Since most knit fabrics don’t fray, it is technically not necessary to finish the seams. It’s nice to do it anyway since a cardigan especially hangs open and the insides are visible. You can finish the raw edges with your serger or a zigzag. Test the seam finish on a scrap of fabric first. Be careful with your serger though, some are a bit rough and will stretch the fabric, making a wavy edge. Indiesew has a great post on how to prevent this.
You can press your seams like normal, but be careful when working with a spungy or textured knit. Too much steam and pressure can flatten the fabric. Use only the tip of your iron when pressing a textured knit.
You don’t have to iron the fabric, just the seams. Be careful not to distort the fabric while pressing, if you press it while it is stretched out it can stay stretched out.
Handwashing is the best way to go. Especially if your fabric has wool in it. Just let it soak in a cold bath with some gentle soap. Lay it flat to dry, hanging will distort the shape.
I hope these tips help you sew a beautiful sweater or cardigan! If you’re looking for the perfect fabric, check out this post where I list fabric shops that usually have a great selection of sweater knits. If you have a question, leave a comment.