Once upon a time, if you wanted to make yourself a sweater, you needed to learn how to knit. These days, sweater knit fabrics are readily available both online and in local fabric stores, giving you the option to sew sweaters, as well as skirts, dresses, and more. Because most sweater knits are soft and very stretchy, they can be difficult to sew with, especially if you don’t know what you need to do differently than when sewing on other types of fabric. For great results (and less frustration!) follow these 7 easy tips for how to sew sweater knits.
1. Be sure to prewash your material however you plan to wash the finished garment. Many sweater knits come with a hand wash and lay flat to dry recommendation, so do that first if that’s how you’ll plan to treat the finished garment. If you’re lazy, like me, and just want to be able to wash and dry your clothes by machine, wash and dry the fabric before you get started, realizing you’re taking your chances (be sure not to put a wool sweater knit in the dryer!).
2. Use the right needle. As with other knit (stretchy) fabrics, it’s a good idea to use a ball point needle. These needles push fibers apart and go between them instead of poking holes through the fibers. Ball point needles are easy to find at any sewing store, and come in different weights to correspond the weight of the fabric you’re sewing. Pick a smaller number (like 9) for delicate sweater knits and a higher number (14) for heavy sweater knits.
3. Use a stitch that will stretch. Anytime you sew on stretchy fabrics, your stitch must be able to stretch as well, or you’ll end up with popped seams once the garment is worn. Many sewing machines have a stretch stitch, which often looks like a lightning bolt, that is specifically made for sewing on knit materials. You can also use a zig zag stitch, a double needle, or even a standard serger stitch, as those stitches will all allow for some stretch.
4. Avoid stretching out the material as you sew. The single most frustrating thing about sewing with sweater knits is the tendency to end up with wonky stretched out seams, like the one you see below on the left.
To get a nice, flat seam like the one on the right, try these tips:
- Lengthen your stitch length. A short stitch length almost always stretches out the fabric as you sew.
- Don’t sew too close to the edge of the fabric, or it will get chewed up. Try cutting out your pattern with extra seam allowance so you can stay at least 5/8 inch away from the edge.
- Use a walking foot (often called an even feed foot).
- Up the differential feed setting on your machine (check your manual to find out where to do this). This causes the machine to feed the material under the presser foot faster, which can prevent stretched out seams.
- Decrease the pressure on the presser foot (only available on nicer machines).
- Sew a little faster. This may seems counter-intuitive, but sometimes going a little faster helps the machine feed the material more evenly.
- Be sure the material is not getting stretched out in front of the machine. Try using your fingers to gently push it under the pressure foot as you sew, and NEVER pull it from behind the presser foot.
- Use a lot of steam to help shrink stretched seams back into place.
- If all else fails, you can place a piece of tissue paper under the material as you sew to help it feed more evenly. I don’t love doing this, as you have to pick the tissue paper out of the seam afterward, but it works as a last resort.
5. Finish raw edges if needed on sweater knits that tend to fray easily. Unlike other knit fabric, most sweater knits will fray. If you have a serger, it will automatically finish the raw edges as you sew. If you don’t have a serger, try a “double zigzag” approach. Cut out your pattern pieces with extra seam allowance. Sew the seams with a narrow zigzag, then sew a wider zigzag down the middle of the seam allowance. Trim close to the wide zigzag and press the seam allowance to one side.
6. Consider reinforcing shoulder seams or any other seams that will get quite a bit of stress. I generally sew clear elastic right into the shoulder seams to keep them from getting stretched out and misshapen, especially when I’m using a lightweight or very stretchy sweater knit (you can usually skip this step if you’re sewing on a very stable knit). Don’t iron directly on the clear elastic though – it’s very easy to melt it.
7. Hem using a double needle or hem band. You may zigzag the hem, but a double needle looks MUCH more professional and is so easy to use (just google a tutorial). A double needle hem looks like this:
Alternately, many sweaters are finished with a hem band, which looks like this:
You can find more directions on using a hem band in the easy tee post.