I got a comment a while back asking for suggestions on the best way to calculate the proper length of fold over elastic. This made me think I should do a post on how I sew fold over elastic. And since my new yoga top uses this notion plenty, now is a good time to do a post about this topic. First a caveat though, this is not an area of expertise for me – I suspect for instance that lingerie making bloggers are much more proficient with this technique. But at least I can share how I do it!
Calculating the length
As with many things, this depends. But the general rule is that fold-over-elastic should be shorter than the garment measurements, unless the garment has some substantial negative ease already. Also how much shorter depends. If you are using it for, say, leg openings on a bathing suit, I think the elastic might be tighter than for a neckline or an arm opening on a regular garment.
When unsure, making a sample is your best friend. Since the bra I did for my yoga top already had negative ease (85% of my body measurements) after a few samples I came to the conclusion that the elastic should in fact be the exact same length as the pattern, i.e 85 percent. But since fabric tends to grow after cutting, the cut elastic ended up being shorter than the armholes and neckline on the actual garment, so I still had to stretch the elastic while sewing. This is a situation when fold over elastic really is a great option as it restores the original pattern measurements.
For comparison my bike cap has less negative ease and for that project the length of the elastic was about 95% of the pattern piece.
Evenly distribute the elastic
This is a super important step. I like to mark at least the half way point and sometimes also 1/4 and 3/4. So for the neckline mark the mid point on the fabric and elastic, match them up and stretch the elastic to fit. For a more extensive info on this topic, see my post about on how to sew ribbing.
Basting the elastic
Proficient sewists probably skips this step and just use needles or fingers while sewing, but for me I find that a quick basting saves me from a lot of pain later on. Having to rip zigzag stitches in delicate fabrics is not my idea of fun!
Sewing the elastic
A medium zigzag is what works best for fold over elastic in my opinion. For this top I used a 2 wide and 2.5 long stitch, which worked great. Stretch firmly while sewing, making sure the elastic is evenly distributed. Also because the elastic is stretched the actual finished zigzag will actually be bit tighter since it bounces back.
Also I prefer sewing the elastic on the flat. This means I first attach the elastic and then closes the side and shoulder/neckline seam. This give a little “bump” of seam allowance which might be unsightly, but I just topstitch it in place with the zigzag stitch. But you can also close the loop first and then use the basting technique.
The finished result
This is how the neckline looks after I attached the fold over elastic. Since there were several layers of fabric, plus gathers, I used a wider and slightly thicker fold over elastic to cover it all.