I used my longest straight stitch (5.0, on my Bernina 730, but not sure exactly what 5.0 means. it might be millimeters of length?), I handwound my bobbin with elastic thread. (OH, if anyone else has a Bernina or an industrial, whatever, where you put your bobbin in a bobbin case, and THEN put it in your machine, you might need to loosen the screw on the case. At least, I did. when I just put the elastic thread bobbin in the case without loosening the tension on the case, the elastic broke right away, repeatedly, but as soon as I loosened it a bit, it went through just right. I think if I start shirring a lot, I'll invest in another bobbin case, cause it got annoying tightening and untightening the case as I switched back and forth between sewing and shirring)
This is my first attempt (luckily out of scrap fabric).
wrong bra and skirt, obviously, and too short for my taste (I'm thinking of adding a ruffle to the bottom, cause I really do like this fabric), but this was how long my scrap was, so...
It's only about 3 inches wider than I would have needed, unshirred, so that comes out to like x 1.1, instead of 1.5, but I really like it.
I think I might try it in super soft jersey next, (leftover from THIS dress).
As much as I LOVE this scrap (thanks Grandma!), I don't have any summer bottoms to go with it. Clearly I need to do more sewing.
BTW, the winner of the giveaway is commentor #1, Tien, so send me an email (lafamiliaburke (at) gmail (dot) com) with your address so I can send you your crochet thread!
thank you all so much for your advice!!!