To sew Sirocco, you’ll need a knit fabric (jersey or interlock) with at least 60% stretch* and containing elastane. Elastane, which you can also find under the names lycra or spandex, is necessary for the fabric to spring back to its original shape after it has been stretched. It’s particularly important for Sirocco, as you put in on through the neckline: without elastane, the waistband would stretch as you wear it, the neckband would start gaping, and the knees and back of the jumpsuit would drop more and more as the day goes by. Be careful: stretch percentage is different from elastane percentage, and is measured directly from a swatch of fabric! Note that it is not necessary for Sirocco to have a 4-way stretch knit, only horizontal stretch, but if your fabric has 4-way stretch your jumpsuit will be even more comfortable 😉
Cotton-elastane jersey knit is the go-to choice for Sirocco, but for more structure you can also use interlock. Unlike jersey, which is knitted in a single layer and features a “v” pattern on the right side of the fabric and little waves on the wrong side, interlock is knitted in two layers and features the “v” pattern on both sides. Interlock knits, Ponte and Milano (which are two types of interlock originating from Italy) are thus heavier and thicker than jersey knits.
For a drapier result, consider blends containing rayon or wool, which add fluidity to the fabric. Avoid linen jersey however, as it won’t have enough body. In any case, aim for medium-weight fabrics rather than lightweight (at least 6oz. or 200g/m²), so you feel covered enough. And if you feel like experimenting, why not give stretch velvet a try for a wintery jumpsuit?
*If your fabric has less than 60% stretch but you want to use it to sew Sirocco, we suggest basting the left side of the jumpsuit on step 2-9 to try it on: if you have trouble pulling the waistband past your hips, you can insert an invisible zipper on that side to make it easier to put on.