Sewing with Cotton/Lycra Knits

Cotton/Lycra Knits: Comfort Meets Classic Design
Follow this designer's lead, and use simple techniques for utterly comfortable, great-looking garments
by Christine Jonson

Threads Magazine, Issue 89, July 2000, pgs 62-65

As a designer and patternmaker, I love working with cotton/Lycra knits, because they provide so many design possibilities that can be made with simplified construction techniques. I also love wearing cotton/Lycra garments like those shown here, because they fit well, look great, and are so comfortable.

I want to share what I have learned about sewing with Lycra knits, drawn from both my experience in creating ready-to-wear lines and, more recently, in developing my own pattern collection. The patterns are designed with Lycra knits unmanned, but the cutting, sewing, and pressing techniques I'll show you can be adapted to other patterns as well.

Choose a pattern that suits the fabric
Look for classic designs with clean lines–symmetrical or asymmetrical–that are shaped, but not tight. Jackets with slightly curved center back seams, shaped waistlines, and darted bodices are great, as are finger-tip-length straight and A-line shapes that give definition through the shoulders and neckline. Avoid boxy jackets, lots of details, high-cap sleeves, and linings. Choose skirt and pants patterns with darts or pleats for shaping, but eliminate zippers, interfaced waistbands, and side seams on pants.

Don't preshrink the fabric!
I know it goes totally against the grain to recommend not preshrinking cotton knits before cutting and sewing them, but trust me. Shrinking the garment with a steam iron during construction is the better alternative for cotton/Lycra knits, because this molds the shape into the garment, which can't be done if you preshrink the fabric. The challenge is to anticipate how the fabric will react to all this steam pressing and how much it will shrink.

The knit I use is a blend of 90% cotton and 10% Lycra, and I've found that it will shrink approximately 1 in. to 1 1/2 in. in length and 1/2 in. to 1 in. in width, depending on the garment. Other knits are available with more or less Lycra, from 2% to 35%, so its always best to test your fabric. Cut two 4-in. squares; press one with your iron on the highest setting using lots of steam until it stops shrinking, then compare it to the other unpressed swatch. You should notice about 1/8 in. to 1/4 in. of shrinkage. In my pattern line, I've taken this amount of shrinkage into consideration. However, if you're using other patterns, consider taking slightly smaller seam allowances and adding at least 1 1/2 in. to the length of a garment to accommodate the shrinkage. I don't think it warrants going up an entire size. I've tested some fabrics that have had as much as 3/4 in. of shrinkage per 4 in. square, though this is rare; and I would not recommend using fabric that shrinks this much because its quality is probably inferior.

Is there a right and a wrong side?
Cotton/Lycra knit fabric does have a right and a wrong side, but sometimes it's difficult to determine which is which. If you look at the fabric closely in good lighting, you'll see rib lines running parallel to the to the selvedge, and these lines are more pronounced on the fabric's right side. You check this by folding the fabric so you can see both right and wrong sides at once, then stretch both sides of the fabric, one at a time, against the grainline and look for the rib lines.

Try this approach to cutting
Cutting a pattern from cotton/Lycra knit fabric is simple and fast because the fabric is so stable and easy to handle. First cut out the pattern pieces along the cutting lines, cutting out any darts as well. Then instead of pinning the pattern pieces in place or using weights, lay them on the wrong side of a single thickness of fabric and hold each piece in place with your hand as you lightly trace around it with chalk (I use regular school chalk), tracing around the cut-out darts as well. I like this method because when I remove the tissue, I can see the garment sections outlined in chalk. Minor alterations, such as adding to a side seam or dropping the crotch, are easy to visualize, and I can do them by simply redrawing the chalk lines.

Once you've traced around all the pieces, fold the fabric with the chalked side up to create a double layer, and cut along the chalk lines through both thicknesses, using long, smooth scissor strokes. Cut out the darts about 1/4" in. inside of these lines to form a narrow seam allowance.

You'll need to interface collars and facings, so also cut the interfacing (I use a lightweight tricot knit) and fuse to the appropriate fabric pieces using lots of steam (this is the only case in which you should press before sewing). Applying the interfacing causes the fabric to shrink, so cut front facings 2 in. longer than the pattern (you can trim any excess later). Cut a collar 1/8 in. larger on all sides (my patterns are drafted with a slightly larger collar and longer front facings.