Sewing with Knit Fabrics
Knit fabrics are easy to sew and fit, require less pressing and care, and are comfortable to wear. Knit fabrics range from casual sweatshirt fleece to elegant stretch velvets and are available in a wide variety of fibers both natural and synthetic and a combination of the two. The degree of stretch varies from 20 to 35%. Select patterns which are designed for stretch knits only. These patterns require fabric that stretches a specific amount and the pattern envelope gives the degree of stretch.
Knit Fabric Types
Double knit is a firm, medium to heavy weight fabric which has fine ribs and usually looks the same on both sides.
Because the fabric has minimal stretch, patterns designed for woven fabric can also be used. Suitable for skirts, pants, jackets and dresses.
Sweatshirt fleece has minimal stretch, flat vertical ribs on right side and a brushed soft surface on the wrong side. Suitable for sweatshirts, pants, jackets, and other sporty garments.
Single knit fabrics and jersey knits are light to medium weight fabrics with flat vertical ribs on the right side and dominant horizontal lines on the wrong side. Fabric stretches from 20 to 25% across the grain. Suitable for T-shirts, tops, dresses, pull-on pants, shorts, skirts, and sleepwear.
Interlock is a light to medium weight fabric with a fine rib on both sides. Fabric stretches 25 to 35% across the grain. Suitable for tops, dresses, pull-on pants, shorts, skirts, and sleepwear.
Velour and stretch velvet are available in various weights. Velour and stretch velvet have a soft brushed nap on the right side, velvet has a shinner appearance than velour. Fabric stretches 25 to 35% or more across the grain. Suitable for tops, shirts, dresses, skirts, pull-on pants, and shorts and easy jackets.
Sweater and textured novelty knits are available in a variety of weights and textures. The degree of stretch varies. These knit fabrics are suitable for pull-over sweaters, cardigans, simple dresses and pull-on skirts.
Two way stretch fabrics are fabrics with Spandex/spandex and have approximately 75% stretch. Swimwear fabrics of Nylon/spandex usually have the most stretch on lengthwise grain, Cotton/spandex has most stretch on crosswise grain and is suitable for swimwear, activewear, dancewear, leotards and leggings.
Ribbing has approximately 100% crosswise stretch and has prominent vertical ribs on both sides. This stretch makes it suitable for neckbands, waistbands and cuffs. TIP: Do not pre-wash ribbing as it will be more difficult to sew.
Needles and Thread
Use a ball-point needle size 10/70 or 11/75 for lightweight fabrics, 12/80 for medium weight fabrics and 12/80 or 14/90 for heavyweight fabrics. Use an all purpose thread, polyester or cotton wrapped polyester.
Interfacing is used to reinforce closures, add shaping to collars, cuffs and plackets and stabilize areas such as shoulder seams and some necklines. The best interfacing is a 100% polyester fusible lightweight knit interfacing.
Purchase a little extra fabric, because most knits shrink to some degree. Wash the fabric in the same manner you intend to use for the finished garment. This will preshrink the fabric and remove the surface finish which will make it easier to sew.
Knits have shading and pattern pieces should be cut in one direction and be placed with the greatest degree of stretch around the body. Use weights to hold pattern pieces in place. A rotary cutter works very well with knits, just be sure to use a matt to protect your cutting table.
Seam allowances vary on patterns, the 1/4" (6 mm) seam allowance is the easiest to use.
Sew the seam using an overlock stitch. This stitch sews and overcast in one step. It is not necessary to stretch the fabric while sewing as stretch is built in.
The seam can also be done with a narrow zig-zag width and a medium stitch length. This seam will stretch with the fabric (Fig. 2). Overcast the seam allowances together with a larger zig-zag stitch or you can use a three step zig-zag stitch placing the stitches one right next to the other.
On a straight stitch machine, sew the seam using a medium stitch length; stretch the fabric in the front and in the back of the presser foot as you sew. Sew another seam on the seam allowance close to the raw edges to keep seam allowances together. If pattern allows for a 5/8" (1.5 cm) seam allowance, sew the seam, trim the seam allowances, and overcast the raw edges together.
On the Serger (overlock) machineuse three or four threads, guide fabric, being sure that the correct seam allowance is used.
Hems can be topstitched or blind hemmed. Sew the hem with a catchstitch by hand or use the blind hem on your machine. To topstitch hems, loosen the pressure on the presser foot to prevent the hem from stretching. Topstitch with a narrow zigzag and a medium stitch length, a double or a triple needle, or use the cover hem on the serger machine.
Stretch Chart and Gauge
To use the stretch chart or gauge, fold over the crosswise edge of
the knit fabric 3" (8 cm). Hold 4" (10 cm) of the folded fabric
against the chart and gently stretch to the outer line. If the fabric
stretches easily without excessive rolling to the outer line or
slightly farther, the fabric has the correct amount of stretch for the
pattern. this is an elastic seam.