Patterns designed for knits are labeled as Moderate Stretch Knits Only or Two-Way Stretch Knits Only. These types of garments often fit closely and do not rely on conventional zipper and button closures. Different knit fabrics have different amounts of stretch. Stable knits, which are those with the least amount of stretch, can often be used in patterns calling for woven fabrics. To determine the suitability of a knit for a particular pattern, it is important to use the stretch test found on the pattern envelope. To perform a stretch test, take a 4" (10cm) section of knit fabric away from the selvage and cut edges, and fold it in half. (Cut edges tend to stretch or curl, making it difficult to measure a knit’s stretchability.) Working with the crosswise stretch, lay the piece of knit on top of the stretch test measurement guide. Firmly hold the left hand edge of the knit against the pattern envelope while gently stretching the fabric. Did the right hand side of the knit stretch beyond the end of the measurement guide? How much did the knit stretch? Stable knits will stretch up to 1/2" (13mm), moderate stretch knits approximately 1-1/4" (3.2cm), super stretch knits 2" (5cm) or more, and two-way stretch knits a minimum of 2" (5cm) in both directions. After performing a stretch test, let the fabric relax. Does it quickly return to its original size? If not, your garment will stretch out of shape when worn. Knits that don’t “bounce back” are better suited for loose-fitting styles.

Have You Got the Notion?

As with any project, it is always important to choose the appropriate needles, threads, and other notions to achieve the best results. Universal sewing machine needles stitch well on most knit fabrics. Ballpoint needles have a rounded tip that eliminates snagging, and stretch needles avoid skipped stitches. All of these needles come in a variety of sizes from 60 to 90, suitable for everything from fine silk jersey to heavy, bulky sweater knits. Stretch twin needles come in various widths and are great for topstitching hems.

Use a good quality polyester thread for sewing seams in knits. The polyester has some give to it and helps to eliminate popped stitches. Be sure to wind your bobbin at a moderate, even speed to prevent the thread from stretching and creating puckered seams. Woolly nylon gives a nice soft edge when serging and can also be used in the bobbin when working with a twin needle.

Ballpoint and sharp, fine pins are best for securing a pattern to knit fabric. Rotary cutters make an easy job of cutting out knits, and eliminate movement and distortion. Narrow, clear elastic can be used to stabilize and retain shape in shoulder seams. Cotton twill tape will do the same job but it is best suited for seams that require no give at all. Stay-Tape® is a 1/2" (13mm) lightweight, nylon tape that will also stabilize seams.

The Inside Story

Many sewers think that interfacings are unnecessary when working with knits. However, there are areas in knit garments that need to be stabilized to prevent them from stretching too much and popping stitches. Interfacing is also used in some areas to give body and support. Tricot knit, Textured Weft®, and lightweight non-woven interfacings provide lengthwise stability and allow for some crosswise stretch. For knits that don't tolerate heat well, such as fleece, use a sew-in interfacing. Always test a good-sized swatch with your fabric first. Does it have the characteristics that you are looking for? For the most part, knit interfacings should maintain the fabric's drape and flexibility. Areas that may need more stability are hems, facings, waistbands, buttonholes, placket openings, zipper edges, pockets, collars, and cuffs. It is acceptable to use more than one type of interfacing in the same project. Choose the best type to suit the purpose.

The Cutting Edge

To make it easier to keep the fabric straight when cutting, work on a gridded cutting mat. Since knits are often made in tubes then cut apart, the selvage does not always provide a straight edge. To find a true grainline follow one of the ribs in the knit and form a folded edge along it. This is easier to do if the fabric is laid out with wrong sides together. (Tip: On some knits it is difficult to distinguish the right from the wrong side. Pull crosswise on a cut edge, the knit will curl towards the right side.) Many knits have a slight nap and should be cut using the with-nap layout. Others have a permanent pressed crease along the fold. Do not cut any pattern pieces along this fold, as this line will not come out. Instead, place the crease in the center of the table and bring the cut edges into the middle giving two folded edges. Avoid twisting, pulling or stretching the knit fabric as you lay out your pattern. On thicker, bulkier knits it is helpful to have your tissue pattern cut out first to prevent it from tearing as you cut. To maintain accuracy on thick fabrics, cut in a single layer.

Stitch Smarts

Sewing knits is fast and easy! Sergers are ideal for working with knits. A three- or four-thread serge stitch will give a quick, durable, professional finish to seams while maintaining stretch. A three-thread narrow serge stitch can be used on finer knits. Adjusting the differential feed on sergers prevents seams from stretching too much and becoming wavy, and the new cover stitch machines allow you to duplicate techniques found in ready-to-wear such as double-sided flat joined seams and flat hems.

If you are using a conventional sewing machine, several stitches are available for you to seam knits. A very slight zigzag set at .5mm width and 2mm length will resemble a slightly crooked straight stitch but gives knit seams built-in stretch. If using a second row of zigzag stitches, set the width at 3mm to 5mm depending on the weight of your fabric. Sew the edges together flat and then trim away seam allowances close to the stitching. For greater elasticity in seams, stitch length can be shortened slightly. Adjust settings to suit your fabric. Knits do not ravel and therefore, seams can be left unfinished. Some knits will curl—finish these seam allowances with either a wider zigzag stitch or one of the utility stretch or overlock stitches found on most machines. Utility stretch seam finishes can also be sewn flat and trimmed. For best results with the overlock stitch, trim seam allowances to 1/4" (6mm) and use the proper overlock foot for your machine to guide the raw edges along as it stitches over the edge of the fabric. Reducing the presser foot pressure slightly on soft, loose knits will prevent seams from stretching and waving.

Knit garments are often casual in style, making visible, topstitched hems a suitable finish. On fine, loose knits, let the garment hang overnight allowing the fabric to stretch slightly. If the knit tends to curl, interface the hem area with a lightweight tricot knit interfacing. Cover-stitch machines create beautiful hems with two or three rows of topstitching on the right side and a cover stitch on the bottom. Top and bottom cover stitching is also available, providing a more decorative finish when using novelty or contrasting thread. Stretch twin needles, in widths of 2.5mm and 4mm are perfect for finishing hems on a conventional sewing machine. Two rows of topstitching on the right side with a row of zigzag on the bobbin side give knits the stretch they require. Lengthen the stitch slightly for a nice finish. To hem dressier, stable knits, a machine blindstitch can be used.

Closing Time

Zippers and buttonholes are both suitable closures for knits. Stabilize zipper seam allowances and buttonhole areas first with interfacing. Strips of 1/2" (13mm) tricot knit interfacing cut on the lengthwise grain will help to prevent zipper openings from rippling. For buttonholes, the lengthwise grain of interfacing should run parallel to the direction of the buttonhole. A corded buttonhole made with topstitching thread or a perle yarn No. 8 will reinforce buttonholes on knits. Some machines have stretch buttonholes. Alternately, lengthen the stitch of a regular buttonhole to keep the stitches moving along.