Working with knits – the sewing process

Sewing with knitted fabrics can be freeing although it is occasionally frustrating.  It is freeing because knits like Spandex are so forgiving and very little fitting is needed, and the seams don’t need finishing.  It can be frustrating if you don’t use the right tools and techniques when working with them.  This blog will give you an overview of how to sew with knits so that the frustration is lifted and you can be free to enjoy sewing these comfortable fabrics as much as you enjoy wearing them. (check out my previous blog for information on choosing fabric and laying out the pattern)

The tools:

Ballpoint sewing machine needles are a must, especially when sewing through elastic.

Fine, long straight pins are much easier to work with and don’t stick to the fabric.

A machine with a zigzag stitch and/ or a serger is best. A coverstitch machine is sweet but not essential.

For cutting knits I prefer a cutting wheel, but have used serrated scissors in the past (before the Olfa wheel was introduced). Regular scissors don’t work well as the knit has a tendency to slip and stretch whereas; the serrated edge holds the fabric against the cutting blade.

Pattern weights make cutting out faster.

A toothed tracing wheel works better than the smooth blade as the fabric tends to be thick.

Beyond this list, you can use pretty much what you already have in your sewing room. Make sure your thread matches your fabric type and not just the colour, i.e. use polyester thread for synthetics.

The method:  Set your stitch length at 3-4 mm.  3mm is best for most garment weights, but you’ll need longer stitches for heavy fabrics like fleece.

Adjust the tension for the weight of the fabric as you would for a woven. (Tension adjustments are unique to every machine, so follow your manual on this.)  Always stretch as you sew with a straight stitch, even when basting.  Play with this on sample pieces until you’re comfortable with how much you have to pull on the fabric to get a seam that gives, does not pucker and maintains its shape.  You should have one hand behind the needle and one in front keeping a steady tension and allowing your machine to pull the fabric through.  If the seam appears stretched, you have put too much tension on your fabric and there is too much thread in the seam to allow the knit to relax back to its original shape.  If it puckers, you haven’t got enough tension on the fabric and the seam will break when you try to stretch it.

Once the fit is right, serge the seams to give a ¼” seam allowance and a stretchy seam.  If you are using blanket fleece serging just adds more thread to the already bulky seam and you don’t really need to finish the seam allowance.

Pressing knits should be done carefully and as little as possible as the fabric can stretch out of shape if worked too hard – or melt if the iron is too hot!  Very often finger pressing is sufficient while sewing, especially on Spandex. Use a warm iron and steam and just touch the tip of the iron if possible.

Use a stretchable iron-on interfacing if it is required. You will want to maintain the soft feel of the knit even in a collar or cuff, so choose the weight of the interfacing accordingly.

Heming can be done by machine with a zigzag hem stitch or top stitch, twin needle top stitching or by using a two or three needle coverstitch.  The coverstitch is used on most ready-to-wear tops and dresses. Whichever method you choose, keep in mind that the hem needs to stretch.

I hope this short lesson helps you with your next project. As always your comments and questions are welcome.


Working with knits – getting started.

Knitted fabrics come in all weights and textures and need to be handled according to their individual characteristics. Before cutting into the fabric you should experiment a bit to see how it reacts to things like stretching the cut edge, pressing, washing and foremost how much stretch it has.  The pattern you intend to use will tell you how much stretch the fabric needs as a percentage and can be from 10-25% or more.

To determine the amount of stretch, hold 10 cm of fabric across the grain and stretch it as far as it will go. If it goes to 12.5 cm then you have 25% stretch (2.5/10= 25%). Is it 2-way stretch or 4-way stretch (across the grain and with the grain like a bathing suit)?

If you plan on washing and drying the finished garment, then wash and dry the fabric before cutting. I like to do this step with all my fabrics regardless of the weave.

Press a small area of the fabric with a cool iron and steam to see how it reacts. It might stretch out completely and lose all its shape so it is better to find this out now before you try pressing seams or pleats.

Stretch out each cut edge to see if the fabric will “run” like your pantyhose.  Usually, only one edge will run. If your fabric has this characteristic you must use the pattern layout designed for a “napped fabric” with the hems toward the end that does run as neck-lines and waist-lines get the most abuse when worn and are most likely to start to run.

Most patterns are designed with a “straight of grain” indicated on each piece, however, patterns for stretch fabrics will often indicate “stretch” instead.  For these you will need to determine where on your fabric the greatest stretch can be obtained – across the grain or with the grain.  It is important to have the grain straight on any fabric before laying out your pattern and this is true with knits as well. Put  about  one meter of the selvages together and hold them above your head so you can see how the fold falls, shift the layers until you can see it is straight and not pulling in one direction or the other.  Pin the selvages together so they stay where you want them. Knits tend to be slippery and shift when you aren’t looking.

To hold your pattern pieces in place while cutting I prefer to use pattern weights with only a few pins holding the grain line in place. For heavy knits like fleece, cut the pattern out first so that when you cut into the fabric the pattern isn’t pulled into it and torn. For fine knits I like to leave a bit of tissue around the cutting line to help stabilize the fabric while I’m cutting. My preferred cutting tool is a wheel. It allows for more accurate cutting and prevents the fabric being pulled out of shape when lifted into scissors.

Marking knits can be done with tracing carbon and a toothed tracing wheel, although for the fine georgettes you may want to do tailor’s tacks.

My next blog will go into actually sewing on the knits.

Please feel free to contact me if you have any questions or comments.