A Little Bit (OK, A LOT!) About Single Jersey

Single jersey is the most common knit fabric, and it’s used in many garments from the classic cotton T-shirt, to slinky knit tops or dresses. As it is the recommended fabric for both the Galaxy T-shirt and the Isosceles T-shirt sewing patterns, I thought thought I would go over a few interesting things that might help you with your choice of fabric.

First of all, single jersey is a knit structure, and is knitted in various yarns, made from different fibres like cotton, viscose, wool, etc. The resulting fabric is correctly referred to as “whatever the fibre content is” single jersey, eg 100% cotton single jersey, cotton elastane single jersey, merino single jersey, etc. This differentiates between the wide variety of single jersey fabrics that are possible.

You might see the fabric referred to simply as ‘jersey’, however that is not technically correct as there is such a thing as ‘double jersey’ which is quite different, so to avoid confusion it is best to use the term single jersey.

Knit structure

Distinguishing between the right and wrong side is easy when you know how, although for fine gauge knits you may need a magnifying glass! The first step is knowing a bit about the knit structure. If you can hand knit, you will already be familiar with single jersey knit structure:

A row of needles pulls yarn through the loops from the back to the front to create the next row of loops. Although either side can be used as a right side, there is a technical front or face side. Here the side arms of the loops appear as columns of V’s, giving a smooth appearance. On the technical back, the bottom of the loop and the top of the loop below intertwine to form a wavy ridge.

Grain

The columns of loops are known as wales, and each row of loops is called a course, similar to the warp and weft of a woven fabric. Wales usually correspond to the lengthwise grain and run vertically up and down the garment, while courses run horizontally across the garment.

Gauge

Gauge (gg) is the number of wales per inch, an indicator of the size of the stitches in the knit. A fine gauge knit has smaller stitches, eg 14gg equals 14 wales per inch. A coarse gauge knit has larger stitches and less wales per inch, eg 5gg equals 5 wales per inch.

The yarn density can considerably alter the fabric – a fine yarn on a coarse gauge will result in a loosely knitted fabric, and a thick yarn on a fine gauge will result in a dense fabric. Watch out for loosely knitted fabric when selecting your t-shirt knit – although a flimsy fabric is perfect for some designs, you probably require a fabric with some body for the Galaxy and Isosceles tees.

Spirality

Single jersey fabric can be knit on a flat bed machine which produces rectangles of fabric or it can be knit on a circular machine which knits around and around to produce a tube of fabric. The tube can be opened out and sold flat, or sold as a tube.

Circular knitting is fast, but it comes with a disadvantage – spirality. If you imagine hand knitting in the round, for each round the row spirals upwards by one course. Now imagine an industrial knitting machine with several feeders, for each round the rows spiral up by several courses. A high twist yarn exacerbates the effect, meaning the courses may not be perfectly perpendicular to the wales in the finished product. In a well designed fabric this may not be very noticeable, but some examples on the market are quite skewed! Horizontal stripes and mélange knits only accentuate the effect. Trying to correct the skew manually is a no win situation – so it is worth assessing whether the degree of spirality is acceptable to you before buying.

Curling

A characteristic of single jersey is that it is not balanced like a double jersey is, and the twist of the yarn creates a tendency for the fabric to curl. It curls towards the front at the top and bottom, and curls toward the back at the side edges. Although this can be a convenient indicator to which is the face side, it can be very inconvenient when it comes to sewing! The curl factor can vary considerably between fabrics, and this is worth assessing prior to purchase too.

Fibre content

The characteristics of single jersey fabric are also dependent on the fibres used to knit it. Factors such as weight, stretch, drape and stability all vary with the yarn content. Compare a classic t-shirt cotton to a slinky polyester jersey, or a cushiony wool/cashmere, and you will know what I mean!

I have recommended 100% cotton single jersey for the Galaxy and Isosceles to ensure you achieve a similar effect to the sewn samples. Viscose/rayon single jersey or linen blends will still work, but the effect will be slightly different – drape will be enhanced, and the neckband may require minor adjustment.

Weight

Weight of a fabric is measured in grams per square meter (gsm) or ounces per square yard. Weight is affected by the fibre content (some fibres are naturally heavier than others), and the yarn density (whether the fabric is loosely or densely knitted). Typical weights for medium weight cotton t-shirting are 140-160gsm (4-5oz), so if you choose a fabric in this range you should attain similar results to my samples.

Stretch Factor

Single jersey structure results in a fabric that has stretch in both length and width, although stretch in width is usually much higher. Most T-shirt knits stretch about 25-30%. This means a 10cm piece of fabric folded along the crossgrain (courses), will easily stretch to 12.5 or 13cm.

Recovery (the ability of a fabric to return to its original state) is another factor that you might like to assess in single jersey. It is not a critical factor for t-shirt styles, but you would require good recovery in a fabric intended for trackpants for instance.

Drape and Stability

The drape and stability of a knit is affected by fibre content of the yarn, the yarn density, and whether the yarn is smooth or textured. Compare a smooth, loosely knitted viscose, to a textured wool boucle, to envisage the difference these factors can make! Laddering can be a problem in loosely knitted fabrics and/or where the friction between yarns is low. This is where the loops in one or more wales unravel downwards and leave horizontal bars like a ladder. Because t-shirting is relatively stable, it is not a big problem.

As you can see, there are tons of variations possible in this one knit construction. Hopefully this summary gives you a few things to look out for when purchasing t-shirting for your Isosceles or Galaxy tees – or for any other knit fabric!