What’s Fabric Stretch Test and how to choose the appropriate knit fabric for your sewing project

Regardless of composition, fabric manufacturing typically falls into two categories: knit or woven. 

Knit or knitted fabric is a textile that results from interlocking yarn forming a series of loops to produce a particularly stretchy and flexible fabric commonly used to make various items such as t-shirts, sportswear, sweatshirts, leggings, sweaters, socks, and swimwear. It's ideal for snug-fitting apparel that doesn't require zippers and is much more challenging to sew than woven ones. 

Here are the most commonly used types of knit fabric: Jersey knit, Rib knit, Ponte, French terry, Interlock, Scuba or Double knit, Velour knit, Tricot knit, etc.

The knit fabrics may have different elasticity rates due to the mixed fiber composition and yarn interlocking, and a pattern maker will consider this when drafting a sewing pattern for a knit garment. For example, you may have a 100% cotton jersey knit and a 92% cotton jersey knit with 8% Elastane (Spandex or Lycra) - it's important to note that if the sewing pattern was drafted based on the characteristics of the second one, using the first one could cause fitting issues. So it's best to use a fabric that matches as much as possible the one used by the pattern maker. Therefore, to ensure optimal results, each of my sewing patterns using a knit fabric has a Fabric Stretch Test in its sewing instructions. 

This test is particularly helpful when you need to know whether your knit fabric contains Elastane (Spandex or Lycra).

You will find a page in the sewing instructions that looks similar to the one in the photos above. Print it at 100% scale and test a square of 10x10cm of your fabric:

1. Place the cutout inside the square on the page.
2. Hold the left side of the cutout with the left hand, as shown in the second picture.
3. With the other hand, stretch its right side in the crosswise direction (perpendicular to the selvage), until you feel it cannot be stretched anymore. 
4. The smaller squares on the upper side will help you determine your fabric's elasticity degree - 1V, 2V, 3V, and so on. If it stretches to 4V, it likely contains a good percentage of Elastane, typically over 10%.
5. Repeat the test lengthwise if the sewing project requires it, as this kind of fabric can stretch both ways, though it is only relevant when choosing fabric mainly for leggings, swimwear, and underwear.

You can also perform the test without cutting out your fabric and printing the test page. You can use a metric ruler just like the Test Page since each square on the page measures 1 cm. Here's how: 

1. With the ruler parallel to the selvage, hold your fabric with the left hand on zero.
2. With the other hand, pinch the fabric at 10 cm. 
3. Starting at 10 cm, gradually stretch the fabric until you feel it cannot go further. So, for example, if it extends to 14 cm, its elasticity degree is 4V (11 cm is 1V, 12 cm is 2V, 13 cm is 3V, and so on). 

It's important to note that this Fabric Stretch Test is specific to my sewing patterns. And it's worth acknowledging that other pattern drafters may have different approaches and procedures.

Last but not least, sewing knits initially may look challenging. But if you take time to test and explore other technics or maybe get to know other features of your sewing machine, the result might be surprising. Consistent practice is essential for achieving excellent outcomes. And the following two crucial main points should be kept in mind when starting to sew such fabrics: 

• Use a ballpoint needle for your machines. Note that brands offer different ballpoint needles for knit fabrics with Elastane and without.
• Use stretch stitches. Whether you are using a regular sewing machine or a serger/overlock machine, you have to set the stitch to be stretchy.

In my opinion, the above are the most important elements to consider when starting sewing knit garments. You can also find more details in the step-by-step instructions I provide for each sewing pattern.