Anyone who sews, has heard the term ‘straight grain’ or ‘grainline’. So exactly what does that mean; is it important. And yes – it is absolutely important.
So what is the grain line? The grainline is the direction that fibers are woven in your fabric. You use the grainline to align your pattern pieces and cut your fabric, so it hangs nicely on your body, doesn’t lose shape or distort.
So what happens if you don’t cut on the grain line? If it’s off-grain, you’re cutting closer to the bias, which increases stretch. In drastic cases, if your pattern pieces are not cut on grain, your fabric really will stretch and grow as you wear it.
Fabric that has an obvious design like checks or stripes will be visually off balance.
There are three graininess for woven fabrics to understand.
The lengthwise grain: Your fabric has two finished edges, which are the selvages. On woven fabrics, the threads that run parallel to the selvages are called warp threads. This is your lengthwise or straight grain, the line you’ll most commonly use to orient your pattern pieces lines/arrows as you cut them out. When fabric is “on-grain” or you are supposed to cut “on the grainline,” this is the line you want to follow.
The crosswise grain: The threads that run from selvage to selvage are called weft threads. This is the crossgrain of your fabric. And guess what? It’s ok to cut fabric on the crossgrain! It might have a bit more mechanical stretch than the lengthwise grain, but you can play with stripes and plaids for fun.
The Bias Grain: The bias grain runs diagonally between the selvages. This is the stretchiest grain of your fabric. It is used to make bias tape so that it can stretch around curves. Some patterns will specify to cut on the bias because it gently wraps the body so well.
To illustrate these grainlines, we’ll use gingham fabric because these little checks will make it easy for you to see what’s happening.
You found the grainline. Now what?
Once you’ve found the grainline on your fabric, just match it to the grainline on your pattern piece—the line with the double-headed arrows. You can also use pattern pieces that have a straight edge in place of the double headed arrow line.
Ensure that the pattern piece’s grainline marking is parallel to the grainline on the fabric. You can use your ruler on either end of the arrow to make sure it’s straight.
To ensure you are on the grain line – measure the distance at the top and bottom of the double arrow line to the selvage edge. You want the measurement to be the same.
What about knit fabrics?
Now knits are a bit of a different animal.
Knits don’t technically have a grainline in the same way that woven fabrics do. That’s because the fibers are not woven together, they’re knit together. However, we still refer to knits as being on-grain or off-grain.
You can tell if your knit is straight by looking closely at a cotton jersey. There’s tiny little ribs—like the wales on corduroy—that run parallel to the selvages. That’s your straight grain on a knit.
But here’s the tricky part; knits have a direction of the greatest stretch.
Often knits have the most stretch on the crossgrain, so you can line up your pattern pieces on the grainline, and then the fabric will stretch around your body.
However, sometimes the fabric plays a trick on you, and it has more stretch on the actual grainline, also called vertical stretch. This means the fabric stretches the most up and down, so you want to orient that direction of greatest stretch according to your pattern’s instructions.