Cutting your fabric before straightening the grain will result in a garment that may hang or twist in an odd way. It is important to correct this before cutting.
To make sure that the lengthwise and crosswise threads are at right angles, and that the fabric is “on-grain,” it’s necessary to straighten one of the cut ends. If there is a prominent design line, such as a woven stripe or plaid, cut along the design. Double gauzes are woven with tiny “tie-downs” between the two layers of fabric. On the reverse side you should see a series of small dots in a grid pattern – use these dots as your guide to correct the grain.
Do not use a printed line as a reference; the print may not match up with the grain. If there is not a design line to follow, you need to pull a crosswise thread.
Snip through the selvedge, find one crosswise thread and pull it, like a gathering thread, until you reach the opposite selvedge. If the fabric is loosely woven, you might be able to pull the thread completely out of the fabric. If it is tightly woven, you will need to pull the threads every few inches or pull it slightly so it puckers; then slide the thread and push the fabric repeatedly until you reach the opposite selvedge. Cut the fabric along the pulled thread.
After you’ve achieved an “on grain” edge, pull the fabric on the bias in the direction that it needs to be straightened. Match the selvedges and pull gently until the fabric cut edge is perpendicular to the selvedges. Mist or steam press to “fix” the fabric.
You can’t pull a thread on a knit fabric, and you can’t steam or pull it to straighten the grain. Many knit fabrics appear permanently slanted; this is known as “torque.” The best way to use these fabrics is by hanging the fabric vertically and allowing it to drape as it will.
Use the naturally folded edge as your “straight of grain” line. With extreme torque, you may have to compensate by modifying your pattern layout.
If you have a knitted in stripe you can use this as your straight of grain guideline.