How can I straighten the grain of my fabric?
When a fabric is “on-grain,” the lengthwise and crosswise threads are at an exact right angle to each other. Woven fabrics always follow the grain because they are made with the actual warp and weft threads. With wovens, when the grain is off, so is the pattern. With printed fabrics, their designs are printed on top of the woven threads. So the grain can be off and the pattern can still look okay
You can check to see if your fabric is on-grain by establishing a straight line across, from selvage to selvage, then folding the fabric to see if it squares-up.
To do this, lay out your fabric panel right side up and flat on your work surface.
Near the top cut edge and starting at one side of the selvage, find one thread that goes all the way across (crossways). Start pulling it.
Ideally, you can simply pull the thread right out of the fabric. But if not, just pull until the fabric puckers along the thread, then keep bunching the fabric and pulling every few inches until the pucker reaches the opposite selvage.
Either way, pulling out this single thread will give you a straight line across the fabric.
The methods listed above still work without a selvage. It just makes it a bit harder to find the horizontal thread to pull. Place the fabric on your work surface oriented so the weft is running as it should: horizontal. If you’re not sure, make your best guess. At one corner, fray the fabric so you can get ahold of one thread and pull as described above. If your pieces are small, there may not be much you can do since the cuts from the larger fabric have already been made.
Using this thread line as your guide, cut all the way across the fabric.
Some folks prefer to rip across. To do this, snip about ½” in from the selvage, then rip the fabric across. Your ripped edge will need to be pressed flat.
Fold the fabric lengthwise so the selvages align and are perfectly flush. If the two sides of the edge you just cut also line up and are flush, your fabric is on-grain.
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