Understanding Fabric Grain

Have you ever watched a weaver making fabrics at a loom, moving threads back and forth to form the fabric? Our quilting cottons are made in a similar way, but using automation and on a much larger scale.

Warp Threads, the Lengthwise Grain

Long threads, called warp threads, are stretched on the loom and secured. They become the fabric's lengthwise grain, the threads that are continuous along the length of your yardage.

Weft Threads, the Crosswise Grain

More threads, called weft threads, are woven back and forth, perpendicular to the warp threads and along their entire length. These weft threads make up the fabric's crosswise grain.

Selvages

Selvages are the bound edges that run along each long side of the fabric. They are formed as the weft threads turn to change direction as the weaving process travels down the length of the warp.

Straight Grain

Pieces with edges cut parallel to either straight grain--the lengthwise or the crosswise--are less likely to stretch out of shape than pieces with edges cut along the bias, because the interwoven threads give their cut edges extra support. Cuts along grain lines are referred to as straight grain cuts, or straight of grain cuts.

Cuts along the lengthwise grain are somewhat less stretchy than crosswise cuts:

• Unlike the moving weft threads, the warp threads were firmly attached to the loom during the weaving process, holding them in place and enhancing their structure.
  
  
• The interlaced weft threads help stabilize the warp threads.
  
  
• There are usually more warp threads per square inch than there are weft threads. The extra density adds strength.

Fabric Bias

True bias is defined as the direction at a 45-degree angle to the straight grains, but in quilting we refer to any cut that doesn't run along a straight grain as a bias cut. There are no threads to stabilize fabric along the bias, so cuts with their edges along the bias are quite stretchy.

Do a Fabric Stretch Test

1. Cut a small square of cotton fabric with edges parallel to the straight grains.
   
   
2. Tug on the fabric side to side, along one straight grain, then tug from the other direction. Do you feel and see a difference? Did you notice slightly less stretch in one direction? That was the lengthwise grain.
   
   
3. Now tug on the square from corner to corner--along the bias. It probably stretched quite a bit, and if you tugged too hard it may have become permanently distorted.

Becoming accustomed to stretch differences helps you identify lengthwise and crosswise grain in scrap patches with no selvages, like those small squares scrapquilters love to swap!

Putting Fabric Grain to Work for You

• Fabric squares and rectangles are nearly always cut with their edges along the straight grains to minimize stretch during sewing and handling.
  
  
• Because they do not stretch easily, lengthwise grain strips make good quilt borders and sashing. They can stabilize and help you square-up the outer edges of blocks or quilt tops.
  
  
• Triangles always have at least one bias edge. Analyze the pattern to determine the best placement for it--usually on a block's interior (rather than ending up around its outside edge) and sewn to a straight grain piece when possible for stabilization.
  
  
• Using stretchy bias strips makes it easy to apply binding to a quilt with curved edges.
  
  
• Bias cuts can be turned under easier for some appliqué shapes, like hearts.

Experiment with fabric grain. It won't take long until you understand the best ways to place grain in your quilts in order to achieve the results you're looking for.

Read more about fabric grain and find hundreds of quilting patterns at my About.com Quilting Web site.

©Janet Wickell, 2000 & 2005 & 2012