The term fabric grain refers to the way threads are arranged in a piece of fabric. Grain is one of those quilting topics that you might not think is important, but the way we cut fabric in relation to its grain can produce quilt blocks that are accurate and easy to assemble — or blocks that just won't do what you want them to do.
Get familiar with some of the terms you'll see when you read quilt patterns and quiltmaking tutorials:
- Fabric's Warp Threads: 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 the yardage.
- Weft Threads: More threads, called weft threads, are woven back and forth, perpendicular to the warp threads and along the entire length of the warp threads. Weft threads make up the fabric's crosswise grain.
- Straight Grain Edges: The lengthwise grain and crosswise grain are both regarded as straight grain, sometimes called straight-of-grain.
- Fabric Bias: True bias is defined as the direction at a 45-degree angle to the straight grains. Quilters refer to any cut that doesn't run along a straight grain as a bias cut.
Stretch Differences in Fabric Cuts
Fabrics that are cut with edges parallel to either the crosswise or lengthwise straight grain are less likely to stretch out of shape than pieces with edges cut along the stretchy bias. The interwoven straight grain threads provide extra support.
Cuts along the (warp) lengthwise grain are less stretchy than (weft) crosswise grain 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 more warp threads per square inch than there are weft threads per square inch. The extra density adds strength.
Advantages of Straight Grain Cuts of Fabric
- Fabric squares and rectangles are nearly always cut with their edges along the straight grains to minimize stretch during sewing and handling.
- Since they do not stretch easily, long strips of fabric cut on the lengthwise grain make good quilt borders and sashing. They can stabilize and help you square-up the outer edges of blocks or quilt tops.
- Sashing strips with long edges cut along the lengthwise grain add stability to blocks.
- Long strips of fabric cut from selvage to selvage, along the crosswise grain of the fabric, have many uses in quilting. Two popular examples: we use the strips for strip piecing and we use the long strips as a starting point to cut patchwork shapes for quilts.
Selvages are the bound edges that run along the outer edges of the lengthwise grain. They are formed when the weft threads turn to change direction as the weaving process travels down the warp.
Fabrics are very tightly woven for a half-inch or so from the selvages inward, keeping the edges stable while the fabric is on the bolt.
Using Fabrics with Bias Edges
There are no threads to stabilize fabric along the bias, so cuts with edges that run along the bias are quite stretchy.
When Bias Edges Are Helpful
- Long, stretchy strips cut along the bias are easy to wind around the curved edges of a quilt when adding the binding.
- Thin tubes made from bias cut strips can be used to create delicate shapes for applique.
- Bias cuts can often be turned under easier for some curved and slanted applique shapes, including hearts.
When Bias Edges Create Problems
- Bias edges placed along the outer edges of quilt blocks or other patchwork components can stretch out of shape as you handle the quilt during construction, making it difficult to match and sew pieces together accurately.
- Triangles always have at least one bias edge. Analyze the pattern to determine the best placement for it -- usually on a block's interior and sewn to a straight grain piece when possible for stabilization.
Quick piecing techniques make it possible to eliminate handling bias edges when creating angled patchwork. Three examples are:
- Half square triangles sewn by pairing two fabrics
- Half square triangles sewn on a grid
- Quarter-square triangle units
- No-waste flying geese
There will be times when you decide to cut a patch with bias edges in the "wrong" position in order to use a specific part of a print or to make it flow with its neighbors. The cat fabric in the photo is one example of fussy cutting that resulted in outer edges that are slightly off the straight grains.
Occasional wayward patches are fine, but remember where the stretchy bias edges are and handle them with care.
Do a Stretch Test to See How Fabric Grain Differs
Becoming accustomed to the differences in fabric stretch will help you identify lengthwise and crosswise grain in scrap patches with no selvages:
- Cut a small square of cotton fabric with edges parallel to the straight grains.
- Tug on the fabric side to side, along one straight grain, then tug from the other direction.
- 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.
Experiment with fabric grain. It won't be long until you understand the best ways to place grain in your quilts to achieve the results you're looking for.