Grainline, selvedges, warp, weft and bias - some fabric basics
Updated: Aug 26
When sewing clothes using dressmaking patterns, you will come across the word 'grainline'. The grainline is a line or arrow printed on each pattern piece to indicate the direction of the fabric grain.
Aligning the pattern pieces correctly on the fabric matters because fabric behaves differently when pulled along the different grain directions:
the lengthwise grain is the most stable
the crosswise grain is slightly flexible and
the bias is the most stretchy.
If pattern pieces are not correctly aligned, the finished garment may warp, twist or show unwanted creases.
When you are ready to cut the pattern pieces out of your fabric, line up and pin each pattern piece onto the fabric with the grainline arrow parallel to the fabric’s lengthwise grain.
But how do you know where the lengthwise grain is on the fabric?
To work out in which direction the fabric’s lengthwise grain runs, it is useful to understand how fabric is constructed. Fabric that is woven on a loom has two sets of threads that run perpendicular to one another.
The vertical threads are fixed to the loom and are called ‘warp’ threads - they make up the lengthwise grain.
The threads that are woven over and under those warp threads horizontally are called ‘weft’ - they make up the crosswise grain.
It's so easy to forget which one is which - warp or weft - so my mnemonic for this is to say:
"right to left creates the weft"
You may wonder how you can tell which of the fabric's threads were once attached to the loom if you are looking at a strip of fabric. This is where selvedges come in, because the lengthwise grain of a fabric always runs parallel to the selvedges.
Selvedges are created when the weft thread loops around the warp thread at the left or right edge of the fabric every time a row of weaving is completed. This creates an edge that cannot unravel (a 'self-edge'). Note that machine made fabrics sometimes still have a fuzzy edge at the selvedges, but there is a distinct strip of very tightly woven fabric that keeps it from unravelling. The selvedge is also the part of the fabric that any of the manufacturers' details such as the fabric's name or number (selvedge ID) are printed on.
What if the selvedges have been cut off?
If you have a piece of fabric where the selvedges have been cut off, you have the following options to identify the lengthwise grain:
Pull the fabric horizontally and vertically - the warp threads are tighter than the weft threads, so you will feel less ‘give’ when pulling along the lengthwise grainline.
Rip the fabric (if you have enough) - tearing fabric along the crosswise grain is much easier than ripping along the lengthwise grain. If you struggle to rip the fabric, you know it's the lengthwise grain.
Where is the bias?
Some dress patterns require you to cut a piece of fabric 'on the bias', for example dresses and skirts that stretch or drape over the body, or when making 'bias tape'. The bias of a fabric is the 45 degree diagonal between the weft and the warp, where the fabric gives maximum stretch and flexibility.
