In order to achieve a perfectly constructed garment, it is important take a few fabric preparation steps before aligning and cutting your sewing patterns. Perhaps the most important of these preliminary steps is realigning fabric grain.
If your garment pieces are not cut on grain, you may find that the final garment does not feel and lay properly, often pulling the fabric askew. The most common example of off-grain issues occurs with denim fabric when the pant leg seams are not sitting straight but rather pulling to one side at the bottom.
While off-grain risk is lower with some fabrics and much higher with others, it is good practice to realign the grain of all non-stretch woven fabrics prior to cutting the garment components. Not only will this provide a more enjoyable working process, it will also ensure that the final garment feels and fits comfortably.
You can tell that a fabric is off grain when the intersecting threads are not perfectly perpendicular. In addition, the fabric corners may be pulling to one side even if the fabric's crosswise edges have been perfectly straightened and cut on grain.
Fabric can go off-grain either at the manufacturing level or due to the way it was stored for an extended period of time. Luckily, fabric grain is not difficult to re-align. A simple technique is used across the board for all woven fabrics:
Start by spraying the fabric with water lightly to soften the fibers. Some stretching and pulling is required in the re-alignment process and moisture will give the fabric some much needed flexibility.
To straighten the grain, pull the fabric diagonally along the bias, from selvage to crosswise edge. Start at one corner and continue stretching and pulling across the bias until you can visually see the grain fully aligned. When aligned, the fabric threads should intersect at straight angles and the fabric corners should not be pulling the fabric askew.