One concept that many of my students have questions about is “grainline”. No wonder! Like lots of things in life, there is a relatively straightforward answer that provides 88.5763% of the needed information, but there are many little nuances that are often ignored or not dealt with.
What I tell students is that for woven fabrics, the lengthwise grain (called warp threads, tho I often forget this detail) is ALWAYS parallel to the selvedge edge of the fabric, and the crosswise grain is ALWAYS perpendicular to the selvedge edge. Usually the next question is “What’s the selvedge?”. OK – that is the tightly woven edging that runs the length of the fabric, sometimes a different color, sometimes with fuzzy loose threads on the outside edge, and is always perpendicular to the cut edge of the fabric. The selvedge is what attaches or holds the fabric to the loom during the weaving process.
Well, all of the above is true. But it is not really complete. It is basic information intended to start introducing a complex concept to beginning students. Because there is also a bias grain, which is any angle on the fabric other than parallel or perpendicular to the selvedge. And true bias is exactly 45 degrees to the lengthwise grain. Of course, we haven’t even started talking about knits. Knits are made up of knitted loops, not lengthwise (warp) and crosswise (weft) threads. The vertical loops are called ribs and the crosswise loops are called courses.
Are you confused yet? I looked in many of my reference books, as well as online, and IMHO the Threads SewBasic : Grainline article is both comprehensive and understandable. Download the PDF file and see if it helps your understanding of grainline. The main thing to keep in mind with grainline (from my perspective) is, why is it important? The reason is because it determines how the finished garment falls on your body, and whether it will maintain it’s original shape over time. The “grainline police” will not pay you a visit if you cut a pattern piece “off grain”. And maybe it will not even be noticeable in the final garment. Maybe. 🙂