I hope you are all sitting comfortably today, and are ready to concentrate as I think I may be about to confuse us all!!
I am going to attempt to explain grainlines after being taught about them in my Pattern Cutting class a few weeks ago. I honestly do think I understand them in practice, but trying to explain them to you in an easy to understand way might be a bit beyond me (those that are far more knowledgeable on such matters feel free to point out any errors). Here goes though!
I drew a little diagram in a past post, which shows the main things to understand about the construction of fabric. Here is a more professional one as a reminder:
On a pattern the grainline is shown by a straight line with an arrow at each end. Here they are the lengthwise grain, the crosswise grain and the bias grain.
These straight lines should always be parallel to the selvedge edge when laying out pattern pieces. This is done by using a ruler to ensure each end of the grainline is the same distance from the selvedge / selvage.
I am going to tackle each of the grainlines individually to try and explain them a bit more in regards to skirts. Essentially, the grainline that is used affects the way that the skirt will hang.
Lengthwise / Straight grain
This image shows the front of a skirt. It is cut using the straight grain through the centre front / middle. The lines indicate this grainline, and the red line with arrows shows what would appear on your pattern.
By cutting the fabric this way, along the warp, the skirt will hang straight and the sides will go out.
The bias grain is 45 degrees to the original grainline. It means the fabric will hang in a softer way, and pull to the body. This grainline has the most stretch and give.
You can also achieve interesting results using the bias grain on patterned fabrics. Imagine this was a checked or striped fabric on the front of a skirt.
The final grainline we were taught about was the gore grain. This grainline can be used if the skirt is made of four pieces, and the grainline is put through the middle of the leg.
It was a popular grainline in the 1940s as it didn’t waste as much fabric as using the bias grain, but was much more flattering than using the straight grain which can look a bit like a triangle!
It is created by marking the centre point between the centre front and side of the pattern piece, and the centre point on the hem. You then join these two points with a straight line and this is the gore grain.
You can also create a bias gore grainline which is 45 degrees to the gore grainline.
I found this diagram helpful in summing everything up.
Singer Sewing Book, 1969
Basic Pattern Skills for Fashion Design, Bernard Zamkoff and Jeanne Price