This post is in response to all the questions we have been getting regarding the Bias Skirt Fabric Calculator we published a few months ago. It seems people find this document to be a very useful tool but I need to fill in the blanks a bit more with some foundation theory. As I was writing this post it quickly dawned upon me that there was way too much data to put into one post so I will be breaking them down into several posts. The primary focus of these posts are for sunburst pleating. However, much of the theory can be applied to non pleated skirts as well. Also, note that when I say “skirts” I am referring to skirts that are attached to a dress as well as a separate skirt with a waistband. It’s important to understand the geometry of circles because they come up a lot in designing and dressmaking. I won’t list them all now but ruffles are the most basic use of circles. We can address those later!
A bias skirt can be made from a half a circle, a whole circle or from several circles shirred together. Usually bais skirts are made from one complete circle (2 half circles). Depending on the fabric, half circle skirts have more of an a-line look so most people would just cut an a-line skirt on the straight grain instead of a half circle bias skirt. Please keep in mind that is my personal observation and not any kind of industry rule. Dealing with bias can be tricky…most novice sewers find it easier to sew and hem skirts that are not bias because of skill level or the need for specialized machinery. In addition, most large scale manufactures prefer to cut on the straight grain for several reasons: they lose less fabric, there are a limited number of factories that understand bias, and the ones that do charge more to produce garments. Actually, you would be surprised to see some factory workers who have sewn clothes for years and don’t understand a thing about garment construction. They just know one operation on one particular machine. Maybe I should save the issues regarding production for another post. I’m going off on a tangent again.
Ok… so putting several circles in a skirt is something that is common with couture designers. Whether it is pleated or not the fullness in the skirt is beautiful. This is particularly evident in dancers when they whirl around and grab their skirts. If they only had one circle in the skirt it would not look as dramatic.
Below is technical drawing for a half circle. Notice the grain lines in the half circle, especially where it is on the bias. These are the areas where the fabric stretches due to gravity when hanging. These diagrams may be boring but trust me these principles are very important when you want to contour a 2 dimensional fabric onto a 3 dimensional body.
Below we have two more of the half circle diagrams. However, they show two different ways of cutting the skirt. The first diagram shown is for a CB (center back) zipper. This configuration is usually for a dress. The second drawing below shows another layout for a side zipper. Notice where the bias of the skirt would fall on the body. In the top drawing we have the bias on the sides of the body and for the bottom the bias is on the CF (center front) and CB. Theoretically speaking there is no real advantage between the two with the information we have now. However, that could change depending on the fabric. That is something that becomes apparent in garment construction after years of experience. Many things can change depending on the fabric.
The drawings below are directly out of our Bias Skirt Fabric Calculator. Again they explain the grain lines and the layout for cutting full circle bias skirts. The document we created is very useful for calculating the amount of fabric required to cut a skirt. A very practical tool to have in your iPhone when you are in the market. We save a tremendous amount of money with this document now since we purchase so much silk…and we all know how expensive silk has become these days!
The image below would be ideal for a side zipper skirt.
The image below shows the layout if you are cutting a full circle skirt with a CB zipper. The advantage to this layout is a small saving in fabric since there is less fabric wasted. However, the extra seam does add more time to your project. The decision is up to the designer. Some dresses or gowns have side zippers so either way can be used.
As I mentioned previously, circles are used a lot in dress making. Below is a couple of pleated bias dresses we have made in the past using full pleated bias skirts.
Stay tuned….a lot more to come 🙂