Monday, May 28, 2012

Pattern Drafting and Grading

I've recently noticed while reading comments in the Ravelry designer forums that there is a melding of the terms drafting and grading. This probably has been happening for some time but because my definition is two separate processes I think I have misunderstood many of the comments and questions posted.

When a pattern is drafted it is an original plan that is used to create a garment. It has a specific size wearer intended as it's target. It is usually based on a medium size if the end result required is multiple sizes, or it is a customized pattern for a specific individual.

Grading refers to the process of proportionally increasing or decreasing the size of a pattern, while maintaining it's shape, fit, and scale of the details. An example would be making a collar or pocket size stay in proportion to a larger or smaller garment. It also means that seams, darts and shaping are in the same place on the body in all sizes. The garment you knit will look the same as the one in the pattern photo even though that was taken on a model of a different size than you. 

The change of size assumes that the type of body is still within a specific target range, for example what retail refers to as a Misses size. Plus, Junior, Petite and Tall size grading starts with a different original pattern due to the differences in proportion that those categories target. For example, Misses sizes have a eight to ten inch difference between the waist and hip measurement and Junior sizes target a less well defined waistline.

In the mainstream fashion world the process of pattern making and grading are often done by different people. Pattern making is the translation of the design idea onto a paper template. Grading deals only with size issues. Some designers outsource the grading of the original pattern to companies that provide this service.

In manufacturing there are several methods of grading: cut and spread and computer grading are the common methods. 

Grading only makes a garment section larger or smaller and isn't intended to change the fit. Grading also reinterprets the pattern with the understanding that people of different sizes are proportionately different. It takes into account that different body parts change at different rates and proportional amounts. The amounts are based on established measurements but there is no one common system used by garment makers. They are also based on heights that do not vary more than four inches in total height.

Take a look at the drawing I've included at the top of this post. You will notice that there are three sizes on the one piece but the increments are not even as you follow the lines around the neckline, across the shoulder and down the armhole seam and side seam. Look at the edge of the shoulder and at the bottom of the armhole and you will see that in those spots the sizes match up. Knitting patterns use a single schematic to represent all sizes. These details are not reflected, so some of the differences between sizes are not obvious to knitters.

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