How to create grade rules 1
This is the first portion of the theory part on how to create grade rules (grade rules are used to size clothing). Also see antecedent entries here, here and here if you have no idea what I’m talking about.
In spite of whatever you might read here, the practice and application of grading is easy. Honest. It’s much easier than pattern making. It’s also much less expensive. Please don’t let my theorizing lead you to believe it should be costly.
To make the other clothing sizes, one doesn’t increase height or girth willy-nilly. One does not make note of increased girths and apply those as grade rules as-is. It’d be easier if it were that simple. Unfortunately, an increase in girth can necessitate the addition of length, even if the figure is not getting taller.
As a size increases in girth, it also increases in length, even if the figure does not gain stature. The reason is, as a figure augments, the increased corpulence lengthens the distance the tape (or cloth) must travel to arrive at a given point. Meaning, that if you have two bodies of the same exact height measures (as defined in yesterday’s entry) but of varying weights, the tape-on measure will differ. In summary, just because an absolute height measure is listed as X, doesn’t mean that is sufficient to cover the distance on the body. Height measures (nor cervicale measures) are taken tape-on. But if you’ve read the measuring instructions included with the sample data set (CS151-150 pdf), you already know that. Good show.
Size augmentation is proportional; grading is not morphing. I don’t care to enter into any vigorous debates but the adult human form can be roughly segmented into eight lengths. Therefore, if a body increases in height by an inch, you can’t throw that inch in just anywhere. It has to be broken up evenly, over the length of the figure. Interestingly enough, the imperial inch measure, broken into eighths as it is, is ideal for grading; it’s almost a cheat sheet for sizing the human body. Leaving the discussion for another day, I don’t think it’s a coincidence.
Roughly, there are points to which eighths correspond, providing hints as to where you must apply your length grade rules as a proportion of total body height. The guidelines for adults are below:
Cervicale to back waist =1/4 (2/8)
Pubic arch height = 1/2 (4/8)
Knee height =1/4 (2/8)
So, if your prototypical size is increasing an inch in height (for the purposes of this discussion, girth related length additions are omitted), the center back length of a bodice would increase by a quarter. If it were a hip length top, it’d need yet another eighth making for a total of 3/8″. Likewise, you must be mindful where those measures are added. You can’t throw it all in one place. The distance from cervicale to the bottom of the armscye would be a third of the 3/8 (1/8); the armscye to the back waist is another 1/8 and you’d lengthen the hip length hem with the remaining 1/8″.
For slacks, length from the floor to the knee would be a quarter, to nigh hip is another quarter and then up to the waist another eighth, making for a total of 5/8″. Roughly. No one claims this is a precise science, bodies vary too much. However, you’ll find more bodies meeting this rough approximation than ones meeting any other mensuration description. For this reason, the application of grading is based upon this.
Using the charts as reference, the first step is to analyze the grade rules (see yesterday’s entry) with respect to the sort of garment one wishes to grade. If one is grading pants, then obviously one needn’t concern themselves with chest lengths and girths and the reverse is true as well.
The next entries will show how to organize data from the charts to specify your grade rules.