January 26, 2007

Grading Stack Points


I am going to try and get back to my grading explanations today. My head is a bit fuzzy after a long week and an especially late night. To review, just click on the grading category link to the right. Click on the picture for a bigger view.

The diagram on the left shows three possible grading examples. This is a basic front bodice pattern piece that is folded in half. Each example is called a nest meaning each size is stacked on top of each other from smallest to largest. The stars represent the point of origin for each grade. The numbers at each point correspond to a grade rule. I will briefly explain each of these items below.

By laying your graded patterns on top of each other in a nest, you can easily see if your pattern is grading proportionally. The stars not only show the point of origin, but the stack point. You can stack your patterns in three general areas and have the grade look different each time. In computerized grading, you can move your stack point anywhere you choose and the grading software will update your grades automatically. For consistency's sake, it is important to determine before you start grading where your stack point/grading point of origin will be. Your actual grading will depend on it. This is also a critical first step in the actual grading process.

Each stack point will cause your grading to look different. Most of the grading world uses Example 1. The point of origin is placed in the center of the pattern pieces and growth occurs in all directions. In Example 2, the stack point is placed at the center front waistline and growth occurs to the side and upwards to the neck. Example 3 is the same result as 2, but placed at the center front neck.

I prefer Example 3 and all of my patterns are generally graded this way. It makes the most sense to me and the grade rules are simpler. Most of the proportional changes between sizes occur this way in nature. A person's neck doesn't actually move upward in each size, but rather their waist moves down. Perhaps this is just how my mind works. In any event, you can choose which ever point makes the most sense to you.

I have been using the term grade rules rather loosely in my previous grading articles. Grade rules refer to measurement charts broken down into grade steps. Grade rules can also refer to the actual change that occurs at a point. In the drawings above, I have numbers assigned to each point. Those numbers can refer to a grade rule. For example:

Rule X,Y changes
  1. 0, 0
  2. 1/8, 1/8


You can create a chart like the one above, if you prefer. This method is used in computerized grading and each grade rule is placed in a grade library (specific to a size range). Once a style is ready to grade, you simply apply a rule to each point and the pattern pieces will stay graded regardless of pattern changes. It is less helpful when hand grading and may make things more complicated. To be honest, I rarely use grade libraries when computer grading. They can speed things up if you have consistently similar styles. However, things always need tweaking, so I prefer to manually manipulate the grade at each point. Most grading software will allow you to assign a grade rule from a library and still manually edit the point. The computer will begin a grade command by starting with rule #1 and working around through each point. Rule 1 is almost always set as (0,0) and it should always be your stack point.

When hand grading, you should start your grading at your stack point. Once that is set, you then move to the next point, say the neck-shoulder point and mark all of the changes there. Work counter-clockwise (or vice versa, if you choose), around to each point. Setting up a consistent method will help you keep things straight.

Ok. Enough explanation. Decide on your stack point and get ready to grade.

3 comments:

  1. amanda12:40 PM

    I have what is probably a stupid question.
    Do you do the grading before or after you add the Seam Allowance to the sloper? Part of my brain says before because you are likely to get a better line, the other says after as it would be easier. I am loving your blog, thank you so very much.

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  2. does the above mentioned book have instructions on how to grade womenswear bodice and torso blocks with both front and shoulder darts?i bought a book called pattern grading for womenswear by gerry cooklin which was a complete waste of money.could you also tell me if zamkoff is better in that repsect

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  3. Zamkoff's book (I have the 1985 edition) does show how to grade a back bodice with a shoulder dart. The front bodice shoulder dart would grade similarly, if not the same. Handford does not demonstrate it. Still, no grading manual will illustrate every possible design variation. It is up to the grader to apply the principles to their own work.

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