Grading is “a methodical and mathematical process that’a used to “grow” and “shrink” a style to fit a range of customer sizes….Grading is not morphing; it cannot change shape, but only makes an existing shape larger or smaller.
(Kathleen Fasabella, “The Entrepreneur’s Guide to Sewn Product Manufacturing”)
Incorrect pattern grading, whether the sizes are off or the shapes have changed between sizes, is one of my biggest complaints in the indie pdf market, and manually correcting grading is an irritating, time-consuming task when I want to use a cute new design. Since I can’t have inside-access as to how designers are doing their grading, I don’t know what causes the weird shape changes and off-chart measurements. I have a guess, which I’ve mentioned before (here and in some FB groups) but apparently my guess has been misunderstood so I thought I’d clarify it.
I’ve stated that “non-specific-to-patternmaking, all-purpose vector-based computer programs” such as Adobe Illustrator, when used for the purpose of grading patterns, are TYPICAL of incorrect grading. This was recently misunderstood as me saying that Illustrator was the FAULT. It’s not of course, it’s simply a tool for design. Patterns can be perfectly graded in Illustrator, or a total mess…just as they can be on paper. Grading is an art, and usually you are only required to take one term in design school, as an overview to help your future communication in the garment industry. Most grading education is done within the field, hands on. But you can certainly learn it on your own, with a good textbook or tutorial. The grading process is simply a series of steps, moving the base-size pattern piece up/over/down/over, according to a set of measurement grade-rules assigned to each corner, notch, and dart, to create a “nest” of sizes with consistent shapes:
If you analyze 3 different ways that patterns can be graded, you’ll see why “Illustrator-graded” patterns CAN BE more susceptible to grading errors. These 3 methods of grading are:
- Manually: paper and pencil, either by hand or by grading machine
- CAD (computer-aided design): Pattern-specific computer systems, including heavy-duty products such as Gerber, Optitex, Assyst, or smaller programs such as Wild Ginger, Tukatech, PAD
- Illustrator, or any similar all-purpose vector program
Manually: the “fitting size” pattern in oaktag (like a flexible cardboard) is placed down on a large sheet of pattern paper, and moved up-and-over, and down-and-over, while maintaining the grainline, according to the grade-rules: a set of measurements according to the size grade. The pieces can be moved by hand or by machine. At each move, points are plotted at each of the pattern corners, and then afterwards the lines are connected using a straight-edge, hip-curve, or a French curve. If done accurately, shapes will be automatically maintained throughout the size range, corners will still be trued as the fitting-size pattern pieces were, and measurements will automatically give the correct ease for each size. Also, a pattern drafted and graded by hand and then scanned into Illustrator can be very accurate.
(Photo from “Grading Techniques for Modern Design” by Price and Zamkoff…my textbook from F.I.T.)
CAD Pattern-specific grading system: The computer program automatically does the shifting up-and-over, and down-and-over, according to the grade-rules set by the operator. Shapes are automatically maintained, sizes are automatically measured. Note: just using a CAD pattern-grading system doesn’t guarantee success. I’ve bought many Big Four patterns where the size grading was way off from the measurement charts given. You still have to understand the numbers of grading, and how much of a grade you want between the sizes in the body-size-chart you have set up for your garment line. You still need to understand garment ease, and know that ease is not static between sizes: it grows as the body girth increases. But a CAD (computer-aided-design) system dedicated to patternmaking WILL maintain grainlines for you, will keep consistency between shapes and lines for you, will greatly simplify your work. However, depending on the features of the system, you’ll pay for that professional outcome. Some of these systems are a wildly expensive investment, even on a lease basis. Many small businesses send out their patterns to be graded, to services who own one of these systems….or else choose to purchase a programs with fewer “bells and whistles”.
Illustrator or all-purpose vector program: this is an in-between process, one that is used by many indie businesses. This type of program isn’t designed for garment patternmaking, although it can be adapted for that use. It’s affordable, and can create a clean and professional-looking product. Customers who purchase a pdf-file sewing pattern these days expect a digitized product: hand-drafted patterns are looked down upon by many (not by me…I’d far prefer a correctly drafted/graded penciled pattern than an incorrectly digitized one!). However, a digitized pdf using a limited-ability all-purpose program can, sometimes, mask poor grading. And that’s where my criticism lies.
If a designer has learned to grade manually, or has used a CAD system at work in industry, chances are that when she uses Illustrator, she will use the same methods of grading. But if a designer isn’t proficient in grading, possibly she will use Illustrator to plot the points for each size, not using the standard up-and-over, down-and-over grade rules. This can lead to sizes and ease being inconsistent across the size range. For example, these side-seam lengths (left) and shoulder heights and widths (right) do not have consistent size increases. they were graded into 3 different “nests”. Many kids’ apparel manufacturers divide their full size range into 3 nests to more accurately fit the changing body shape of growing children :
- size 12 months gets fit-approved and is graded down to newborn and up to 24 months
- size 4 graded gets fit-approved and is graded down to toddler 2 and up to childs 6X
- size 8 graded gets fit -approved and is graded down to 7 and up to 14
This is great, however the jumps between the nests seem a bit off:
Then, when connecting the plotted points into curved shapes (armscye, sleevecap, neckline etc.) , instead of copying the original fitting-size pattern-piece curve, she may pull out vector curves for each size, and those curves can vary in shape (and not match a French curve at all). For example, these armscyes (left) and necklines (right) are inconsistent in shape between sizes:
THIS is when I say a pattern is “typical” of Illustrator drafting: the computer program is not at fault obviously, it is user-error in either not understanding the objective mathematics of grading, or having difficulty drafting the subjective shapes using the limitations of the program. Illustrator is NOT an easy program to use for pattern grading. It may be the only affordable choice available for digitizing, but it demands greater skill than using a pattern-specific program.
At this point I’m sure you wonder “Are there really RULES of grading? Isn’t it subjective? Can’t you grade any way you want to?” Well sure, it’s your product, you can do whatever you want to. Although the standards used in industry make it much easier to grade patterns, and ensure that shapes and measurements will be consistent, anybody is free to make up their own rules. But at least consider these two concepts:
- Objective grading is mathematical and asks “Does each garment size fit each body size, with appropriate ease as the body increases?” The grader sets the grade rules for the width and height increments.
- Subjective grading is visual and asks “Does each garment size appear the same in shape throughout the size range?” The grader must decide what the measurement rule is for each corner point, which determines how necklines, armscyes etc appear in shape going from size to size.
Obviously objective fit is more important that subjective appearance: you or your customer need to be able to wear the finished garment comfortably, and choose a size accurately. Whether it looks consistent between sizes, may be un-important if you are only sewing one size. For anyone sewing to sell, it is a valid concern. Your customer’s flower-girls in sizes 2 and 6 need to look like they’re wearing matching dresses. I’m going to compare 2 patterns to show how they were graded to different grade rules, using different software, to show you that it’s not the METHOD being used that makes the difference, it’s what the designer inputs. This is a bit tricky showing only parts of patterns so bear with me.
I’ll be comparing Rabbit Rabbit “Hummingbird and Bella Sunshine “Felicity”:
Both patterns have a single main fitted pattern piece (bodice front), an elasticized back, fabric straps, and a free-fitting skirt. It appears that Hummingbird (on the left) used an Illustrator-like program, because the shapes are just the tiniest bit off-kilter (I’ve tried Illustrator, it’s not easy to get consistent smooth curves!) but it’s nothing that would affect cutting out the pattern smoothly. It appears that Felicity (on the right) was graded in a pattern-specific CAD program:
Whether Hummingbird was graded manually and then scanned and digitized, or the median fitted size was scanned and then graded in Illustrator, I don’t know.
I cut out a size 4 in both patterns, and tried sliding then up-over-down-over to see if the grading was technically accurate. In both cases the points are spot-on; the grading on both is very professional:
Next I checked the graded fit of the bodice compared to the body measure chart given. Since the back is elasticized, I only checked the grading of the bodice from Center-Front to Side-Seam. Hummingbird (left photo, with side-seam to the left) has a grade rule of about 1/8″. Multiply that times 4 for left/right/front/back = 1/2″, which means the finished garment will get tighter as the sizes go up, since each body size grade is about 1″. Felicity (right photo, with side-seam to the right) has a bodice grade rule closer to 1/4″ (a bit more in the larger sizes) , which means that multiplied times 4, the garment will grow about 1″ per size, same as the body chart (with some extra ease in the larger sizes). Remember, the grade rule used for these points is not dictated by the program or method used for grading: it is up to the decision of the designer:
Then I measured the bodice pattern piece in every size as if I were Alpha-testing the patterns, and compared the results to the body size charts, to see if the correct amount of ease was graded in to the chest measure. For Hummingbird (left chart) , the amount of ease ranges from positive 1 3/4″ to negative 1/4″ in the largest size. The style has a very close-fitting bodice, so negative ease means that the garment must stretch from the back around to the front in order to fit; the side-seams won’t sit at the side of the body. For Felicity (right chart) the amount of pattern ease, and the way it increases as the sizes increase, makes total sense. As Kathleen Fasanella explains in her Entrepreneur’s Guide to Sewn Product Manufacturing: “as people get bigger, they get proportionately bigger“:
The other grade rules are more subjective to personal choice, as they affect the shape of the design between sizes, not just the basic circumference of the garment, or what size to choose. Let’s look at the measurement rule used to grade the height of the side-seam.
In Hummingbird (left), the bodice height grades from the top corner point of the side-seam, at 1/16″ (the bottom corner is set to grade zero). In Felicity (right) the bodice height grades at the bottom corner of the side-seam, at 1/8″ (the top corner is set to grade zero):
In Hummingbird, the smallest size side seam measures 43% of the bodice height…in the largest size, the side seam measures 36% of the bodice height. In Felicity (right), the smallest size side seam measures 56% of the bodice height…in the largest size, the side seam measures 53% pf the bodice height. Felicity has a side-seam height more consistent to the sizes throughout the range, while Hummingbird has a side-seam that gets progressively comparatively shorter as the sizes increase. I’ve always been bothered by the skimpy side-seam in Hummingbird in the larger sizes, so I’m preferring Felicity in the larger sizes here.
However there is a trade-off: the armscye shape in Hummingbird is more consistent throughout the size range, while in Felicity the armscye seems to flatten as the sizes decrease. This is probably the best example of the human factor in grading: Illustrator or CAD are just the digitizing tools. The grade rules entered are the human element.
So in Hummingbird, the bottom corner of the side-seam was set to grade at zero; in Felicity the top corner of the side-seam was set to grade at zero. To my eye that results in the Felicity armscye shapes changing between sizes. If I slide the size 4 armscye up to the size 12 (left) the 12 seems to have a deeper shape. If I slide the size 4 armscye down to the size 6 months (right) the 6 months seems to have a shallower shape:
Personally, I would prefer increasing the grade rule for the point at the top of the side-seam from zero to 1/16″ (as in Hummingbird). This would (in my opinion) make the armscye shape more consistent between sizes:
I’m pretty happy with the result: the armscye shape is consistent, and the side-seam height in size 12 is about double that of the 6 months:
Alternatively, I could have taken Hummingbird, and simply regraded the bodice width to better match the body-size-chart with consistent ease:
In the end, what I’m going to use for my next sewing project (a nightie for a little girl who wants sleepwear that “looks like Mommy’s”) is a mash-up:
- bodice width grading of Felicity with adjusted armscye grade as above
- graded neckline of Hummingbird (Felicity neckline CF is graded to zero)
- strap placement of Hummingbird (1/4″ further from CF than in Felicity)
Here’s mom’s gown….and some samples I made for her 4-year old daughter:
I hope you can see from this comparison that whatever method a designer uses to grade patterns, the most important element is what information is put in: the grade rules that the designer chooses to get the fit and design shape she wants, across the entire size range.