Grading stretch knit patterns pt.2
Behind the scenes, I’ve been trying to learn screen capture video (again) which will be so helpful to explain things. For example, below is a short video on how to adjust shrinkage or stretch properties (it is the same thing) for a pattern. I used StyleCAD but any industrial CAD program provides the same function.
The matter of knowing what percentages to use to attain a given grade -say 2″- is but a bit of math or even, iteration. When I’m not so pressed for time, I’ll do a video on that too and post a link accordingly. In any event, the video is useful because you can see that if a service provider needs to adjust your pattern for shrinkage, it is fairly straightforward.
And now onto comments from the first entry:
Several people asked whether this process could also be used for grading wovens. I suppose it could be possible -it would be just dandy because it is easier- but there are a variety of problems one could have. It would be good to know what the limitations are so one could work around them.
Problem #1: Measurements are relative. For example, you want to grade this pattern (clicking on the image gives you a larger version):
Not to get off topic but this style is from Vionnet; I’ve been working with this style for years. At right is a picture of the style (from the Japanese pattern book).
The problem with growing this pattern as we do shrinkage or even knit grading is that the shrink and grow function (the little t-shirt tool in the video) won’t discriminate between garment sections. Or I should say, not as well as I would like or maybe I just don’t know how to do it (a distinct possibility).
Say you want to grade the above design to make it an inch smaller in girth. The program will make it an inch narrower (the program will adjust by measure or percentage) but this will be based on the widest portion of the skirt. So the skirt will be an inch narrower but the bodice, proportionately nothing. To have the bodice waist (the yellow line on the pattern piece) shrink an inch would take some math or even, iteration strategy. When I first tested Stuart’s method, I had to use an iterative process to make sure I understood it. Once I got the results I wanted, I copied the percentage formulas from that.
As impossible sounding as I make this out to be, it may end up being what I will use to grade a bias pattern that is very similar to this one. I have also been able to reverse engineer these grades or maybe I already said as much in the previous entry. I tell you, your memory goes when you get old. Either way, it is possible.
We have limitations that are imposed by findings and guts. Jalene alluded to this in her description of elastic widths but the same concept holds for widths of trims of any kind, including zippers. And sure, there are work arounds. For example (since I’ve played with this quite a bit), I have to change my drafting process to avoid complications. Specifically, I typically draft in the zipper extension as opposed to adding it like seam allowance. If I use this process, I can’t do that because the zipper sew down allowance should not change no matter how large or small the garment gets but it will if I use the shrink/grow tool (in CAD, seam allowances remain static). To adjust for trims that are of fixed widths (vendors only sell them in given sizes), one would have to do much the same and then go back to correct any notch placement.
Indirectly, Izabelle’s problem with the woven collar stands and plackets on knit shirts reminds me of a related problem. Consider rib knit collars for polo shirts; those collars only come in set lengths and the edges are clean finished rather than sewn so it will be a trick to grade knit shirts to match the pre-made collars provided by a trim vendor.
Styling details. Pretend we have a blouse with a cut-on tie at the neck. If we stretch grade this, the tie will get larger proportionately and would probably look wonky. The issue is really that as people grow larger and smaller, they’re not considerate enough to do it proportionately (akin to knits). For example, as a woman gains weight, she could disproportionately (as compared to knit fabric) gain more girth in the bust. With traditional grading, we can put the grow where we need it. With knit shrink grading, it would be evenly and proportionately spread across the pattern piece.
I’m sure there are other limitations to using shrink grading for wovens but I’d rather not come off as defeatist. I actually think this concept is ripe for exploration and testing, and I plan to do more of it. I’ll report back as I’m able.