Grading stretch knit patterns pt.2

Posted by Kathleen Fasanella on Nov 21, 2013 at 4:49 pm / Patterns, Textiles and Inputs / Trackback

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):
wovens_graded_like_knits1sm
vionnet_japanese_book_pattern19
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.

Problem #2:
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.

Problem #3:
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.

11 Responses to “Grading stretch knit patterns pt.2”

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Kathleen
November 24th, 2013
5:55 PM

I must say that the tepid response to this post is not convincing me to shell out the big bucks to buy the screen capping program after the trial ends. Or was it something I said?

Lara
November 25th, 2013
6:35 AM

Please keep posting about grading stretch knit patterns. I’m a regular reader of yours and find this so interesting–especially since I favor sewing with stretch/knits fabric. I don’t use pattern software (yet) so this truly is helpful to see for when I do. Thank you for all the information you share.

Theresa in Tucson
November 25th, 2013
7:47 AM

Not anything you said, Kathleen. I didn’t comment because the post was on knits, and I don’t wear or sew knits so mostly ignore posts that discuss them.

JustGail
November 25th, 2013
7:50 AM

There’s a *lot* to think about and ponder. At least for me. So in the above example, you are wanting to change the waist by 1″, but not neccessarily change the skirt by the same percentage? IE, if the original waist was 25inches, you want to reduce that by 4% if my math is right, but not decrease the skirt (lets say it was originally 120 inches across) 4% which would be 4.8″. As you said, unless there’s something in the CAD program, the only way I can see is to divide the pattern pieces, apply the desired grading to each section and then true up lines and rejoin the sections. But I’m going to guess that will most likely open up another whole can of worms?

Regarding the screen capture – I had to keep clicking the progress bar at the bottom. Like every step was it’s own little snapshot. Also, is there sound? It was a bit hard to figure out what you were doing the first time watching, after figuring out the “keep clicking” and watching a couple times, I got it. If sound is not an option, is there a way to add captions? I have used a couple of drawing/simple cad programs, but if someone had never used one, it might be a tad frustrating. Other than those 2 items, it seems a nice touch.

Kathleen Fasanella
November 25th, 2013
11:13 AM

Gail: Correct, one can do all of that (figure the math out and or break up pieces) but then the operation becomes more work. Not that this is a problem, only that the original proposition was to use stretch grading techniques to quickly grade wovens. As a practical matter, your suggestion was my first approach (prior to publishing the post) to grading this (actually, scaling it). I still want to play with it some. I had planned to show a test sample sewn up but I messed up the cutting something awful (my fault too).

About the video. I was having very similar issues such that you describe. I updated my flash player and it all went away. The next day, I was having problems again so I checked Flash and it was okay but my browser (FF) needed updating. Since then, I haven’t had any issues. It would be useful tho if you could let me know if any of this helps.

Oh, one other issue. There may have been a lot of traffic either on this site or on youtube.

Shelley
November 26th, 2013
12:05 PM

I really found this fascinating because I use a home level pattern software that uses percentage shrinking for knits after you’ve decided on what ease you like. The idea being you’d still have that same fit after the percentage reduction for whatever knit ( the percentages are grouped for ease of use) we chose.
This software also has a CAD type editor and the way you’re demonstrating could be done too. Neat. ; ) As for the low traffic, could be the holidays. I’m commenting only because I’m waiting on some work, did my Thanksgiving grocery run, have sale shopping planned and have no kids to watch anymore.
I had no problem with the video, btw. If it is easier for you, it’d be great to see more.

Lin
November 27th, 2013
7:55 AM

I am very new here I just bought the book but have not received it
Helping my daughter with a web based baby clothing line
This is way over my head so far ,

Teijo
November 27th, 2013
9:46 AM

Higher end CAD programs allow the operator to set constraints that keep dimensions that should stay static from changing, and/or define parts that should stay proportional regardless of other changes. Perhaps this feature is also available in pattern oriented cad packages.

Amy
December 11th, 2013
7:17 AM

I, too, am fascinated with these posts. Especially as I am contemplating purchasing pattern software in the next year, it’s interesting to see what your outcomes are with this method and product.

I find that I don’t have much by way of opinion or observation to offer regarding these posts, perhaps because this method of grading is in many ways so different from standard grading practices that I have found in text books (and by this I must offer that I am a largely self-taught home-sewer so the grading methods I have learned are no doubt much different from what professional pattern makers typically do). So, I may not even be your target audience.

I read these posts and noodle them, but my brain hasn’t really caught upon any one concept, theme or idea that has resulted in a mental output. This is not much different to any other time I have taught myself a new skill – a person must keep making inputs and eventually things will start to codify into more abstract concepts and at that point the questions start popping out. The proverbial “learning curve.”

To the extent that I have anything to show so far, one observation I have from looking over most of Stewart’s website back when it was still active is that all of his clothing and drafts were for form-fitting garments where the entirety of the design required negative ease to one degree or another. And the fact that he worked (as far as I can recall) almost exclusively in very stretchy lycra swimwear (I am sure he used other materials over the course of his career, but that was the focus of his website). I wonder if this type of grading system necessarily has issues once a design no longer closely follows the human form, regardless of whether or not it is stretch.

In any event, thanks so much for posting what you have so far, and sorry I don’t have anything more insightful to add.

Kathleen
December 11th, 2013
3:48 PM

Since I wrote this, I’ve continued to experiment with it to include wovens.

It has proven useful as a guideline or cheat sheet with respect to complex woven patterns. What I’ve done is stretch grade the woven pattern to general parameters and then use the overlaying of sizes to create rules that the system will use officially [because it won't recognize copy/paste duplicates as separate sizes].

Frances
December 31st, 2013
8:37 PM

I’m trying to catch up and I looked at this entry on Dec. 31. I want you to know that the little video worked fine for me. What screen capture program did you use? Because I want one for another purpose and I’m confused about what program to get.

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