“Why are these pant legs twisting?” or “Why Grainlines Matter”
August 11, 2019
Whether you make your own jeans (bravo!), or purchase them ready-to-wear (me….), or want to know more about grainlines, this one’s for you.
Have you ever had a pair of ready-to-wear pants (especially jeans) where the seams twist around your legs instead of hanging straight down, and wondered “Why does this happen?” I was reminded of that today when reading this post in a FB sewing group:
Actually I’ve read posts online about this quite often, and the quick answer is that the fabric was cut off-grain:
But WHY does this happen in the manufacturing process? Often there are comments online that the pattern pieces were cut off grain because the fabric is cut in stacks andcan shift off-grain during cutting just as they would if you were cutting through multiple layers of fabric at home with scissors. This is one possibility, and along with inconsistent stitching between operators can cause a variation in fit within a single labelled size. But it’s most likely not the biggest cause of twisting. It’s an interesting question so I thought I’d explain what I know from working decades in the garment industry. There are 2 main reasons why cutting off-grain occurs, but shifting BECAUSE of the cutting process isn’t the major one. It’s far more likely that the problem happened BEFORE cutting, either because the fabric was already off-grain, or because the pattern marker was off-grain.
Take a look at this video (click on the link) and you’ll see that when fabric stacks are cut using an industrial cutter, the fabric shift is actually quite minimal:
So if that’s not it, what causes off-grain cutting? Backtrack a second to think about mass-manufacturing. Fabrics are cut out on a long table, with multiple layers of fabric spread out using a machine like this:
Once all of the fabric is layered, it is topped with a paper marker printed off of a computerized layout of all the pattern pieces in all of the sizes needed:
After laying the paper cutting marker on top of the fabric and weighing it down, the stack is cut using a jigsaw cutter (this video below is fascinating to watch!). Using a vertical blade ensures that the fabric shift is minimal through the layers. The fabric does not get pushed as it would when cutting with scissors (and to a lesser extent a rotary cutter).
Modern fabric cutting is done even more accurately with automated (not hand-guided) cutters, especially for basic garments made in enormous quantities like underwear, basic tees and jeans :
The latest cutting tables are equipped with vacuums underneath the cutting surface which even further ensure fabric shift does not occur :
The irony is that often it’s these very basic, made-in-mass-quantity items that should be made so accurately, that are often “twisty”. Why are these cut off-grain? Probably because the profit margins on basics (non fashion items) are so competitive that every penny gets squeezed. Here’s what can happen……
Possibility #1: The fabric was already of-grain before it was laid on the cutting table. Fabric that is “on-grain” has the lengthwise warp threads parallel to the selvedge (the factory-finished edge), and the crosswise weft threads 90-degrees from the selvedge:
When placing the pattern pieces on the fabric, the grainline on the pattern should be lined up with the warp thread lines, ensuring that the garment is cut “on grain” and hangs nicely without twisting. Exceptions are garments cut on the bias grain, or border-prints in which the pattern piece is lined up with the grain matching the weft threads.
What about fabric that is “off-grain”? Think about when you purchase fabric cut-to-measure at the fabric store. It’s never cut “exactly” on-grain, (unless it’s ripped-to-measure) because it’s always ever-so-slightly off-grain on the bolt. In general, better quality fabric is finished closely on-grain, and lesser-quality is heavily skewed because the manufacturer has skimped on the finishing process. Some of the most off-grain fabric I’ve ever used is JoAnn Fabrics “Symphony” poly-cotton, which is only usable IMHO after spraying with Downy Wrinkle Release, and s-t-r-e-t-c-h-i-n-g from opposite corners until the grain is at 90-degrees.
How does fabric get made off-grain anyway? In the weaving process the warp yarns are attached to the loom and the weft yarns are woven back and forth over and under at 90-degrees. When that’s done, the fabric is stored as greige (un-finished) raw goods, waiting for purchase-order instructions to be dyed or printed. (This is done to speed up manufacturing: it’s always faster to order greige goods and have them finished-to-order than to order fabric woven from scratch).
The greige fabric gets “finished” by being stretched on a tenter frame (that’s why you see those tiny holes along the fabric selvedge) to eliminate wrinkles, and then it gets printed, surface-brushed, etc. Here’s where the grainline problems can occur: if tentering isn’t done correctly, the fabric gets skewed.
Unlike in home-sewing, where you can true-up the grainline of a small yardage of fabric to 90-degrees with moisture and stretching, apparel factories have no time (or process) to do that. Imagine a standard 50-yard roll of SKEWED off-grain fabric is layered in multiples down an 18-foot cutting table….and then the paper marker is placed on top, and the patterns pieces are cut out with a vertical cutter. That is often how RTW garments get cut off-grain, with the result being garments what don’t hang correctly: the cutting is accurate but the fabric was already off-grain.
Possibility #2: The marker is tweaked, putting some pattern pieces ever-so-slightly off-grain to squeeze more garments out of less fabric and therefore make a better profit.
You’ve possibly been faced with this situation at home if you were challenged with less fabric than a garment called for, squeezing in the small pieces, sliding pieces together ’til the seam allowances slightly overlap, maybe ignoring the given layout altogether. Have you ever been tempted to slightly shift a piece off-grain to make the pieces fit in better?
How would a garment factory get away with that in mass production? When a “top-of-production” sample (T.O.P.) is sent to the tech designer for approval before mass production begins, it gets checked for:
correct measurements ( the garment specifications or “specs” may have dozens of details in finished-garment lengths and widths, and must be within stated tolerances)
What’s missing? Grainline. I’ve worked with dozens of apparel production companies and hundreds of factories, and never have I been required to approve a T.O.P. sample’s grainlines. It is assumed that the marker-maker will line up the grainlines accurately. Even if the T.O.P. sample is perfectly cut on-grain, when going into production this isn’t always the case, and they get away with it because the garment can meet the measurement targets perfectly while being off-grain.
You may wonder “What’s the point of squeezing more jeans out of the yardage? Doesn’t the factory buy exactly how much yardage they need for each order? What would the factory you do with leftover fabric?” Actually the factory, not the manufacturer who is hiring the factory, may be purchasing the fabric…so if they can quote a garment price based on x yards and show the marker to justify that, and then tweak the marker to require less fabric, they can order less.
Why is the factory (not the manufacturer) ordering the fabric anyway? Back when garment production for American consumption was primarily done in the U.S. (up until the 1970’s), department stores bought garments from manufacturers who purchased their fabric from domestic mills. In magazines you’d see advertisements for clothes indicating not only the manufacturer but also the mill:
Sometimes the mills themselves placed ads, without mentioning the manufacturer, just so that customers would look for that mill’s label when clothes-shopping:
Things changed in the 1980’s:
department stores lost business to the rise of national chain stores in suburban malls (The Gap, The Limited)
big box stores (WalMart, KMart, Sears, Target) started making their own label clothes directly through factories
American customers lost interest in mill names and sometimes even manufacturer’s brand names, instead shopping for store’s own label
trade was opened with Asia, moving manufacturing overseas
factories in Asia preferred to use local fabrics instead of importing them from American mills
For example when The Gap first opened they only carried brand name jeans…now their stock is completely “Gap” label brand. And just as the retailer can cut out the manufacturer’s brand name by making their own product, the factories can cut out the mills by sourcing their own fabric.
These days an American retailer/manufacturer doesn’t purchase the fabric (they are generally not interested in owning fabric stock, only garment stock). The retail buyer does not specify which mill the fabric must come, they only request the quality standards (content, weight, yarn count) and the garment factory provides swatches for approval, and then purchases the fabric from their choice of mills. And because of all that, factories may be tempted to squeeze more garments out of less fabric (improving their margins), hence cutting slightly off grain.
Other than being cut off-grain due to either the fabric itself being off-grain or the marker being tweaked, there are other factors that may contribute to twisting specifically in jeans..
SHRINKAGE: Not only do natural fiber garments shrink in length (and less so in width) when washed, they also “relax” from the stretched state the fabric was in while tentered…..and twill-weave fabrics have a tendency to curl to one side because of the up-over-down-over weave. Chances are that you are buying pre-shrunk (saforized) commercial-production jeans, however if you are purchasing high-end “raw” (unsaforized) denim, it is going to shrink a lot more after production….like 10% or so with the first wash and residual shrinkage after that, twisting more each time. Just the nature of “real” denim.
In the case of jeans, unless the manufacturer or the retailer tests for “spirality” (this is a wash-test that better makers use, but mass vendors usually not), the garments will pass inspection. Even if jeans hang well in the store, they may curl somewhat in washing, when the fabric relaxes and shrinks.
STRETCHING WHILE STITCHING: If you’ve ever studied tailoring or fine-sewing, you may remember being taught to always stitch from the wider end of a pattern piece to the narrower end, to avoid stretching the fabric. For example always stitch pant legs from waist to hem. If you study a pair of dress pants, the sequence-of-stitching will be inseams-then-rises: you can stitch the left leg inseam waist-to-hem, then the right leg inseam waist-to-hem, and then stitch the rises.
Now look at your jeans. Chances are the sequence-of-stitching was rises-then-inseams. Most likely the inseam was stitched UP one leg and DOWN the other. This can cause legs to stretch unevenly front-to-back causing torquing. Keep in mind that apparel mass production is done without pins; the operator holds the ends of the seams together and stitches halfway down the seam, then pinches the opposite seam ends together and stitches while stretching to make the ends meet.
And finally, jeans are notorious for twisty seams, first because the legs have long pattern pieces so anything off-grain is made worse, and second because they are meant to fit snugly so you are more aware of weird fit.
And that is how “twisty” production apparel gets into the stores. What does this mean for you as a consumer?
Try on every pair of jeans. Even if you are buying multiples, whenever possible try on each piece. Basic apparel items are usually made in several factories (in case one factory closes, goes on strike, etc) and each lot can be different.
Study grainlines. In denim they are pretty easy to see; make sure the legs have symmetrical grain left-to-right.
If you buy a garment and it skews badly after washing, return it and explain WHY. The retailer then knows to charge back the factory.
Note: If your jeans are made with raw “Selvedge” denim this does not apply because they will be more prone to shrinkage in the wash compared to commercially manufactured denim, which has been shrunk in length at the mill.
If you have an old pair of jeans that fits well in the waist and hip but the legs are irritating you, consider cutting the legs off to make shorts.
What does this mean for you as a sewist?
Check all pattern pieces for grainlines. If a pattern is missing grainlines, ask the pattern maker for advice. Usually in home-sewing patterns you can assume that pieces cut on the fold have the foldline as grainline (factory patterns are never cut on the fold….production fabric comes on rolls., not folded bolts)
Especially be careful of accurate grain in long pattern pieces such as pants and sleeves, which are never cut on the fold (or shouldn’t be anyway!!)
Check your fabric for trued grain (“true” 90-degree angle in the weave) and adjust your fabric before cutting if it needs to have the grain straightened (plenty of YouTube videos on that)
Place your pattern pieces on the grain accurately by measuring pattern grainlines equidistant from selvedges.
Avoid the temptation of squeezing pattern pieces into a too-small length of fabric by cutting off-grain! Use a different pattern, or make adjustments that won’t affect correct hanging (shorten a skirt, or take out some sweep for example….make capris instead of full pants)
Stitch all seams from larger-area to narrower-area to avoid stretching
Be thankful that you can sew exactly what you want, the way you want it! Personally I don’t have the patience to sew jeans, but I applaud all of you who do.