Poll of the day: True Bias

Sucker for punishment that I am, here’s another quiz you can argue with me about. I’m doing this one a little different. For advanced visitors, you can read the question, pick your answer and boom, you’re done. For those new to the topic, immediately following the poll, I’ll do a little background so you can understand the question and hopefully go back to answer the question. I hope it meets with your approval.

Of the two layouts below, which pattern is lying on true bias? The left or the right? Assume both the pattern and the fabric are lying face up.

Edit 11/23/12
Vizu polls have closed down. Below is a screen capture of the poll results.



Cheat sheet on grainlines.

  • Crossgrain. Fabric is woven to specific widths. The side to side width is called “weft”. I remember weft by saying “weft to wight” which is how the shuttle runs. The side to side or weft is most often called the cross grain. When someone says “cutting on the cross grain” they mean that the lengthwise portion of the garment is aligned to the fabric threads running weft to wight.
  • Straight of grain. The threads running in the opposite direction (vertically) are called the lengthwise grain or straight of grain. It is traditional to lay garment pieces so that the vertical length of garments is aligned with the vertical running of the threads. A garment laid on the lengthwise grain is shown below.
    • True Bias. Sometimes, garments are laid across the cross and lengthwise grains at a 45 degree angle. This is called bias. Bias can run on a 45 degree angle two ways. The optimal direction is called true bias because it gives more than the other direction. True bias (and the other grains are) is shown below:

    To answer the poll question, all you need to determine is which top is laying on the true bias. One is lying on the bias, the other on true bias. You don’t need to understand sewing or marker making to answer it. The poll only requires spatial ability.

    Immaterial to this poll question is that lengthwise threads are under greater pressure, the lengths will shrink after cutting and washing. All enterprises are set up to manage this, sometimes it’s the bane of our existence but it’s one of the constraints of our work.

    Contrary to popular belief, the cross grain is more stable than the lengthwise grain, the side to side threads aren’t stretched like the straight of grain. However, it is more economical to cut on the lengthwise grain, also you have infinite length at your disposal.

    Premium, designer and bridge apparel is often cut on the bias. Bias is the most difficult grain to manage but the drape this cut permits is incomparable. Fabric flows smoothly and dramatically around the figure. Because it uses the most fabric (and requires more advanced pattern making and sewing skills) it is the most expensive to make.

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26 comments

  1. “Contrary to popular belief, the cross grain is more stable than the lengthwise grain, the side to side threads aren’t stretched like the straight of grain. ”

    Really? That runs counter to what I have read and learned in classes (mind you, I’m not saying that the writers/teachers were textile experts). I would have thought that stretching the yarns in the lengthwise grain would make them stronger. I’d love to read a post about the physics of grain, if you haven’t already written one. If you have, well, I’d better get searching.

  2. J C Sprowls says:

    A side mention: cutting on the cross-grain is also referred to as “railroading” the fabric. Imagine the selvedges as railroad tracks on the table.

  3. Alison Cummins says:

    Interesting. How do you distinguish bias from true bias? I was taught that ‘bias’ was anything different from 180 or 90 degrees, and that ‘true bias’ was 45 or 135 degrees. Clearly a different meaning than the one you are using.

    I was taught that both the cuts you show are going to drape differently on the left and right sides. On one side the crossgrain will run from shoulder to center bust (more or less), on the other side it will be the lengthwise grain which will create an asymmetry in the garment.

    Further, I was taught two ways to avoid asymmetry. Either create centre-front and centre-back seams and lay the pieces out herringbone-fashion, or drape. Centre seams and herringbone layout give symmetrical pattern pieces, symmetrical bias, and a symmetrical garment; draping takes into account the asymmetry of the bias around the body and will generate asymmetrical pattern pieces, asymmetrical bias… and a symmetrical garment.

    I gather this is a different post entirely?

  4. O.K. I’m going with the one on the right, but will admit that I don’t exactly know why I’m picking that one. I think the one of the left would pull funny, but I’m stumped to explain my answer, even to myself. Maybe I’m just crazy.

    I’ve always liked to cut sleeves using the crosswise grain. It was explained to me at some point that this makes the most sense b/c it mimics the grain of the body of the garment if you’ve used lengthwise there, but honestly, I use it because the cross grain, in my opinion, works better around the elbow, not going up and down it. My methods are mostly stuff I’ve just worked out on my own,though, so take that with the grain of salt.

  5. Kaaren Hoback says:

    My personal preference for custom one off garments would be to cut with the grain “chevroned” or herringbone as mentioned by an earlier poster with a center front/back seam rather than single lay unfolded full front or back. I suspect that for multiple lays the front would do best on true bias (to the right)but the back should then be cut on the bias ( to the left) carefully maintaining the same exact angle not just off grain. I have never cut multiples in stacks on bias- so look forward to a correct explanation.
    Kaaren Hoback

  6. Kathleen says:

    Re: what Allison said. We must have had the same teacher. Then I found another one. Her name was Vionnet. :)

    Btw, the incorrect answer was copied from a book. The person who sent it to me said she found that example in three text books.

    Gorgeous said:
    I would have thought that stretching the yarns in the lengthwise grain would make them stronger. I’d love to read a post about the physics of grain, if you haven’t already written one. If you have, well, I’d better get searching.

    No, I haven’t written anything on the physics of grain but there’s plenty about the instability of the length of grain ad nauseum, endless endless discourses in trade texts regarding the management of this. Fabric shrinks more in the lengthwise grain. Were the latter more stable, it wouldn’t shrink to the degree it does.

  7. Claire G. says:

    I’m also surprised by Kathleen’s statement about cross vs. lengthwise grain. It seems that when I pull a fabric on the crosswise grain it stretches more, so for example you could do a close-fitting skirt with no darts. But maybe this stretchyness has nothing to do with the stability of the crosswise grain i.e. the amount it shrinks?

  8. Patricia Smith says:

    I am gonna ‘guess’ the one on the right, because that would put the true bias grainline running parallel with the center front-center back lines of the garment. However, also confused…because if the layouts are single and there is a selvedge on both edges, why is the ‘true’ bias only from NE to SW…why wouldn’t the bias that is 90 degrees to this line not also be “true”? I suppose THAT is the tricky part?

  9. dawn says:

    I guess it depends what you mean by “stable” in regards to the cross and lengthwise grains. I always thought of stable as non-moving or rigid. You can feel that most fabrics have less give lengthwise than crosswise. It makes sense now that you say the lengthwise threads are stretched in the weaving process. That leaves more stretch in the crosswise fibers. It also helps explain why they shrink more lengthwise with washing. But it still makes sense to cut garments with the lengthwise running up and down. Imagine if they shrunk more around!

  10. massa says:

    to answer this quiz, I just thought if I folded the fabric at true bias, how I would place patterns not to waste the fabric. I chose the one on the right. For 135 degree, I will choose the left one.

  11. tina says:

    As a former weaver and a long time sewer, a garment cut on the bias has the 45 degrees flowing down over the body. Intuitive physics tells me that gravity pulls the bias evenly down from shoulder to hem, assuming you are standing upright of course. The full magic of the bias is… you utilize the entire range of stretch available in combination with gravity. The cloth as it lays over the body can undulate from a straight fall to rolling smoothly over curves. And it rolls smoothly because the 90 degree grid collapses and expands as it and you move.

    I usually envision the expanding and contracting movement of those old wood accordian gates that used to keep toddlers from falling down the stairs.

    Now, exactly why that doesn’t happen with the 135… I can’t quite get there because it is time to sleep.

    The stability of warp threads (grain direction) in comparison to the weft (crossgrain direction) can vary depending on the weave structure. On the loom the warp threads are under tension/stretched and the weft threads snake over and under. The crossgrain has more give because each weft thread is longer than the horizontal distance it travels. After finishing, the warp threads relax and shorten. However, different weave structures, with different amounts of deviation in the path of the weft will create different shrink rates.

    The strength of the warp threads is a slightly different issue. Usually the warp thread is stronger to begin with because it must withstand the constant beating of the weaving process.

  12. Alison Cummins says:

    Ok, what I don’t get is how come:

    A: It’s ok to cut a tank top with the crossgrain going from my right shoulder to centre bust and the lengthwise grain going from my right shoulder to centre bust, because this is true bias and will drape better.

    B: It’s not ok to cut it with the crossgrain going from my left shoulder to centre bust and the lengthwise grain from my right shoulder to centre bust because this is just bias and will not drape as well?

    Because I can convert A to B by turning the garment inside out. The garment itself doesn’t change, but the right-side-out one will hang evenly and the wrong-side-out one will not?

  13. Connie says:

    True bias is a 45 degree angle from the selvage so I voted right. Somehow, being right handed, I would intuitively choose the right anyway,and not the left. The true bias is supposed to have the most give. Has this been proven scientifically?

  14. tina says:

    Alison
    Exactly. I also do not see a difference. Why does it matter if grain travels left to right or right to left across the body? What is is missing here? Are we in some strange version of “Flatland” here?
    Tina

    ps if you haven’t read Flatland-do. a world which is points, lines and planes only. So the line manifests as a line or a point. A square changes in length of line, but is never seen as a point A triangle is seen as the same length line
    from all views…Of course the women are at the bottom of the heap

  15. Oxanna says:

    I’m not quite sure why the direction would matter, but I picked the one on the right, because if you rotate the piece (or the grainline) to the right in accordance with the direction of true bias that you gave, you end up with the pieces looking like the right layout. If you wanted to avoid any asymmetry problems, you would do as others have said and put in a center front and back seam.

    I should dig out some of my textbooks to see what they say. I seem to remember them saying that either 45 or 135 degrees is true bias, but I could’ve just been assuming that all on my own. :)

  16. Deanna says:

    I picked the one on the left because I thought that the true bias is the direction of most give in the fabric, therefore it is most useful having that give around the body. The length of the garment would be somewhat more stable. Is it something to do with the direction of the wrap of the threads when spinning? I can’t remember the term but it can coax the fabric to twist or lean in a direction.

  17. Kaaren Hoback says:

    As a hobby hand weaver and spinner since the 1960’s and one of Those people who dives off on tangents- this is what I think I know-

    The direction of twist in a yarn using sheep’s wool creates either a woolen or a worsted. The cleaned fleece is also carded (combed) differently. Twisted one way the yarn spins softer, the other direction harder and stronger. When the yarns are plied together to make a “yarn” they are plied (several strands twisted together) in the opposite direction of the twist when spun.

    When hand weaving the warp thread is generally intentionally stronger and has more twist per inch than the weft ( also called woof) yarns. The weft threads can be “loftier” with more air and less twist so it “fills” the cross wise space. The lower twist creates a softer hand yardage.

    Cottons, silks and synthetics all have different properties when being spun or reeled or extruded, and often need chemical treatments and coatings to become modern fabrics.

    Griege ( gray)goods ( not yet dyed) but often pre treated for color application also get heat, wet or dry chemical treatments which effect the stability of the yardage.

    Considering the variants possible in the texture and tightness of spin of the warp and weft threads or yarns might be why there is endless discussion and some controversy about the stability of the long and cross grain.

    Having been bold enough to say that- my experience says the probable increased starting strength of the warp(long) threads generally is more stable than the lighter spun weft or filler threads. When preparing and testing fabrics I often pull a few weft and warp threads both before and after laundering or dry cleaning to see how they behave once the chemicals are cleared off.

    Kathleen – If I have gone too far off topic my apologies
    Kaaren

  18. Todd Hudson says:

    Right layout. If the true bias runs up towards the right hand (I imagine this fabric has a diagonal weave rather than a plain weave), then you should align the center front and center back lines of the pattern pieces along the same angle as the true bias as in the right layout.

  19. Rita Yussoupova says:

    If the garmets are cut as on Right image the CF and CB lines of the garmnet are aligned with True Bias line of the fabric as marked.
    If the garments are cut as on Left image the True Bias line of the fabric is alined across across the garment.
    Thank you Kathleen we just do not have the time
    to think about important things and pick them a part. Great little brainstorming challanger.

  20. Rita Yussoupova says:

    If the garments are cut as on the Right image the CF and CB of the garment will be aligned with True Bias line as marked on the fabric.
    If the garments are cut as on the Left image the True bias line of the fabric will be in the direction across the garment.
    Thank you Kathleen – Great little brainstorming challenge.

  21. Sue Tenney says:

    I’m no expert on bias, but I selected the one on the left. My impression is that fabric has the best drape on the true bias; with this blouse, I would want the best drape at the lower hem edge, not up in the neckline/armhole area. By my read, the left layout places the best/true bias at the lower edge of the blouse.

    That said, how does one figure out the true bias on any given piece of fabric yardage?

  22. jinjer markley says:

    okay, I thought this was going to be an easy quiz, but I’m baffled. here’s how the answer confused me:

    I was understanding that BOTH 45 degree angles are true bias, but that in order for a bias garment to hang correctly without twisting, the front and back should be rotated 90 degrees respective to each other. So my answer would have been “both” and “neither”

    In addition, my education is that “bias” aka “garment bias” means any angle other than along a grain (crossgrain or lengthwise grain” and “true bias” means 45 degrees from either of those grains.

    The third reason I’m confused is that this is a symmetrical pattern, so in a sense, it doesn’t make a difference which of the two examples you choose. Either the left hem corner will stretch/relax more or the right hem corner will. So what’s the difference?

  23. batel says:

    I can to this website to get a answer on how to layout and cut on the bias. the way the arrow is going accross the fabric I would bellive true bias would be the diagram on the right. please tell me so I can cut out my slip.

    Batel

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