[NOTE - this article applies to those who knit either English or Continental style. Both are considered "Western Knitting", and proper orientation of a knit stitch is where the right leg of the stitch is on the front needle. If you practice "Eastern Knitting" where you knit and purl in reverse, and the left leg is on the front needle, the below article will not apply.]
Unintended bias in knitting causes a garment to twist to one side in a spiral nature and is caused by too much twist in the yarn. This is more common in inelastic yarns like cotton and in yarns that are 2-ply. In wool blends yarns it is most often caused by the yarn being overspun.
Z twist yarns rarely give us trouble with creating bias. It’s the S twist yarns that are the culprits. This is because when a yarn is inelastic or twisted too tightly and you knit it, the very process of wrapping the yarn around the needle for each new stitch adds more twist to an S twist yarn. Knitting removes twist from a Z twist yarn. When the twist tightens, the entire fabric will slant or skew to one direction, which ends up wrapping around the body if you’re knitting a garment. If you've ever had a cheap t-shirt or cotton shirt that twists, this is why. The side seam ends up swirling around to the front and back of the top and it just won't hold straight no matter what you do it.
It doesn’t matter whether you knit English or Continental style, because when you knit either style, the yarn is traveling around the needle in the same direction. In Continental style, your fingers make smaller movements and the needle moves around the yarn instead of guiding the yarn around the needles with your fingers which happens in English style. But when you examine each in slow motion, you’ll see that the yarn is wrapped counterclockwise around the needle in both methods. Once you've knit a stitch, the right leg of the stitch will be on the front of the needle and the left leg of the stitch on the back of the needle.
Bias is more noticeable in Stockinette stitch. When you incorporate a combination of knit and purl stitches, it can help but not always. Cables can actually increase the bias because of the extra tightness that occurs when forming them. Working in twisted stitches can cause more twist as well which is what we are trying to avoid in overly twisted yarns.
If you’ve wound your own skein and are pulling from the center, pull out a foot of yarn and hang it next to a foot of yarn from the outside. The yarn in the center may be pulled tighter than the yarn at the outside, because when you’re first getting the swift going, if you allow the ball winder to pull yarn from the stationary swift, it will stretch tightly at first. Once you get some momentum going and less yarn is on the swift, you’ll notice that the tension eases off. However, this is not causing the bias.
When you examine two pieces of yarn, one from the center and one from the outside of the cake, the center strand may be pulled tighter but the amount of twist remains the same. Once you remove the tension from the center, both strands should lie the same. If you just pull on a strand, it makes it tighter, but doesn’t affect the twist. The amount of twist can be determined by looking at the number of crosses that one strand makes on the other. The closer the diagonal lines are together the more twist you have. Measure out about 6” of yarn from the center of the skein and 6” from the outside, then count the number of diagonal slants in each piece. If they are close to the same then you have the same amount of twist in each end of the yarn.
More often than not, the root of the problem lies with the way the yarn is spun before you buy it. Bias cannot be steamed out. Severe blocking may help, but once the fabric is dry it will have a tendency to skew again. Knitting flat & seaming the sides is better than knitting in the round but again, it will not eliminate it.
The correction needs to be made during the act of knitting.
For overspun yarns, one easy, but time-consuming method is to pull out a yard or so of yarn, take a clothespin and clip the yarn to the ball. Let the ball of yarn hang from the work so it untwists itself, then knit normally from the untwisted yarn. Or by hand, untwist a section of yarn, clip it to something (pillow, blanket, your shirt, anything really), and knit until you reach the clip. Then untwist another section and keep doing this. Eventually you’ll need to let the ball spin itself back to a normal position.
Another better, faster remedy when working in Stockinette is to wrap the yarn in the opposite direction (under and clockwise instead of over) when forming the purl stitch on the WS rows. Then when you’re working the RS rows, knit each stitch through the back loop. This untwists the yarn and you’ll notice instead of a tightly swirled S on the needle, you’ll find a very loose one that almost resembles a single ply. If you’re working with 2 ply yarn, instead of a twist on the needle, you may actually see both plys squeezed together and lying almost side by side, with just a little twist between them.
If you’re working in a combination of stitches this becomes a bit trickier, since the front & back of the same stitch need to be altered in order to reduce the amount of twist in the yarn, and at the same time prevent the stitch from becoming twisted. A twisted stitch has the bottom two strands of the V crossed. When you pull the stitch apart, instead of the V opening up at the bottom, you’ll see the strands crisscross and become tight. You do not want twisted stitches (unless the pattern calls for them in the design.)
By wrapping the yarn around the needle the wrong way (clockwise) when making a purl stitch, and knitting through the back loop when knitting this same stitch on the next row, you are orienting the stitches on the needle so that the left leg is at the front of the needle and the right leg is at the back. This is opposite of how stitches are normally oriented. If you were to only do one of the two, for example, knit a stitch through the back loop, then purl it normally on the WS row, you would have a twisted stitch. But since you’re knitting through the back loop on the RS AND wrapping the yarn around the needle clockwise when purling on the WS, both actions counter each other out and the stitches remain untwisted. And you are accomplishing your task of untwisting the yarn every time you work a stitch.
Most of the time we don’t realize we have a problem until we’ve knitted a few inches and the fabric begins to slant. If you notice that the yarn is kinking and doubling back on itself, that’s a sign that it’s spun too tightly. Removing some twist at this point may save you time in the long run. Watch the yarn as you go though. Sometimes you'll find sections of yarn with a tighter than normal twist, then it evens out.
I hope this tip helps and that it brings some answers to the puzzle of unintended bias. An ounce of prevention is worth a pound of cure, and if you can fix the problem as you knit you’ll be able to continue creating a garment that you can be proud of.
“Adding twist to splitty yarns." 07MAY18. <https://yarnsub.com/articles/techniques/adding-twist/>