The Denim Weave Process by William Kroll of Tender Co
Traditional blue denim is a cotton twill fabric, woven from a yarn-dyed indigo warp and a white or raw cotton weft (fill). Weaving involves feeding the horizontal yarn, the weft, between the vertical warp yarns- at its most basic the first line goes over one/under one/over one etc. This would give you a plain- (or a basket-) weave. If you use two different colour yarns (e.g. indigo and white) in a plain weave you get a cloth which is an even mix of blue and white on both sides. This is how chambray is made:
On a twill fabric, rather than weaving over one/under one/over one as in a plain-weave, the weft is passed, for example, over two/under one/over two etc. This pattern would make a 2-by-1 twill. On a twill fabric woven with indigo warp and white weft, this means that one side of the cloth is two parts blue to one part white, and the other side is two parts white to one part blue- this is why on a pair of jeans the inside is a different colour to the outside.
The pattern of weaving can be adjusted to make different twills, for instance 3-by-1 (over 3/under 1) 3-by-2 (over 3/under2) etc. This arrangement is slipped along in every horizontal line of weaving, so that the cloth doesn’t fall apart (in the same way that bricks are laid one row slipped across half a brick-width from the row below it, to keep the wall from falling down).
Looking at a piece of denim fabric, the twill line is the diagonal textural stripe created by this slip in the weaving lines. On the front (mainly blue side) of the denim, this is a blue diagonal spaced by the thinner white weft showing through. On the back (mainly white side) the diagonal goes in the opposite direction, and is mainly white, picked out by the blue warp from the front.
Depending on how the weaving pattern is set up, the fabric twill has a different ‘direction’. The most popular direction of twill for denim (traditionally used by Levi’s, and also for Tender’s jeans) is a right hand twill. Looking at the fabric lengthways, on the blue side, the diagonal twill line goes from top right to bottom left. Due to the way that the yarn which the fabric is woven from is originally spun, right hand twill fabric twists the yarn tighter during weaving, creating a ‘harder’ and more robust cloth.
While Levi’s used right hand twill denim for their jeans, Lee traditionally used a left hand twill fabric. This is made in basically the same way, but woven in the opposite direction, so that looking down the fabric the twill line runs from top left to bottom right:
Weaving in this direction causes the yarn to untwist slightly, resulting is a softer, more drapey fabric than a right hand twill woven in the same pattern from the same yarn.
Just as a rubber band twisted up and let go will quickly unwind itself, so the twisted cotton yarn used to weave denim ‘wants’ to revert to its original straight format. Depending on how the fabric is woven this will express itself in different ways:
Right Hand Twill Jeans
Left Hand Twill Jeans
In the photo above left, the English-made Tender Co. type 130s, cut from right hand twill denim have twisted after a year or so of wearing and washing. You can see that on the left leg (as worn) the outside leg seam is on top, and on the right leg the inside seam is on top. Looking down at your legs while wearing these jeans, you’d be able to see that the legs have twisted clockwise from their original parallel construction.
The 1970s US-produced Lee Riders, in the photo above right, are made of left hand twill denim, and have twisted anti-clockwise. This is because the fabric is woven in the opposite direction, and so untwists correspondingly.
‘Loomstate’, or raw, denim will twist at the first wash. Tender’s 130 jeans cut from loomstate right hand twill 16oz Japanese selvage denim will be hot soaked for The Buttery Store, and so will already have shrunk and twisted. Today, denim purists enjoy the character that this twist brings to the garment (also visible in ‘roping’ at the hems), but original jeans manufacturers were keen to solve what was seen as a problem with the fabric.
While yarn or fabric treatments such as sanforization could control leg twist to a certain extent for Levi’s and Lee, the third of the ‘big three’ jeans brands, Blue Bell (later Wrangler) devised a different solution to the leg twist dilemma. Wrangler’s signature broken twill denim is a pattern where one line is woven to the right, and then the next is woven to the left. This creates a fabric which tries to untwist first clockwise and then anticlockwise, all the way down the garment, balancing itself out so that the cloth remains stable and the garment construction seams stay parallel, even after years of wear.