A pair of knit pants comes out of the dryer with the side seam no longer down the side. It has wandered toward the front of the leg and taken the whole leg with it, so the pants look like they are turning as you walk. A plaid shirt does something similar, with the hem riding up at one hip. The usual assumption is that the wash did it. The wash only revealed it. What is happening is a disagreement between how the cloth was cut and how the cloth wants to lie, and water is what settles the argument.
Grain Is A Right Angle
Every woven cloth has a lengthwise grain and a crosswise grain. The lengthwise grain follows the warp, the yarns that run the length of the roll between the two selvedge edges. The crosswise grain follows the weft, the yarns that travel back and forth across it. On grain means those two sets meet at a true right angle everywhere in the cloth.
A right angle is not guaranteed. Cloth goes through dyeing, washing, drying and finishing on rollers, and it travels under tension the whole way. If one side of the roll is pulled slightly ahead of the other, the weft no longer runs square across. Pulled evenly out of square it is called skew. Pulled into a curve across the width it is called bow.
Both are measurable faults and both are common, especially where speed of finishing matters more to a mill than squareness does. A small amount is normal and nobody notices it. Past a few degrees it becomes visible in the finished garment, and on a plaid or a stripe it is visible in the cloth before anything is even cut.
Heat setting can hide it. Pass a skewed fabric through heated rollers and the fibers are pressed into their current positions and cooled there, so the cloth looks and feels square on the bolt. The skew has not been corrected. It has been held in place by a finish, and a finish is the first thing a wash takes off.
Water Lets The Cloth Relax
A cloth under no load wants one particular arrangement, the one with the least strain in it, and in that arrangement the warp and weft cross squarely. Hold it in any other arrangement and there is stored tension in the yarns, waiting for a chance to release. Washing is the chance it has been waiting for.
Wet fiber is the key. Water swells cotton, rayon and most other plant based fibers, and swollen fiber is softer and more mobile. Friction at the yarn crossings drops, the finishing resins soften or wash away, and for a while the yarns can slide against each other. The cloth is briefly free to rearrange itself.
Add a tumble to that and the rearrangement happens in one go. Tumbling works the cloth in every direction at once, which is exactly what a skewed weave needs in order to shift back toward square. Then the dryer takes the moisture out, the fibers stiffen, and the cloth sets in its new and more relaxed shape.
That is the whole mechanism. The garment did not twist. The cloth untwisted, and it was cut as though it had never been twisted in the first place. Each wash after that moves it a little further in the same direction until the cloth has fully relaxed, which is why the problem worsens for the first several washes and then stops.
How It Shows On The Body
On a pair of pants the clearest sign is the side seam. A leg is a tube built from two pieces whose seams should run straight down each side. If the cloth they were cut from rotates as it relaxes, the seam travels around the tube in a slow spiral, sitting near the front at the ankle while it is still at the side at the hip.
On a shirt the same thing reads as a hem that is no longer level, a sleeve that hangs with a built in turn so the cuff faces the wrong way, or a front placket that will not stay vertical. On a skirt it shows as a hem that dips in one place no matter how carefully the skirt is hung.
Pockets and plackets exaggerate it, because a patch pocket is a second piece of cloth sewn onto the first. If the pocket was cut on grain and the panel under it was not, the two relax by different amounts and the pocket bubbles or pulls at the corners. Topstitching along a hem does the same thing on a smaller scale.
None of these are wear symptoms. They appear on a garment that is otherwise new, they show up suddenly after the first proper wash, and they never improve with age. That combination is the signature of grain rather than of anything that happened in the laundry room.
A Cutting Fault, Not A Wash Fault
Cutting is where the fault is committed. A cutter lays pattern pieces on a stack of cloth, and each piece carries a marked grain line meant to be laid parallel to the warp. If the cloth underneath is skewed, that line is parallel to the warp and still at the wrong angle to the weft, and the error gets cut into every piece.
It can also be committed deliberately, by laying pieces slightly askew to fit more of them onto a width of cloth. Fabric is the largest material input in a garment, and a tighter layout uses less of it. The saving is real and so is the twist that follows, which is why off grain fabric turns up more often where cloth is being used sparingly.
Knits have their own version with a different cause. A jersey shirt knitted in the round comes off the machine as a tube, and the yarn in it is usually a single with twist energy still in it. Each loop leans slightly in the direction the yarn wants to untwist, and thousands of leaning loops add up to a fabric with rotation built in.
That rotation is called torque or spirality, and washing releases it the same way it releases weave skew. It is why the side seam of a tubular knit shirt walks around the body after a few washes, while a shirt made from flat knitted panels, or from a plied and balanced yarn, stays where it was sewn.
Why Pressing Will Not Fix It
An iron works by softening fiber with heat and moisture and then cooling it in a new position. On a twisted garment that produces a convincing result for about a day. The cloth looks square, the seam looks straight, and nothing underneath has changed at all. The yarns are still sitting at the wrong angle to each other.
The next wash undoes it, because the next wash re-wets the fiber and hands the decision back to the structure. You can repeat the press indefinitely and the garment will go back every time. Permanent correction means re-cutting the pieces on true grain, which on a finished garment means taking the whole thing apart first.
Spotting it before buying is far easier. A plaid or a horizontal stripe is a free grain line. Hold the garment by the shoulders and look at whether the pattern runs level across the front and whether it matches at the side seams. If the stripe runs downhill, the cloth is off square and no amount of care will keep it straight.
On a plain cloth, look at the seams instead. Hang the garment up and see whether the side seams fall vertically, whether the hem is level and whether a sleeve hangs with a turn of its own. On a knit shirt, lay it flat and check that both side seams sit the same distance from the center at the hem and at the armhole.
Off Grain Fabric In Oak Lawn
Oak Lawn laundry rooms see a lot of heavy cotton at this time of year. Flannel pants, plaid shirts, twill and brushed cotton all come out of storage at once, and plaid is the cloth that shows skew most plainly. A shirt that looked fine on a hanger all year can reveal a crooked check the first time it is properly washed.
Cold weather also means most drying happens indoors in a machine rather than on a line, and tumbling is the step that lets a skewed cloth move. There is nothing wrong with that. It would have relaxed eventually in any case. Tumbling simply gets it over with sooner, usually in the first two or three washes rather than across a season.
Since the first wash is the one that reveals the fault, it is worth giving new cotton a cycle of its own before it is mixed in with everything else. WaveMAX Oak Lawn, at 6345 W 95th St, has a range of machine sizes, so a separate load of new shirts or pants does not have to mean a half empty drum.
Machines For A Separate Load
New cotton behaves differently from cotton that has already settled, so it earns a cycle of its own. A range of drum sizes makes that practical, because a small load does not need a large machine and a bulky one does not need to be split in two. Either way the cloth has room to move and relax evenly.
The machines at our self-service laundry on West 95th Street come in enough sizes that a first wash of new shirts or pants can be run on its own, with room in the drum for the cloth to work itself square instead of being held in a packed ball.
Our machines and the store are cleaned daily.
Our wash-dry-fold service covers the everyday laundry.
For general guidance, The American Cleaning Institute publishes a fabric care guide that is a useful cross-check.
The short version
Grain means the warp and the weft crossing at a true right angle. Finishing can pull cloth out of square, and heat setting can hide that until water softens the fiber and lets the weave relax back toward square. Pieces cut from skewed cloth then rotate, which is the spiraling side seam and the hem that will not sit level. Pressing is temporary. The tell before buying is a plaid or a stripe that runs downhill.
WaveMAX Oak Lawn is at 6345 W 95th St, easy to reach from Oak Lawn and the surrounding area. If you have a load that will not fit at home, call us at 708-529-0286.