Pull a t-shirt out of the machine and the hem has rolled under itself, tight as a pencil. The sleeve openings have done the same thing. Nothing is torn, nothing has shrunk, and yet the shirt looks slept in before anyone has worn it. This is not bad sewing and it is not something the wash got wrong. It is the fabric doing exactly what its own structure tells it to do, and it will do it again every time the shirt is cleaned. Once you know where that pull comes from, the drying stage stops being guesswork and starts being a decision.
How a knit is actually built
A woven fabric is two sets of straight yarns crossing at right angles, locked by friction where they pass over and under each other. A knit is one continuous yarn pulled through itself in a chain of loops. That single difference explains almost everything a knit does. The loops can lean, stretch and swap tension between neighbors, because nothing in the structure is holding a straight line.
Each loop has a rounded head and two legs that run down into the loop below. On the face of the fabric you see the legs, which read as neat vertical columns. On the back you see the heads, which read as horizontal ridges. The yarn is bent hard at every one of those turns, and bent yarn carries stored tension. It would rather straighten than stay curved, and it spends the life of the garment trying.
Single jersey knit, the fabric most t-shirts are made from, puts all its legs on one side and all its heads on the other. It is lopsided by design, and that lopsidedness is what gives it the smooth face and soft drape people buy it for. Rib and interlock fabrics alternate the two faces, so the stored tension cancels out. Cuffs and collars are usually rib for exactly that reason.
There is one more thing locked in at the knitting stage. Yarn is spun with twist, and twist has a direction. As the loops form, that twist tries to unwind and pushes the columns of stitches very slightly off vertical. In a plain tube-knit shirt you can see the side seam wandering around the body after a few washes. The fabric is not moving. It is relaxing into the shape it was always under tension to hold.
Why a cut edge rolls under
Inside the body of the fabric, every loop is held by the loops around it. The stored tension has nowhere to go. Cut across that fabric and the loops along the cut lose half their support at once. Nothing is left to balance the bend in the yarn, so the edge does the only thing it can and folds toward the side with more bulk.
Which way it folds depends on which edge you are looking at. A horizontal edge, such as the bottom of a shirt, rolls toward the back. A vertical edge, such as the raw side of a scarf, rolls toward the front. That is why a raw-edge shirt hem tucks neatly under itself while a raw-edge strip of the same cloth turns into a tube going the other way. Same fabric, different direction of stored bend.
Hems, bands and bindings exist to cancel that pull. A folded and stitched hem doubles the fabric and puts two opposing faces against each other, so neither one wins. A rib neckband does the same job with a balanced structure. When a hem is stitched too tightly, or when the thread breaks and the fold releases, the curl comes straight back because the fabric underneath never stopped wanting to roll.
Some garments leave the edge raw on purpose. A rolled sleeve opening on a summer top is a design choice, and fighting it is wasted effort. The test is whether the roll is even. An even roll all the way around is the fabric behaving normally. A roll that is tight in one place and loose in another usually means the edge was stretched while it was wet.
What water and heat do to loops
Cotton swells when it takes on water, and it swells across its width far more than along its length. Every fiber in every yarn gets fatter. The loops, which were already crowded, now have less room, and the whole fabric shifts to make space. This is why a knit feels heavier and looser wet, and why the edge curl tightens the moment the load comes out of the drum.
Agitation gives the loops permission to move. Wet fiber is softer and slides more easily, and the tumbling action works the fabric back and forth thousands of times. Stored tension that had been sitting quietly gets released in small increments. A shirt that curled a little when new curls more after a season of washing, and that is the reason why. Nothing has gone wrong. The fabric has simply been allowed to finish relaxing.
Heat is what makes a shape permanent. Cotton loses and regains its hydrogen bonds as it wets and dries, so whatever position it is holding when the last of the water leaves is the position it sets into. Polyester goes further. It softens at drying temperatures and hardens again on cooling, which means a fold pressed in by a hot drum can be genuinely difficult to remove later.
The practical consequence is that the cool-down at the end of a dry cycle matters as much as the heat at the start. Fabric coming out warm is still soft and still movable. Fabric that has cooled in a heap has already set in that heap. The window for straightening an edge closes as the load cools, not as it dries.
Drying decides how the edge sits
The useful habit is to catch the garment while it is still slightly damp. Lay it face down, run a thumb and finger along the hem to unroll it, and press it once against the surface so the fold lies open. Then leave it. The remaining water carries the fiber into that position as it evaporates, and the edge dries where you put it rather than where it fell.
Hanging a soaking knit by the shoulders is the common mistake. Wet cotton can hold most of its own weight again in water, and all of that hangs from two narrow points. The body stretches downward, the shoulders pull into points, and the hem tightens its roll because the fabric above it has gone long and narrow. A drying rack that supports the whole garment avoids the whole problem.
In a tumble dryer, lower heat and a shorter run beat high heat every time, because the fabric spends less of its drying at a temperature that can set a bad fold. A load that has room to move also helps. Packed tight, shirts dry in whatever shape they are jammed into, and the hems finish hard and uneven.
Pressing and storing knitted tops
If an edge has already set badly, steam is the tool that undoes it. Steam re-wets the fiber just enough to release the bonds holding the fold, and a warm iron pressed straight down, not dragged, lets the hem relax open. Dragging an iron across a knit stretches the loops sideways and creates a wavy edge that is harder to fix than the curl was.
Press from the reverse side where you can. The face of a jersey knit takes on a shine from direct contact with a hot plate, because the smooth leg side reflects light evenly and flattened fiber reflects it differently. Working from the back keeps the face matte. A pressing cloth does the same job if the garment cannot be turned.
As the season turns and lighter tops start going underneath sweaters and jackets, the hems matter again for a different reason. A rolled hem under a layer reads as a lump, not as a detail. Getting the edges to lie clean before the busier stretch ahead means the shirts you reach for are ready, and the pile of things needing a press stays small.
Knitwear Washing in Chandler
Chandler runs dry for much of the year, and dry air changes how knits behave. Moisture leaves the fabric faster than most people expect, so the window in which a hem can still be smoothed open is shorter than it would be somewhere humid. Checking the load a little earlier is usually all it takes.
Dry heat also means fine dust settles on everything, including clothes drying indoors. Dust sitting on a damp knit works into the loops and dulls the color over time. A closed drum keeps that off the fabric while it dries, which is one reason a lot of people here prefer a machine dry to an open rack for anything dark.
Households in Chandler also tend to run larger loads of light cotton than heavy winter fabrics, which suits knits well as long as the drum is not packed. Knits need space to tumble loose. Give them that and the edges come out even, which is most of the work done before anything touches an iron.
Room for the Knits
Most curled hems come down to a drum that was too full and a load left to cool in a pile. Both are easier to avoid on a machine with real capacity. Larger drums let a shirt open out and turn instead of pressing against the glass, and separate dryers let you drop the heat rather than push a full load through on high.
The machines at our self-service laundry on North Arizona Avenue are sized so a full basket of shirts still has room to turn, and the dryers run cool enough to finish a knit without setting a fold you then have to steam out at home.
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
A curled hem is the fabric’s structure showing, not a fault. Single knits are built lopsided, so any cut edge rolls toward the side with more bulk. Water loosens the loops, heat sets whatever shape they are in, and cooling locks it. Catch the garment while it is still warm or slightly damp, smooth the edge open, and let it finish drying in that position.
WaveMAX Chandler is at 2081 N Arizona Ave 129, easy to reach from Chandler and the surrounding area. If you have a load that will not fit at home, call us at 602-603-5638.