Why the edge of a tank top does not fray
Short answer: Knitted fabric is made of loops, not of crossing threads. When it is cut, the loops do not fall apart the way woven fabric does, and the edge simply rolls. That is one reason some tops can have a completely raw edge.
Woven fabric frays, knit does not
In woven fabric the threads hold each other only by crossing. If they are cut, they slide out. In knit, each loop holds on to its neighbour above and below. That is why you can cut knitted fabric without it starting at once to unravel along the cut.
Why the edge can stay raw
A cut knit edge can be left without a seam, and it simply rolls into a thin cord. This is used in light tops to avoid a thick edge. It gives a simple, light finish that lies flat against the body and does not add bulk under other clothes. See bamboo jogging suit for women.
When it goes wrong anyway
If a stitch breaks at the edge, a ladder can run. That is why most edges are sewn anyway, especially on garments that stretch a lot. A seam holds the edge together and spreads the strain. See bamboo sweatwear and bamboo tops for women.
Why the edge rolls
Knitted jersey has a smooth side and a reverse side, and they pull in different directions when the edge is free. The result is that the edge rolls towards the reverse and forms a thin roll. It is a natural property of the fabric and not a fault in the seam or the garment.
A top without a thick seam
Without a thick seam the edge is thin and soft against the skin. That suits tops worn close to the body or under a jacket. A seam can leave a visible line under close-fitting clothes, and you avoid that line when the edge is left raw, as long as the fabric suits it.
How to check the edge
Look at the edge at the bottom of the top. If it has rolled evenly without broken stitches, it is fine. If you see a stitch that has gone, or a small ladder, take care with it. Do not pull the edge, and avoid hanging the garment on lines, where the edge can be stretched crooked.
Can I change the edge myself
Yes. You can cut a knitted top a little shorter, and the edge rolls at its new place. Cut evenly and in a straight line, so the roll is the same all the way round. For a sturdier finish you can sew the edge with a narrow zigzag stitch that follows the stretch of the fabric.
Wear over time
A raw edge wears slowly with washing and use. It can become a little uneven, but it does not come apart as a woven edge would. If you treat the fabric gently, wash carefully and avoid high heat, the edge keeps its round shape for longer. Slight wear at the edge is normal for knit.
Choose by how you use it
Think about how you will use the top. If it is to fit closely and stretch a lot, a sewn edge is the sturdiest. If it is to be light and flat under other clothes, a raw edge is a good solution. Look at how the edge is made and choose what suits the day.
Frequently asked questions
Can I cut a knitted garment shorter myself
Yes. The edge rolls but does not fray. Sew it with a narrow zigzag if you want a sturdier finish that moves with the fabric when you stretch it.
Why does denim fray so much
Because woven fabric is made of straight threads that can slide apart. When they are cut, they lose hold of each other, and the edge unravels if it is not sewn.
Can knit fray over time
The edge can become uneven from wear, but it does not come apart like woven fabric. Gentle washing and low heat help the edge keep its shape for as long as possible.
See our range of bamboo tank tops for men.
