28 August 2026 · 6 min
The seamless tile is not the sett
Write down a tartan and you write down a sett: the run of threads, in order, that the pattern is made of. It is tempting to think the cloth therefore repeats every sett. It does not, and the gap between those two numbers is where most plaid generators quietly fail.
Two numbers, not one
Take K4 B24 K2 W6, mirrored on the first and last stripe. That expands to
62 threads. Now weave it as a 2/2 twill, which repeats every 4 ends.
The colour repeats every 62 threads. The interlacement repeats every 4. The cloth only repeats where both line up — the lowest common multiple:
lcm(62, 4) = 124
So the seamless tile is 124 threads, not 62. Twice the sett. Cut it at 62 and every seam lands mid-twill.
What that actually looks like
Both figures below are the same cloth, drawn by the engine that runs the designer. The first is tiled at the sett length; the second at the true repeat. Follow the white diagonal across the joins.
On a screen at small scale the fault hides. Printed at yardage, or laid out across a garment, it reads as a stutter every 62 threads — the kind of thing a mill sends back.
Why it gets missed
Because it only appears when a tool models the weave at all. Fill each stripe with flat colour and there is no diagonal to break: the sett is the tile, and the arithmetic never comes up. It is drawing the interlacement thread by thread that creates the problem — and makes it visible.
The number is also easy to hide. Most generators show you a swatch, not a tile size, so nothing on screen ever says 124.
Two ways out
You can accept the larger tile. Nothing is wrong with a repeat of 124; it is simply bigger than you might have expected, and worth knowing before you send a file.
Or you can make the sett fit. Add two threads to the last stripe and the warp runs to 64, which divides by 4, and the tile collapses to 64 — one sett, one repeat. At 26 ends per inch those two threads add 2.0 mm to the width of the repeat. That is why the designer offers to add them rather than just reporting the number.