Understanding pattern structure in woven tartan fabric
A sett is the specification for a tartan pattern expressed as a sequence of colour codes and thread counts. It describes, in order, which colours are used and how many threads of each colour appear in one complete sequence of the pattern. For example, a simple sett might specify: green for 32 threads, blue for 8 threads, black for 4 threads, blue for 8 threads, green for 32 threads, and so on. This sequence defines a single repeat of the horizontal and vertical structure of the tartan, which is then woven identically in both the warp (vertical) and weft (horizontal) directions to create the characteristic grid and diagonal effects visible in the finished cloth.
The colours in a sett are not arbitrary choices made after the fact. They are encoded into the warp threads before weaving begins, determining the entire visual structure of the fabric. Because the same sequence runs in both directions of the weave, the intersecting colours produce a range of visual effects beyond the individual thread colours — secondary squares appear where two colours cross, diagonal lines emerge from the regular repetition, and the overall impression of the tartan's characteristic complexity comes entirely from this simple underlying specification.
When a tartan is registered with the Scottish Register of Tartans, the sett is the primary technical document submitted. It allows any competent weaver anywhere in the world to reproduce the same design if they follow the specification. This is why authentic clan tartans woven in Scotland and commercially produced tartans made elsewhere can be visually identical — they are following the same registered sett, even though they may differ significantly in yarn quality, weight, and finish.
A tartan sett is a repeating unit — the same sequence of thread colours and counts tiles across the full width and length of the woven cloth. Most tartan setts use a reflective or pivot repeat, which means the sequence runs forward to its midpoint and then mirrors back to the beginning before starting over. This reflective structure is what creates the symmetrical, balanced appearance of most traditional tartans. The pivot points — the colours at each end of the sequence — appear at both the boundary between repeats and at the internal reflection point, and these pivots are often the most visually prominent stripes in the finished pattern.
The physical size of one sett repeat on the finished cloth depends on the total thread count specified in the sett and the density of the weave. A sett with 200 threads total in its repeat will produce a larger physical pattern than a sett with 80 threads total, even if both use the same colours in similar proportions. This is because more threads means more distance is needed to complete one full sequence before the repeat begins again. The practical consequence is that tartan patterns vary considerably in the physical size of their repeat, from compact designs where a full repeat might measure only an inch or two, to complex patterns where a complete sett repeat spans four or more inches of fabric.
When tartan fabric is cut to make a garment, the size of the sett repeat determines how many full repetitions appear across the width of the apron, how the pattern lines up across seams, and how the design looks across the pleated back panel. A larger sett repeat means that individual colour blocks are more prominent and the overall pattern has a bolder, more open appearance. A smaller repeat creates a denser, finer visual texture where the individual colour stripes are narrower.
When a kiltmaker cuts tartan fabric to construct a garment, the sett repeat size directly affects how the pattern is positioned across each section. Skilled kiltmakers generally aim to start the apron at a consistent point in the sett repeat — typically at the central pivot of the main colour stripe — so that the pattern is centred on the front of the garment and presents symmetrically. This matching process requires sufficient fabric to allow the maker to cut from a point in the repeat that produces a visually balanced result rather than a random section of the pattern.
Seam matching is the other major practical implication of sett size. At the side seam where the apron meets the side sections, a skilled kiltmaker will attempt to align the pattern so that horizontal stripes continue across the seam without visible interruption. This is more difficult to achieve with large sett repeats because the distance between matching pattern points is greater, requiring more precise alignment and sometimes more fabric to accomplish. Many commercially produced kilts do not attempt perfect sett matching at seams due to the labour cost involved, but high-quality bespoke kilts typically do.
The pleated back panel presents a different kind of sett consideration. Because the pleats fold the fabric and then release it below the stitch line, the visual pattern at the pleat folds is determined by exactly where the kiltmaker positions each fold relative to the sett repeat. This is the structural basis for the two main pleating methods — pleating to the sett and pleating to the stripe — which represent different choices about which part of the sett repeat to align at each visible fold edge. Both approaches require understanding the sett well enough to control where the folds fall in the pattern sequence.
The designer records each colour and its thread count in the exact order they appear in one half-repeat of the pattern.
A weaver arranges the warp threads (vertical) according to the sett before any weaving begins.
The weft (horizontal) threads follow the identical sett, creating the intersecting grid structure of the tartan.
The repeat continues in both directions, producing a consistent, seamless pattern across the full width and length of the woven piece.
For wearers of tartan traditional kilts who want to understand why their garment looks the way it does, the sett is the foundational concept. The visual complexity of any tartan — its diagonal lines, its colour intersections, its symmetrical stripes — all emerge from this single specification repeated systematically across the fabric. Knowing how the sett works does not change how you wear the kilt, but it does explain why different tartans have such distinct visual characters even when made from similar colours, and why the same tartan looks different depending on its sett size and how the kiltmaker has positioned the pattern across the garment's sections.
Once the repeating structure of a sett is understood, the relationship between woven tartan and finished clothing becomes much clearer. Learning about tartan sett structure also explains why pattern placement can have such a strong visual effect.