Every piece of woven fabric is made from two sets of threads: the warp, which runs the length of the cloth and is held under tension on the loom, and the weft, which passes back and forth across the width, interlacing with the warp to build up the fabric row by row. Everything that distinguishes one weave structure from another — whether plain, twill, tapestry, or something more complex — comes down to the pattern in which warp and weft pass over and under each other.
The Warp
Warp threads are the structural backbone of the cloth. They are wound onto the loom's warp beam before weaving begins, threaded through the loom's heddles and reed, and held at a specific tension. The spacing of the warp — the number of threads per centimetre — is called the sett, and it is one of the most important variables in the setup.
A sett that is too open (too few ends per centimetre) produces cloth that is loose and gap-prone; too close (too many ends per centimetre) causes the warp threads to crowd together so that the weft cannot pass through freely. Finding the correct sett for a given yarn requires knowing the yarn's grist (weight per unit length) and adjusting for the intended weave structure. The wraps-per-centimetre method is a reliable starting point: wrap the yarn around a ruler for one centimetre without gaps, count the wraps, then divide by two for plain weave or adjust for other structures.
Warp yarn is typically stronger and more tightly spun than weft yarn, because it must withstand the continuous tension and the abrasion of the reed and heddles moving against it during weaving. Linen, tightly spun cotton, and plied wool are often used as warp; loosely spun singles, fragile fibres, or specialty yarns better suited to weft positions.
The Weft
The weft is the yarn that forms the fill of the cloth. A shuttle — a flat or boat-shaped tool holding a bobbin or wound yarn — carries the weft through the shed (the opening formed between raised and lowered warp threads) in a single pass. After each pass, a beater or reed is drawn toward the weaver to press the weft into position against the previous row. The force applied at this stage affects the cloth's density and drape.
Weft can be any yarn that will pass smoothly through the shed. In balanced weaves, the weft and warp are the same yarn at the same sett, producing a cloth in which both sets of thread are equally visible. In weft-faced weaves — common in tapestry and rug weaving — the sett is open enough that the weft covers the warp entirely. In warp-faced structures, the opposite is true.
Plain Weave and Tabby
Plain weave (also called tabby) is the simplest interlacement: every warp thread alternates over one weft, under the next, in a repeating sequence. The draft notation for plain weave on a four-shaft loom reads as shafts 1 and 3 rising for one pick, shafts 2 and 4 rising for the next.
Plain weave produces a stable, durable cloth — the maximum possible interlacement between warp and weft in a balanced weave. It is the structure most commonly used for dish towels, lightweight scarves, and fabric intended for printing or embroidery because the flat, even surface does not compete visually with applied surface treatments.
A variant of plain weave, called rep weave, uses alternating thick and thin warp threads to create a ribbed surface texture without changing the basic over-one-under-one interlacement.
Twill
Twill produces the diagonal lines visible in denim, herringbone fabric, and many suiting cloths. The interlacement shifts by one thread on each successive row — each weft thread steps over or under the warp threads by one position compared to the row before it. This stepping creates a diagonal line called the twill line, and the steepness of that line depends on the number of shafts involved and the threading sequence.
A 2/2 twill means each weft thread passes over two warp threads, then under two — the most common form, used for fabric with good drape and a characteristic surface texture. A 3/1 twill is warp-dominant (the warp floats more) and produces a harder-wearing surface, typical in denim. Herringbone reverses the twill direction at regular intervals, creating the V-shaped zigzag pattern that is recognizable in traditional Canadian blankets and outdoor garments.
Twill requires at least four shafts on a floor loom, making it inaccessible on frame looms and possible but limited on rigid heddle looms (through pick-up stick methods that approximate a twill effect without true shaft rotation).
Sett, Beat, and the Relationship Between Structure and Drape
Two cloths woven from identical yarns at identical setts but with different weave structures will behave differently in hand and drape. Twill produces softer, more drapey cloth than plain weave at equivalent sett, because the longer floats (threads crossing over more than one thread at a time) allow the cloth to flex more easily. Satin weave, with the longest floats of the common structures, produces the most fluid cloth — at the cost of durability, since long floats are more susceptible to abrasion and snagging.
Beat affects density and therefore both weight and drape. A firm beat compacts the rows closer together, producing denser, heavier cloth. A light beat — used deliberately for lace weaves and open structures — produces airy fabric. Beat consistency is one of the skills that takes longest to develop; an inconsistent beat produces a cloth that varies in density in a way visible after wet finishing.
Wet Finishing and Its Effect on Structure
Cloth taken off the loom is called "loom state." For most fibres, especially wool and cotton, wet finishing changes the cloth considerably. Wool blooms and the weave structure tightens as the fibres expand; cotton softens and shrinks somewhat. The structure you weave must account for the finishing: a sett appropriate for loom-state cotton may be slightly too open for the finished cloth if the finishing wash is not factored in.
For weavers working in Canada, the Ontario Handweavers and Spinners website maintains a list of regional study groups where finishing methods and sett experimentation are common topics. Local guild workshops provide hands-on experience with finishing that is difficult to replicate from written descriptions alone.