Woven and knit fabric
How the two main fabric structures differ in feel, stretch, comfort in the heat and cover from the sun.
Woven fabric is made by interlacing two sets of yarn at right angles, while knit fabric is made by forming a continuous yarn into interlocking loops. A classic button-front shirt is usually woven, and a T-shirt is usually knitted. The two structures behave differently, from how much they stretch to how well they keep out the sun.
How are woven and knit fabrics made?
Weaving crosses lengthwise threads, called the warp, with crosswise threads, called the weft. According to Encyclopaedia Britannica, weaving is the major method of fabric production, and its three basic weaves are plain, twill and satin. Knitting works differently. It builds fabric from columns and rows of loops, and commercial knits are generally made by machine. Because each loop depends on the one beside it, some knits can run when a single loop breaks.
Which stretches more, woven or knit?
Knit fabric stretches more. Britannica notes that knits can generally be stretched further than woven types, and that the common weft knits give most across their width. In a woven cloth, the yarns are held in place by friction where they cross, so the fabric gives far less. In practice, a woven shirt tends to keep a cleaner line and a crisper collar, while a knit moves with you and feels softer against the skin.
Which is cooler in hot weather?
Neither is cooler by default. How a fabric feels in the heat depends mostly on its fibre, its weight and how tightly it is made, not only on whether it is woven or knitted. A fine, light weave and a light, open knit can both feel airy, while a dense weave or a heavy knit will feel warm. Fit matters as well, because a garment with some room lets air move between the fabric and your skin. For more on this, read how to dress for humid heat.
Do woven or knit fabrics block more sun?
Density matters most, but stretch works against knits. ARPANSA explains that the tighter the weave, the less space there is for UV to pass through, and that thicker fabric gives higher measured protection. It adds that construction decides whether the open area of a fabric changes under tension: stretching a knitted fabric normally lowers its UPF rating as the spaces open up. The Skin Cancer Foundation makes the same point about tight clothing, which can stretch and offer less protection as the fibres pull away from each other. The fibre plays a part too; see nylon for one common shirt fibre.