Fibre to Form
Before the fabric comes the fibre, and these are spun or twisted into yarns. Twisting helps to bind the fibres together and make them stronger.
There are two twist directions, termed 'S' and 'Z' twist. S-twist yarns are spun clockwise, and Z-twist are spun anti-clockwise. But the easiest way to determine which one is which is to visualise the letters 'S' and 'Z' as shown in the diagram.
Woven and knitted fabrics will often require a stronger yarn than a single twist yarn to construct a durable fabric. This is where 'plying' the yarn becomes necessary. Plying is the twisting together of two or more 'S' and 'Z' twist yarns. The individual yarns must be twisted in the same direction before being plyed/twisted in the opposite direction. For example, two or more S-twist yarns are plyed together in a Z-twist direction or vice versa before being woven or knitted into a fabric. Plying in the opposite direction of the twist balances out the yarn to avoid over twisting and knotting.