Flannel may be brushed to create extra softness or remain unbrushed. Brushing is a mechanical process wherein a fine metal brush rubs the fabric to raise fine fibres from the loosely spun yarns to form a nap on one or both sides. If the flannel is not napped, it gains its softness through the loosely spun yarn in its woven form.
Flannel is commonly used to make tartan clothing, blankets, bed sheets, and sleepwear. The term "flannel shirt" is often mistakenly used to refer to any shirt with a plaid or tartan pattern casually. However, it is actually just a form of fabric and there can be flannel shirts that are not plaid.
The origin of the word is uncertain, but a Welsh origin has been suggested as fabric similar to flannel can be traced back to Wales, where it was well known as early as the 16th century. The French term flanelle was used in the late 17th century, and the German Flanell was used in the early 18th century.
Flannel has been made since the 17th century, gradually replacing the older Welsh plains, some of which were finished as "cottons" or friezes, which was the local textile product. In the 19th century, flannel was made particularly in towns such as Newtown, Montgomeryshire, Hay on Wye, and Llanidloes. The expansion of its production is closely associated with the spread of carding mills, which prepared the wool for spinning, this being the first aspect of the production of woollen cloth to be mechanised (apart from fulling). The marketing of these Welsh woollen clothes was largely controlled by the Drapers Company of Shrewsbury.
At one time Welsh, Yorkshire, Lancashire and Irish flannels differed slightly in character due largely to the grade of raw wool used in the several localities, some being softer and finer than others. While nowadays, the colour of flannel is determined by dyes, originally this was achieved through mixing white, blue, brown and black wools in varying proportions. Lighter shades were achieved by bleaching with sulphur dioxide.
Originally it was made of fine, short staple wool, but by the 20th century mixtures of silk and cotton had become common. It was at this time that flannel trousers became popular in sports, especially cricket, in which it was used extensively until the late 1970s.
The use of flannel plaid shirts was at peak in the 1990s with popular grunge bands like Nirvana and Pearl Jam using them as one of the trademarks of their shaggy look. However, few of the mass-produced plaid shirts available at the time were actually made out of flannel. The association between flannel and plaid has led to the use of flannel as a synonym for plaid.
Flannelette typically refers to a napped cotton fabric imitating the texture of flannel. The weft is generally coarser than the warp. The flannel-like appearance is created by creating a nap from the weft; scratching it and raising it up. Flannelette can either have long or short nap, and can be napped on one or two sides. It comes in many colours, both solid and patterned.
Flannel, flannelette, and cotton flannel can be woven in either a twill weave or plain weave. The weave is often hidden by napping on one or both sides. After weaving, it is napped once, then bleached, dyed, or otherwise treated, and then napped a second time.