All about flannel
Flannel is a wool fabric (though it can also be made from cashmere or cotton), featuring a soft, fluffy nap created by brushing both sides of the cloth. It is a warm and comfortable fabric, also valued for its breathability (it allows air to pass through).
It first appeared alongside the early mechanical looms in the 18th century, in Flanders and Great Britain. Originally, flannel was always speckled in color, as it was made using strands of undyed natural wool. Today, it is common to dye flannel after weaving to achieve a solid color. It can also show subtle color variations if woven with dyed yarns.
Regardless of its final color, flannel is always washed at the end of the production process to achieve its signature slightly fuzzy texture.
The fineness of the wool fiber in flannel is generally not specified.