Updated May 19, 2020.
Cotton is the most widely used plant fiber.It’s believed to have been used to make cloth since prehistoric times and the oldest fragment of cotton cloth dates from about 5000 BC.
Although cotton was known to people north of the Mediteranean, its origin was a mystery. Herodotus wrote that it came from a tree in India. The modern word for cotton in several languages, baumwolle, hearkens back to this story, meaning, literally, ‘tree wool.’
How Cotton Is Made
Cotton fiber is the bolls, a soft fluffy protective covering around the cotton seed. The plant, a shrub, grows in sub-tropical and tropical climates. That’s why some of the best cotton comes from the coastal islands of Georgia or from Eygpt.
The cotton is picked and the seeds are separated from the bolls using a cotton gin. Its invention revolutionized cotton production and led directly to the fiber’s popularity.
Once harvested and separated, the fibers are combed to straighten them, the spun into threads of various thicknesses. Cotton is classified by the length of its fibers, called staples. The finest kinds of cotton are also named, such as Egyptian or Pima cottons.
Characteristics of Cotton
Cotton thread absorbs dye easily, making it available in a wide range of colors. Naturally it has a bit of light in it, called lustre. This can be enhanced (pearl cotton) or diminished (flower thread) depending on how the thread is treated.
Cotton is also an inelastic fiber. This means that it can’t return to it original shape when stretched. For embroidery, this means that cotton threads will not fluff up to fill the space around them.
It can deteriorate in sunlight but is resistant to moths but not silverfish. Storage of cotton in wooden or cardboard boxes can weaken the fibers (I’ve had this happen to me.)
“Mercerization” is one common treatment for cotton that makes it more lustrous. In it the chemical structure of the thread is changed, also making it softer. A final step in this process is to pass the thread over an open flame to incinerate any small stray fibers, also increasing the sheen.
Pearl cotton is a mercerized thread. Generally mercerized threads are made from longer-staple cottons.
While we think of cotton as a workaday thread, it has a long history where the need for cotton drove much important industrial development. So it’s not just an inexpensive skein of floss you hold,it’s a bit of history.