29 October 2004

Science and cotton

Forrest M. Mims III

So far laboratory chemists have not managed to duplicate all of the most desirable properties of cotton and certain other natural fibers. Meanwhile, agricultural scientists have continued to make advances in the cultivation of cotton.

Today cotton harvesting and processing is highly automated. After the leaves of the plants are chemically defoliated, harvesting machines roll through the fields to collect the harvest.

Prior to the Civil War, most of the cotton harvest in the United States was the work of slaves. Old timers still recall when people harvested cotton by hand across the South.

Recently 83-year old Ermenia Ortega told me what it was like to pick cotton in the hot fields of New Mexico and Texas. The pickers wore gloves with the fingers removed to protect their hands from the sharp bolls.

They dragged a long sack between the rows until it was filled with around 45 kg (about 100 lbs) of cotton. There was no day care in those days. Toddlers rode on the sacks until they became too full. Then they followed on foot.

Mrs. Ortega said she picked 225 kg (about 500 lbs) on some days. That’s the equivalent of a full bale.

Cotton harvesting machines began arriving on the scene in the 1940s, 150 years after Eli Whitney’s cotton gin revolutionized cotton farming.

Prior to the cotton gin, seeds had to be removed from cotton by hand. Whitney’s invention mechanically separated seeds from the cotton. In one day a cotton gin could clean 23 kg (about 50 lbs) of cotton.

Today’s modern cotton gins can clean, remove the seeds, sort and compress 6,800 kg (15,000 lbs) of cotton in only an hour!

Chemists have spent lifetimes trying to invent synthetic fibers with the properties of cotton. They have succeeded in producing colorfast, wrinkle free fibers. But they have yet to duplicate the comfort of cotton clothing on a hot summer day.

Besides clothing, cotton is used to produce thread, string, yarn and light rope. Rugs and carpets are made from cotton, as are fine papers and even some explosives. The seeds separated from the cotton during the ginning process are a valuable source of oil.

Texas produces more cotton than any other state. So much is harvested in some areas that the rural roads are lined with cotton that blows from the trailers and fields during the harvest season.

Forrest M. Mims III and his science are featured online at http://www.forrestmims.org/.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.