Cotton Plant Classification

• These cotton blossoms are classified by measuring quality factors. Comstock Images/Comstock/Getty Images

  The cotton (Gossypium hirsutum L.) plant classification for cotton fiber quality are officially measured by the United State Department of Agriculture. The measurements are done in laboratories using high-volume precision instruments. Since atmospheric conditions influence the measurement of cotton fiber properties, the temperature is maintained at 70 degrees F. and relative humidity at 65 percent.

Fiber Length

• Fiber length is measured by passing a beard of parallel fibers through a sensing point on the instrument. The beard is clasped by a clamp, combed and brushed to get the parallel fibers. Fiber length affects yarn strength, evenness and fineness of yarn produced. Strong classification is 1.08 inches, and weak classification is 0.79 inches or less.

Length Uniformity

• In a bale of fibers, length uniformity is the percentage of mean length and upper half mean length of the fibers. There is natural variation in the length of cotton fibers. If the degree of uniformity is very high, then the percentage would be 85 percent or higher. A very low classification is 77 percent or under. Length uniformity has affect on yarn evenness, strength and the spinning process.

Fiber Strength

• Fiber strength is measured by grams of tex, which is a unit equal to the weight in grams of 1,000 meters of fiber. The strength that the instrument reports is the force it takes to break a bundle of fibers that are one tex unit is size. The classification is very strong if it is 31 g or above, and weak if it is 23 g or below.

Micronaire

• Fiber fineness and maturity is called miconaire. It is measured by air permeability of a constant mass of cotton fibers that are compressed to a fixed volume. The instrument used for the measurement is an airflow unit. If cotton fiber has a micronaire measurement of 3.7 to 4.2, then it is considered high quality. If it has a micronaire measurement of 3.5 or less, then it is considered low quality. Fiber fineness affects processing performance and the product quality.

Color

• The cotton fiber color is determined by degree of reflectance and yellowness. The color of the fiber will affects its ability to hold dyes and finishes. The color is graded based on a comparison on a chart established by the USDA American Pima Standards.