The classification system for upland cotton consists of instrument measurements and classer determinations. All instrument measurements currently utilized in USDA upland cotton classification are from Uster High Volume Instrument (HVI) systems and include color grade, fiber length, micronaire, strength, length uniformity index, color Rd, color +b, and trash percent area. Classer determinations are leaf grade, extraneous matter and preparation.

Classification of all cotton samples are based on official standards as determined by the United States Department of Agriculture (USDA). Quality Control is a vital part of the USDA classification system and HVI instruments are routinely tested for accuracy based on maximum allowable tolerances. Both temperature and humidity conditions influence the measurement of cotton fiber properties, and are therefore tightly controlled in the classing laboratory.

Fiber Measurements: A description of each measurement included in USDA's official cotton grade follows:

Color - Color measurements are made by a colorimeter. The instrument measures grayness (Rd), which indicates how light or dark the sample is, and also yellowness (+b), which indicates how much yellow color is in the sample. The color grade is determined by location the point at which the Rd and +b values intersect on the Nickerson-Hunter diagram for upland cotton. The majority of the crop is classed as white 21, 31, or 41 color grade. A 32 or 42 would be a light spotted grade. There are 25 official color grades plus 5 categories of below-grade color. Color gives an indication of the fibers' ability to accept dyes in the manufacturing process.

Fiber Length - Fiber length is measured on a beard of cotton fibers on HVI systems and is reported in hundredths of an inch and equivalent staple length in thirty-seconds of an inch. Length is a good indicator of yarn strength and spinning efficiency.

Micronaire - The airflow instrument in the HVI system measures resistance to air flow which is related to fiber fineness. Fineness and maturity are highly correlated within the same cotton variety. Fiber fineness affects yarn appearance, yarn uniformity, and yarn strength.

Strength - The fiber strength measurement is made by clamping and breaking the beard of fibers with 1/8-inch gage spacing between the clamp jaws. The strength reported is the force in grams required to break a bundle of fibers one tex unit in size. A tex unit is equal to the weight in grams of 1,000 meters of fiber. Fiber strength is closely related to yarn and fabric strength and to spinning efficiency.

Length Uniformity - Length uniformity measures the degree of fiber length uniformity in a sample. Fiber length uniformity is related to spinning efficiency, yarn uniformity, and yarn strength.

Trash percent area- The trash measurement is made by a video trash meter, which measures the percentage area of trash on the sample surface. This measurement provides an estimate of the total amount of trash in the bale.

Leaf Grade - Highly trained human classers determine the leaf grade by comparison with the practical forms of the Universal standards for the grades.

Extraneous Matter – Extraneous matter is any substance in the cotton other than fiber of leaf. Examples of extraneous matter are bark, grass, preparation, seed coat fragments, dust and oil. The kin of extraneous matter, and an indication of the amount, light or heavy, are noted by the classer on the classification document.

Preparation - Classers determine the degree of smoothness or roughness of the ginned cotton lint termed preparation or prep or sometimes referred to as spindle twist. Various methods of harvesting, handling, and ginning cotton produce differences in roughness or smoothness of preparation that sometimes are very apparent. If cotton has abnormal preparation, that notation is shown under Extraneous Matter on the classification record.

Classing Offices - USDA operates 12 cotton classing facilities across the cotton belt. The facilities are designed specifically for cotton classification and are staffed exclusively with USDA personnel. Cottons grown in Arkansas are classed in three different classing offices depending on the county, which include Rayville, LA, Dumas, AR and Memphis, TN. Additional information of cotton classification can be obtained from the web at: http://www.ams.usda.gov/Cotton/