III. Classification of American Pima Cotton

Classification procedures for American Pima cotton are similar to those for American Upland cotton, including the use of HVI measurements. The most significant difference is that the American Upland color grade is determined by instrument measurement, while the American Pima color grade is still determined by highly-trained cotton classers. Different grade standards are used because the color of American Pima cotton is a deeper yellow than that of Upland (see exhibit B, American Pima colorimeter diagram). Also, the ginning process for American Pima cotton (roller ginned) is not the same as for Upland (saw ginned). The roller gin process results in an appearance that is not as smooth as that obtained with the saw ginned process.

There are six official grades (grades "1" through "6") for American Pima color and six for leaf. All are represented by physical standards. There is a descriptive standard for cotton which is below grade for color or leaf. A different chart is used to convert American Pima fiber length from 100ths to 32nds of an inch. This chart is below.

IV. Reliability of Classification Data

The reproducibility of classing results from one USDA facility to another is the measure used by USDA to determine the reliability of the data it produces. Laboratory–to–laboratory reproducibility is more difficult to achieve than within–lab or same–machine reproducibility, because it is more difficult to maintain identical testing conditions. A comparison of laboratory–to–laboratory results provides a more realistic assessment of the degree of reproducibility than can be expected in the manufacturer's laboratory after shipment to the textile mill. The tabulation below reflects USDA lab–to–lab reproducibility as of 2000. These results are based on more than 100,000 checklot samples, randomly selected, daily, from the production of each instrument line and each classer at each USDA classing facility throughout the 2000 season and retested at the agency's Quality Assurance unit in Memphis.