The array method provides objective measurements for determining the fiber length and length distribution in a sample of cotton. The results can be plotted to show the length-weight distribution of all the fibers in the sample. Data obtained from array tests are useful in fiber length research studies, for investigation of changes in fiber length distribution in ginning and mill processing, and for other research purposes.

Upper quartile length is correlated with, but usually longer than, Fibrograph and 2.5 % span length as defined in Test Method D1447. Judgment must be used in making comparisons between length measures from arrays and measures obtained by other methods, which may be basically different.

The coefficient of length variation is a measure of length distribution, or nonuniformity of length. Because the fiber weight-length distribution is usually highly skewed, statistical judgments based on the assumption of normality are not justified.

The array method makes a physical separation of fibers of different lengths. It therefore serves as a standard, or benchmark, with which other methods may be compared and by which their precision and accuracy may be judged.

Test Method D1440 for testing length and length distribution of cotton fibers (array method) is not commonly used for acceptance testing of commercial shipments.

a and cBanks of combs.

bForceps, tips padded with hard leather, for transferring fibers from one set of combs to the other.

dDepressor for placing fibers in combs.

fDissecting needle.

gFork for scooping up fiber groups off velvet surface.

hAluminum plate covered with velvet cloth.

iSpecial rule for measuring length of fiber groups.

kSmooth plate for placing fibers onto velvet surfaces.

lWire rack for holding fiber groups wrapped in papers.

mSmooth pointed tweezers.

nLift for raising combs in place.

oRack for holding velvet-covered boards.

pVelvet-covered boards on which several pulls have been arrayed.

Note-Other accessories required for length arraying, not shown above, consist of the following: small whisk broom for cleaning velvet surfaces, one pair of tweezers with smooth round tips, forceps similar to b but having tips padded with rubber for laying groups on velvet surfaces, small papers for wrapping groups of fibers (papers 2½ by 3 in. (62 by 75 mm)) with small envelopes for them (2½ by 4¼ in. (62 by 110 mm)), and balances having ranges from 0 to 25 mg and 0 to 100 mg.

FIG. 1 Combs and Accessories for Arraying Fibers According to Length