Reports CTRM for Agricultural and Soft Commodities | Page 25
CTRM for Ags & Softs
unit in size. Strength measurements are made on the same beards of cotton that are used for measuring fiber
length. The beard is clamped in two sets of jaws, 1/8 inch apart, and the amount of force required to break the
fibers is determined. Fiber strength is largely determined by variety. However, it may be affected by plant nutrient
deficiencies and weather. Fiber strength and yarn strength are highly correlated. Also, cotton with high fiber
strength is more likely to withstand breakage during the manufacturing process.
Micronaire is a measure of fiber fineness and maturity. An airflow instrument is used to measure the air
permeability of a constant mass of cotton fibers compressed to a fixed volume. Micronaire can be influenced
during the growing period by environmental conditions such as moisture, temperature, sunlight, plant nutrients,
and extremes in plant or boll population. Fiber fineness affects processing performance and the quality of the end
product in several ways. In the opening, cleaning, and carding processes, low-micronaire or fine-fiber cottons
require slower processing speeds to prevent damage. Fiber length and strength measurements are made on the
same “beard” of cotton. Y arns made from finer fiber have more fibers per cross-section, which results in stronger
yarns. Dye absorbency and retention are affected by the maturity of the fibers; the greater the maturity, the better
the absorbency and retention.
Color grade is determined by the degree of reflectance (Rd) and yellowness (+b) as established by official
standards and measured by the high volume instrument. Reflectance indicates how bright or dull a sample is, and
yellowness indicates the degree of pigmentation. A three-digit color code is determined by locating the point at
which the Rd and +b values intersect on the color chart for American Upland cotton. The high volume instrument
grades the color of cotton. The color of cotton fibers can be affected by rainfall, freezes, insects, fungi, and
staining through contact with soil, grass, or cotton-plant leaf. Excessive moisture and temperature levels can also
affect color during storage, both before and after ginning. Color deterioration because of environmental conditions
affects the fibers’ ability to absorb and hold dyes and finishes and is likely to reduce processing efficiency.
Trash is a measure of the amount of non-lint materials in cotton, such as leaf and bark from the cotton plant. A
digital camera scans the surface of the cotton sample, and the digital image is analyzed. The percentage of the
surface area occupied by trash particles (percent area) and the number of trash particles visible (particle count)
are calculated and reported. The ratio between percent area of trash and trash particle count is a good indicator
of the average particle size in a cotton sample. For instance, a low percent area combined with a high particle
count indicates a smaller average particle size than does a high percent area with a low particle count. A high
percent area of trash results in greater textile mill processing waste and lower yarn quality. Small trash particles,
or “pepper trash,” are highly undesirable, because they are more difficult for the mill to remove from the cotton lint
than are larger trash particles.
Leaf grade is a measure of the leaf content in cotton. Recent extensive research and development work has
resulted in acceptance of instrument leaf grade. Leaf grade is now determined by high volume instrument trash
meter percent area and particle count (described above for trash). The leaf grade is calculated from these
parameters based on the Universal Upland Grade Standards and American Pima Grade Standards. Plant variety,
harvesting methods, and harvesting conditions affect leaf content. The amount of leaf remaining in the lint after
ginning depends on the amount present in the cotton before ginning, the amount of cleaning, and the type of
cleaning and drying equipment used. Even with the most careful harvesting and ginning methods, a small amount
of leaf remains in the cotton lint. From the manufacturing standpoint, leaf content is all waste, and there is a cost
factor associated with its removal. Also, small particles cannot always be successfully removed, and these
particles may detract from the quality of the finished product.
Extraneous matter is any substance in the cotton other than fiber or leaf. Examples of extraneous matter are bark,
grass, spindle twist, seedcoat fragments, dust, and oil. The classer will note, using a remark, other factors such as
the kind of extraneous matter and an indication of the amount (light or heavy). Another factor noted on the
classification record under “extraneous matter” is abnormal preparation. “Preparation,” or “prep,” describes the
degree of smoothness or roughness of the ginned cotton lint. Various methods of harvesting, handling, and
ginning cotton produce differences in roughness or smoothness of preparation that sometimes are quite apparent.
Abnormal preparation of Upland cotton has greatly decreased in recent years as a result of improved harvesting
and ginning practices, and now occurs in less than half of one percent of the crop.
Module averaging is a voluntary program offered since 1991 to Cotton Program customers at no additional
charge. It is a method to improve the reproducibility of the high volume instrument measurements of cotton
strength, length, length uniformity, and micronaire. Improved reproducibility and accuracy enhance the value of
U.S. cotton classification and allow all parties to trade U.S. cotton with greater confidence in the quality
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