The Cotton Testing Guideline
Cotton Fiber Testing for Efficiency and Profitability
The Cotton Testing Guideline, first published in 2012 and revised in 2018 jointly by the International Textile Manufacturers Federation and the Task Force on Commercial Standardization of Instrument Testing of Cotton, answers many questions about how to test cotton using high-volume testing instruments. This companion publication, the Interpretation Guideline, explains how to use and interpret instrument test results.
The purpose of the Interpretation Guideline is to encourage understanding of instrument testing, thereby leading to greater efficiency in all areas of the cotton value chain, with a resulting improvement in efficiency and profitability.
This Executive Summary provides a short overview of the Interpretation Guideline, but detailed explanations and useful insights can be found in the full text. There are separate chapters on each measured cotton fiber property and subchapters for producers, ginners, merchants and spinners.
Cotton is a natural product, and there is naturally variability in fiber properties within every sample, between samples of the same bale and between bales. The variation in the measurement of each fiber property is quantified in Chapter 4, and information on the use of instrument testing data to manage cotton inventories and processing within the limits imposed by the natural variation in measurement results is provided. The distribution of results provided by instrument testing can be used to advantage because it represents an accurate description of the characteristics of bales in sales lots and laydowns.
- The micronaire of a given sample of cotton is affected by both genetics and environmental factors during the growing season.
- When comparing samples of cotton of the same growth, differences in micronaire reflect differences in maturity. However, when comparing samples of different growths but similar levels of maturity, differences in micronaire reflect differences in fineness.
- For producers, micronaire can assist in the comparison of seed varieties.
- For trading, it is used as an easy and reliable guide regarding the combination of fineness and maturity.
- For spinners, fineness is crucial in predicting the spinnability of cotton and the fineness, evenness and strength of the yarn that might be produced from it.
- Micronaire is important to predict the dyeability, fiber neps and the appearance of yarn and fabric.
This is usually understood to mean the Upper Half Mean Length (UHML). Uniformity Index (UI) and Short Fiber Index (SFI) are additional measures related to the fiber length distribution.
- Length is affected by genetics, environment during the growing season, and ginning
- Instrument measurements of UHML are usually similar to the results assigned by classers pulling staple. Classers assign staple lengths in 32nds of an inch, whereas instrument results are given in hundredths of an inch or millimetres and are more easily used in calculations of the mean or standard deviation over a number of samples.
- Length is one of the most important parameters used in all segments of the cotton value chain.
- Length is the most important property in the production of ring spun yarn.
- Length affects the spinnability of cotton and influences the number of twists per inch of yarn required to achieve a given level of strength. Length is the most important property in setting drafting parameters within a textile mill.
- Length distribution strongly influences nearly all yarn quality parameters. UHML affects yarn strength. Length uniformity influences evenness, and SFI affects hairiness.
- Strength is a result of seed variety and growing conditions.
- Excessive drying and the use of lint cleaners during ginning will reduce strength and lead to increased fiber breakage.
- Strength is the most important property for Open End (Rotor) and Air-Jet spinning.
- Fiber strength and length influence yarn strength, which is crucial in weaving yarns.
Classers assign a single color grade to a sample. Instrument results are a combination of reflectance (Rd) and yellowness (+b). Color grades and instrument results can be mapped one to the other using a Nickerson-Hunter diagram.
- Changes in color indicate the history of a bale of cotton. Cotton can change in color from white to grey or yellow, depending on how it was grown and harvested, whether it rained during harvest, how much moisture was in the seed cotton and how long it was stored prior to ginning. Grey or yellow cotton will generally be weaker than white cotton.
- In processing, color is important for dyeing and the homogeneity of dyeing.
Trash consist mainly of leaves from the cotton plant.
- Trash is influenced by harvesting method: hand, spindle or stripper.
- For a given harvest method, ginning will have the dominant impact on trash content.
- Trash can be partially removed at the gin using lint cleaners or in the carding and combing processes at the textile mill prior to the cotton reaching the spinning frames.
- In trading, trash represents non-lint content of bales and thus has a negative impact on prices
- Trash has a negative impact on textile processing.
- Nep formation (fiber entanglement) is influenced by fiber maturity and the intensity with which cotton is processed. Slow and careful processing from ginning through spinning reduces nep formation.
- Neps influence the yarn appearance negatively.
- Stickiness caused by white fly or aphid infestation interferes with the spinning process, particularly in drafting. Very sticky cotton can bring a textile mill to a halt.
- Spinning Consistency Index is a summary parameter that is determined by the results of micronaire, strength, length, length uniformity and color in high volume testing instruments.
- Fiber moisture affects processing. Dry fiber is prone to higher rates of breakage.
A summary of the influences of each fiber parameter is given in the following table: