Location: Cotton Structure and Quality Research
Title: Review of Standard Test methods for Moisture in Lint Cotton Authors
Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2008
Publication Date: April 14, 2008
Citation: Montalvo Jr, J.G., Von Hoven, T.M. 2008. Review of Standard Test methods for Moisture in Lint Cotton. Journal of Cotton Science. 12:33-47. Interpretive Summary: Moisture in cotton is important because the fiber properties are strongly dependent on the actual moisture content. The standard test methods for moisture in lint cotton are almost all based on oven drying. Loss in weight is taken as the measure of moisture. The U.S. cotton industry questions the reliability of the oven drying test and has requested that this laboratory develop improved standard test methods. As a first step, the approach taken is to review the standard test methods and compare the available accuracy and precision information. No quantitative data is presented in the methods regarding accuracy; between-laboratories precision is generally poor or lacking. The practical implication of these findings is that it confirms the need by the industry for improved standard test methods for moisture in cotton. Advances in this area of work will lead to more accurate indirect methods for moisture in cotton, which must be traceable to an acceptable standard method.
Technical Abstract: Almost all of the standard test methods for moisture in lint cotton utilize the oven-drying technique. The loss in weight is taken as the amount of water and is expressed as a percentage of the mass of either the moist or dried material. There is a need to review the standard methods and compare terminology, procedures, the quantities that are calculated and measured and the known biases, and available accuracy and precision data. This review covers the standard test methods – voluntary, national and international – for moisture in lint cotton. Included are the standards in eleven countries that represent all six continents. Five of the countries (Australia, Brazil, India, S. Africa and the USA) do not have national standards and rely on voluntary standards, such as ASTM. By contrast, China and Germany have national standards. The national standards of Egypt, England, France and Italy have been superseded by the global ISO standard. Examples of the moisture terminology presented in this review includes: oven dry, bone dry, moisture equilibrium and moisture free. Procedural examples demonstrate wide ranges in the oven method specifications: sample analyzed, 1 to > 50 g; conditioning prior to drying, from none to optional to yes; standard testing environment (70o F and 65 % RH), from none to optional to yes; and oven temperature, generally 105o C to 110o C. To help understand the various moisture quantities that are calculated in the methods and provide for direct comparability, simple formulas are presented in terms of the quantities measured and the known biases. In the reviewed standards, these biases are assumed equal to zero, ignored or the standard method eliminates a specific bias. In terms of round trials, there is no quantitative accuracy information; however, the biases are readily admitted in the standards. Between-laboratories precision is generally poor or is lacking.