Sampling procedure of bales,No.of tests and critical difference % for various fiber properties
Sampling and Selection Procedure
There are three main requirements for sampling that are necessary knowledge, experience and required degree of integrity of the concerned process. Sample is the base of all procurement operations so it should be truly representative of the quality of the lot. The degree of estimated variation in cotton quality should determine the percentage of sampling. Previously, when regularity and uniformity in quality was greater, only one percent sampling was considered sufficient but when variation in our cotton increased, sampling percentage was increased to 3% by breaking the bales and 10 % by hooking the bales. Now, the variation has increased to such an extent that this percentage does not cover the variation.
The samples should be correctly drawn, marked properly and kept in safe custody so as to avoid any chance of tempering and manipulation. The moisture contents of the lots should also be checked before sampling and should be mentioned on the sample slip containing all necessary detail of the lot. The samples should be sent to the concerned classing room/ laboratory as early as possible where after due conditioning, it should be classified and evaluated to determine the important fiber properties and character of cotton manually or instrumentally but correctly. Unfortunately, untrained, poorly paid and improperly educated persons have been engaged for this very important job of sampling who are generally lured by the hospitality, some gratification known as selectory, and importance offered by the Ginners. When any representative of the buyers approaches the Ginner for purchase of lint cotton, they Ginners offers all available cotton bales of survey, sampling and selection and the good selector selects best of the cotton at normal rates. Unless the sellers have complete knowledge, he cannot get better price of his products/commodity. In other countries the Ginners / Growers get each and every loft of cotton sampled and evaluated independently.The Buyers have to accept the evaluation of the lint cotton lot and pay the price accordingly.
Different fiber properties are determined by different instruments but one compact and high-speed instrument known as High Volume Instrument (HVI) is now widely used for determining maximum fiber properties of cotton. The test values of the sample should be clearly and correctly understood and analyzed in the light of the requirement for the order of the priorities of various fiber properties. The Chief Cotton Classifier or Lab Incharge should recommend the lots considered most suitable objectively for purchase. As raw cotton has about 2/3 rd. share in the cost of yarn so it should be given due importance. Poor quality cotton will produce poor quality yarn. The services of well-qualified and experienced Cotton Classifier should be hired for selecting right type of cotton and in the view of high cost of raw material, greater emphasis required to be laid on this aspect. The weighing of cotton should carefully be done.