Fiber Maturity tests

Methods of determination of maturity:

Several methods are available to determine the maturity of cotton. These can be grouped as below:

1. Direct method - caustic soda swelling method
2. Indirect method.
   1. Differential dyeing method
   2. Causticaire method
   3. Polarized light method.

 1) Direct method- Caustic soda swelling method

                                   It is the most commonly used method A thin tuft of fibers is drawn by means of tweezers from a silver held in a comb sorter. The tuft is laid on a microscope slide., the fibers parallel and separated and a cover slip is put over the middle. Likewise four to eight slides are prepared. There are two steps involved in this method.

         1. Treatment with 18% caustic soda.

         2. Examination under a microscope to count the mature, half mature and immature fibers.

                                     The fibers on the microscope slide are then irrigated with a small amount of 18% caustic soda solution, which has the effect of swelling them. The slide is then placed on the stage of a microscope and examined. The presence or absence of the convolution is observed and the fibers are classified into three groups.

            1. Mature or normal fibers.

            2. Half mature or thin walled fibers.

            3. Immature or dead fibers.

                   The presence of caustic soda changes the appearance of both mature and immature fibers by swelling. Mature fibers with a well developed cell wall and pronounced convolutions in the raw state become rod like swelling. These rod like fibers are classified as normal or mature fibers.

                   In the case, the lumen is practically absent. Dead or immature fiber appear ribbon like even after swelling. In dead fibers, the wall thickness is less than 1/5th of the ribbon width. Thin walled or half mature fibers are those lying between the other two classes. 

                     The fibers are classed as above  based on the ratio of lumen width (L) to wall thickness (W) as indicated below:

             Class                                                Ratio of lumen width to wall thickness (  L / W )

            Mature                                                    Less than 1

            Half mature                                             1 - 2 

            Immature                                               Greater than 2

            All the slides are examined as above and the percentage of mature ( N ) half mature  ( H )

and the immature ( I ) fibers are calculated. Then the maturity of the cotton fiber is expressed by any one of the following terms:

          1. Percentage of Mature fibers , N

          2. Maturity ratio , M

          3. Maturity co-efficient, Mc