Determination of Fiber Maturity on Direct Method: Caustic Soda Swelling Method/ Lab Report

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Name of the Experiment:

Study on measure of fiber maturity on direct method: Caustic soda swelling method.


An important characteristic of cotton is fiber maturity, which indicates how much the fiber has developed. It is important to note that cotton fiber maturity varies not only between fibers in different samples, but also between fibers in the same seed. An unripen cotton boll consists of both mature and immature fibers. Cotton fibers are composed of a cuticle, a primary layer, and a secondary layer of cellulose surrounding the central canal. In the case of mature fiber, the secondary wall thickening is very high and in some cases, the lumen is not visible. The secondary wall thickening of immature fibers is practically absent as a result of physiological factors, leaving a wide lumen. Thus, excessive immature fibers in a sample would indicate some kind of plant growth defect, either varietal or environmental. An excessive percentage of immature fiber in a sample is undesirable as it causes waste, losses in processing, lowering the yarn appearance grade due to needle formation and uneven dyeing. Several methods are available for determining the maturity of cotton. These can be grouped as follows:

  1. Direct method-Caustic soda swelling method.
  2. Indirect method.
    • Differential dyeing method.
    • Causticaire method.
    • Polarized light method.

In this experiment, we learn about direct method-caustic soda swelling method.


  1. To know about fiber maturity.
  2. come to learn different methods of determination of fiber maturity.
  3. To know how to determine fiber maturity by using caustic soda swelling method.


  1. Tweezers.
  2. Comb sorter.
  3. Microscope.
  4. Slide.

Sample preparation:

It is the most commonly used method. The tweezers are used to draw a thin tuft of fibers from a comb sorter. After placing the fibers on a microscope slide, ensure they are parallel and separate each other. Next, a cover slip is placed on top of the tuft. In the same manner, eight slides are pre-paned.

Working procedure:

There are two step involved in this method:

  1.  Treatment with 18% caustic soda.
  2. Examination under a microscope.

1. Treatment with 18% caustic soda: at first, 18% caustic soda solution is prepared. Then the fibers on the microscopic slides are irrigated with a small amount of 18% caustic soda solution. 18% caustic soda solution has the effect of swelling.

2. Examination under microscope: then the slide is placed on the stage of a microscope and examined. The presence or absence of convolution is observed and the fibers are categorized into three groups.

Figure 01: Fiber under microscope
  1. Mature or normal fiber: Matured fibers with a well-developed cell wall appear rod-like after swelling and the longitudinal section of matured fibers shows no continuous liner.
  2. Half mature or thin walled fiber: It is hard to determine which of these are normal. Some have a rod-like shape, but not all of them have a continuous lumen. The fibers in this group are on the other end of the spectrum and approach the dead class, but their wall thickness is greater than a fifth of the ribbon width.
  3. Immature or Dead fiber: This is when the wall thickness is one fifth or less of the maximum ribbon width. Dead fibers can present as float ribbons with no second flat fiber wall, or as highly convoluted forms with a greater wall thickness.

Calculation of Fiber Maturity:

All the slides are examined and calculated the percentage of mature (N), half mature (H), and Immature (I) fiber. Then the maturity of the cotton fiber can be expressed by any one of the following terms.

  1. Percentage of mature fiber (N).
  2. Maturity ratio (M).
  3. Maturity co-efficient (Mc).

1. Percentage of mature Fiber (N) :

Percentage of mature fiber can be calculated by knowing the total number of fibers examined and the number of mature fiber. Following formula can be used. In our experiment, we found number of mature fiber 67 and total number of fiber examined 100.

2. Maturity Ratio (M):

maturity ratio can be calculated using the following equation.

The theoretical value of M will vary from 0.2 for all dead fibers to 1.2 for all matures fiber.

3. Maturity Co-efficient:

the fiber maturity count is denoted by the percentages of the mature, half mature and immature fiber. It can be calculated by using the following formula,

Based on the maturity co-efficient, the cottons are classed into following groups:

Maturity co-efficientRating
Below 0.06Very immature
0.60 to 0.70Immature
0.71 to 0.80Average maturity
0.81 to 0.85Good maturity.


Our maturity co efficient is 0.85. According to the above table, our fiber maturity is good.


In this experiment, we learned a lot about the maturity of fiber, as well as the method of determining cotton fiber maturity with caustic soda. We also learned to calculate the percentage of mature fiber, maturity ratio, and maturity coefficient. This experiment will help us in our career life. I would like to thank our teacher for helping us.

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  2. Working Principle of Beesley Balance.
  3. Working Principle of Quadrant Balance.
  4. Fiber fineness test sheffield micronaire: Air flow method

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