Stain test is another fiber identification process. I have already written about the solubility test which is a chemical testing method. This type of test show the natural shades of the fiber. All the fibers have not same natural color and it can find out by treated the fibers with the drop of zinc chloro-iodide reagent.
Procedure Of Stain Test To identify The Textile fibers: Here, I have described about the stain test for identiy the textile fiber. Here it is-
- At first, different natural fibers are taken for test.
- A few fibers are placed on the microscopical slide.
- A drop of zinc chloro-iodide reagent is apply on the fiber and cover with a cover slip taking care to avoid bubbles.
- Examine the fibers for staining.
- By the observation, we will find the following results-
- Hemp, Ramie and cotton stain violet.
- Flax stain brownish violet.
- Jute stain brown.
- Many other fibers stain shades of yellow brown including silk.
- Warm a few fresh fibers on a microscopical slide with a drop of acid Phlorogucinol reagent.
- Woody fibers such as unbleached jute stain deep magenta because of presence of Lignin.
So, after observing the test sample we can decide about the fiber. It is most common process for know the natural shade of the fiber. Also, we can carry out density test, drying twist test and others for identify the fibers.
Drying twist test is important test for fiber identification. Here, fiber is identify by the direction of twist. Fiber could be twisted in clockwise or anti-clockwise direction. By observing the twist direction we can identify the fiber types.
Procedure of Drying Twist Test: Here, I have given a drying twist testing procedure. Drying twist test is performed as the following way.
- At first, few parallel fibers are separate out.
- Then, fiber is making wet thoroughly by dip in the water.
- Excess water is removed with the tissue or by squeezing.
- Tap the end of the bundle to make separate fibers flare out.
- Free end is holding over a hot plate in warm to dry the fibers.
- Hold the fibers so that the free ends point is easy to observe by the observer.
- Then, note the direction of twist as the fibers dry.
- After observing the twist direction, we can give a result
- If twist direction is in a clockwise then they are Linen, Ramie, and Nettle.
- If twist direction is in anti-clockwise then it is Hemp and most of the fibers show the same twist direction.
- If twist direction is in alternating clockwise and anti-clockwise then it is Cotton fiber.
So, after observing the result we can give the identity of the fiber. Other thing is that, we can also identify the fibers by density test or solubility test.
Fiber identification is a difficult task but if we know the characteristics of that fiber then it is easy to identify the fiber. Another thing is that, if anyone want to know the name of an unknown fiber then what can we do? Simple answer is that, we can carry out various types of fiber identification test. Fiber can be identify by physical test, chemical test, burning test, density test and many more test.
Here, I like to give a chemical test procedure which is known as solubility test. It is a common testing procedure of all types of fiber. I think it will help to identify the fiber.
Procedure of Solubility Test for Fiber Identification: Followings are the solubility testing procedure:
- If we want to carry out the test then we have to maintain room temperature and place a small sample of the fiber in a watch crystal, test tube or 50 ml beaker and cover with test solvent. Here, 1 ml of solvent is used for 10 ml of fiber.
- If the test is conducted at boiling point of the solvent then first bring the solvent to a beaker for boiling on an electric hot plate in a vertical hood.
- Hot plate temperature is adjusted to maintain slow boiling and keep watch so that the solvent does not boil dry. Then the fiber sample is dropped into the boiling solvent.
- If the test is conducted at some intermediate temperature then beaker of water is heated on a hot plate and adjusts the temperature with a thermometer.
- Then, place the fiber sample in the test solvent in a test tube and immerse in the heated water bath.
- If the fiber dissolves completely then softens to a plastic mass or remains insoluble.
- Finally, compare the observation data to the standard data to identify the fiber by the solubility test.
So, that’s all about the solubility test. It is common testing process. I will discuss about the solubility testing procedure for individual fiber in my next blog.