The procedure for identification of textile fibers in a fabric depends on the nature of the sample, the experience of the analyst, and the facilities available. Textile Fibers Identification Process is very simple. Because laws require the fiber content of apparel and furnishing textiles to be indicated on the label, the consumer may only need to look for identification labels. If a professional wishes to confirm or verify the label information, some simple solubility and burn tests may be used. These procedures differ in their effectiveness in identifying fibers. Microscopic appearance is most useful for natural fibers. Solubility tests and sophisticated spectroscopic analyses are most effective for manufactured fibers.
Textile Fibers Identification by the Visual Inspection
Visual inspection of the textile fibers for manifestation and hand is for all time the first step in fiber identification. It is no longer possible to make an identification of the fiber content by appearance and hand alone, because manufactured fibers can resemble natural fibers or other manufactured fibers. However, observation of certain characteristics is helpful. These characteristics are apparent to the unaided eye and are visual clues used to narrow the number of possibilities.
- Length of fiber. Untwist the yarn to determine fiber length. Any fiber can be made in staple length, but not all fibers can be filament. For example, cotton and wool are always staple and never filament.
- Luster or lack of luster. Manufactured fiber luster may range from harsh and shiny to dull and matte.
- Body, texture, hand. These factors indicate whether the fiber is soft to hard, rough to smooth, warm to cool, or stiff to flexible. These aspects relate to fiber size, surface contour, stiffness, and cross-sectional shape.
Textile Fibers Identification by the Burn Test
The burn test can be used to identify a fibers general chemical composition, such as cellulose, protein, mineral, or synthetic. Blends cannot be identified by the burn test. If visual inspection is used along with the burning test, fiber identification can be carried further. For example, if the sample is cellulose and also filament, it is probably rayon; but if it is staple a positive identification for a specific cellulosic fiber cannot be made.
Work in a safe, well-ventilated area or under a hood. Remove paper and other flammable materials from the area. Follow these general directions for the burn test:
- Ravel out and test several yarns from each direction of the fabric to determine if they have the same fiber. Differences in luster, twist, and color suggest that there might be more than one generic fiber in the fabric.
- Hold the yarn horizontally, as shown in. It is helpful to roll long pieces of yarn into a flat ball or clump, as shown in the figure. Use tweezers to protect your fingers. Move the yarns slowly into the edge of the flame and observe what happens. Repeat this step several times to check your results.
Textile Fibers Identification by the Microscope
Knowing the physical structure of fibers will be of use when using a microscope in fiber identification. Identification of natural fibers is best done by Microscopy. Manufactured fibers are more difficult to identify because many of them look alike, and their appearance may be changed by variations manufacturing process. Positive identification of the manufactured fibers by microscopy is not possible.
A cross section of the fiber will provide additional information. Longitudinal and cross-sectional photographic of individual fibers are included in the fiber chapters. These may be referred to when identifying unknown fibers.
The following are directions for using the microscope
- Clean the lens, slide, and cover glass.
- Place a drop of distilled water or glycerin on the slide.
- Untwist a yarn and place several fibers from the yarn on the slide. Cover with the cover glass and tap to remove air bubbles. (Make sure you are examining several individual fibers, not a yarn.)
- Place the slide on the stage of the microscope and focus with low power first. If the fibers have not been well separated, it will be difficult to focus on a single fiber. Center the fiber or fibers in the viewing field. Then move to a lens with greater magnification. As magnification increases, the size of the viewing field decreases. Thus, if fibers are not in the center of the field when a higher magnification is selected, they may disappear from the viewing field.
- If a fabric contains two or more fiber types, examine each fiber and both warp and filling yarns.