FASH 15 textiles

fiber identification

fiber identification

the procedure for identifying fibers in a fabric depends on:•the nature of the sample•the experience of the analyst•the facilities available

microscopic appearance is most useful for natural fibers

solubility tests & sophisticated spectroscopic analyses are most effective for manufactured fibers

fiber identification: visual inspection

visual inspection of a textile for appearance and hand is always the first step in fiber identification

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, 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 and relate to fiber size, surface contour, stiffness and cross-sectional shape.

fiber identification: burn test

the burn test can be used to identify a fiber’s general chemical composition—cellulose, protein, mineral, or synthetic (blends cannot be identified)

EXAMPLE: if sample is cellulose & filament, probably rayon

safety precautions:•work in well-ventilated area or under a hood•remove paper and other flammable materials from area•check apparel and hair are safely out of the way

fiber identification: burn test

follow these general directions:•ravel out and test several yarns from each direction of the fabric to determine if they are the same fiber type—differences in luster, twist, and color suggest that there might be more than one generic fiber in the fabric

•hold the yarn horizontally—it is helpful to roll long pieces of yarn into a flat ball or clump•use tweezers to protect your fingers•move yarns slowly into the edge of the flame and observe what happens•repeat this step several times to check your results

fiber identification: microscopy

knowing the physical structure of fibers will be of use when using a microscope in fiber identification— photomicrographs of fibers included in Ch. 4-9

for best accuracy, examination of both the lengthwise appearance (longitudinal) and crosswise appearance (cross-section) of an unknown fiber is best

positive identification of manufactured fibers by microscopy is not possible

fiber identification: microscopy

directions for using the microscope:•clean the microscope lens, glass 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•place the slide on the stage of the microscope•focus with low power first—center fiber(s) in the viewing field then move to a lens with greater magnification (as magnification increases, viewing field decreases)•if fabric contains 2 or more fiber types, examine both warp and filling yarns

fiber identification: solubility tests

solubility tests are used to identify manufactured fibers by generic class and to confirm identification of natural fibers

fiber identification: solubility tests

directions for solubility tests: •place the specimen in the liquid in the order listed—following this order will help in identifying specific fiber•stir the specimen for 5 minutes and note the effect•fiber, yarns, or small pieces of fabric may be used•remember that the liquids are hazardous—handle them with care!•use chemical laboratory exhaust hoods, gloves, aprons & goggles

fiber identificationLAB #1—burn tests

…please read and follow all the directions on your lab sheets VERY CAREFULLY…please listen to the instructor before you begin anything…if you have questions, please ask