TYPES OF TEST

The Non technical Test FEELING TEST BURNING TESTS

The Technical Test MICROSCOPIC TEST CHEMICAL TEST

Tests for identification

Handle/Feel TestVisual ExaminationBurning testTwist on DryingFloatation TestMicroscopic analysisChemical Analysis

Requirements for tests:

Preparation of test specimenApparatus for microscopic examinationReagents used for chemical testsOther tools and equipment

THE NON-TECHNICAL TESTS

Feeling testBurning test

FEELING TEST

The feeling test requires perception if it is to be of any value.

Skilled perception is acquired only after handling many different fabrics over a period of time.

Limitations of this test become apparent when examining and comparing fabrics of different fiber content.

BURNING TEST

To recognize the composition of fabrics by the burning test ,the sample of fibre, yarn of fabric should be moved slowly towards a small flame and the reaction to heat carefully observed .One end of the sample should be put directly into flame to determine its burning rate and characteristics. The burning odour should be noted and the characteristics of the ash such as amount ,form, hardness and colour should be examined.

IDENTIFICATION OF FIBRES THROUGH BURNING TEST

CottonWhen ignited it burns with a steady flame and smells like burning leaves. The ash left is easily crumbled. Small samples of burning cotton can be blown out as you would a candle.LinenLinen takes longer to ignite. The fabric closest to the ash is very brittle. Linen is easily extinguished by blowing on it as you would a candle.

SilkIt is a protein fibre and usually burns readily, not necessarily with a steady flame, and smells like burning hair. The ash is easily crumbled. Silk samples are not as easily extinguished as cotton or linen.WoolIt is also a protein fibre but is harder to ignite than silk as the individual "hair" fibres are shorter than silk and the weave of the fabrics is generally looser than with silk. The flame is steady but more difficult to keep burning. The smell of burning wool is like burning hair.

Man Made Fibres

AcetateAcetate burns readily with a flickering flame that cannot be easily extinguished. The burning cellulose drips and leaves a hard ash. The smell is similar to burning wood chips.AcrylicAcrylics burn readily due to the fibre content and the lofty, air filled pockets. A match dropped on an acrylic blanket can ignite the fabric which will burn rapidly unless extinguished. The ash is hard. The smell is acrid or harsh.

NylonNylon melts and then burns rapidly if the flame remains on the melted fibre. If you can keep the flame on the melting nylon, it smells like burning plastic.PolyesterPolyester melts and burns at the same time, the melting, burning ash can bond quickly to any surface it drips on including skin. The smoke from polyester is black with a sweetish smell. The extinguished ash is hard.

RayonIt is a regenerated cellulose fibre which is almost pure cellulose. Rayon burns rapidly and leaves only a slight ash. The burning smell is close to burning leaves.

LIMITATION OF BURNING TEST

It is apparent that many fibers have similar burning reactions that might cause doubt and occasional confusion.

TECHNICAL TESTS

There are certain technical tests performed for identifying various fibers. These tests require high technology laboratory equipment and are much more reliable than the non technical fibre tests.

Technicals tests require high skilled personnel and technical know how of handling chemicals and their accurate analysis. These tests are very valuable for those fabrics that are a blend of different yarns and also have certain special properties including flame retardance etc.

TYPES OF TECHNICAL TEST

Microscopic testChemical test

MICROSCOPIC TEST Microscopic test is a technical test that involves identifying

the fabric with the help of a microscope with a magnification of minimum 100 power.

The test can easily distinguish between fibers. The test identifies the natural fibers more easily as compared

to man made ones. Synthetic fibers are very similar in appearance and the

increase in the number of varieties, makes it a little tough to distinguish the fibers even under a microscope.

MICROSCOPIC TEST FOR NATURAL FIBERSCOTTON: It is a single elongated cell. Under the

microscope, it resembles a collapsed, spirally twisted tube with a rough surface.

The thin cell wall of the fiber has from 200 to 400 convolutions per inch.

LINEN: Under the microscope, the hair like

flax fiber shows several sided cylindrical filaments with fine pointed ends.

The fiber somewhat resembles a straight, smooth bamboo stick with nodes

WOOL: Under the microscope , wool’s cross section shows

three layers- epidermis, cortex and the medulla.

SILK: It appears somewhat elliptical and triangular in

cross section when we see under the microscope. It is composed of fibroin, consisting of two

filaments, called brin which is held together by sericin.

MICROSCOPIC TEST FOR MANMADE FIBERS

RAYONS: Rayon fibers have a glasslike luster

under the microscope and appear to have a uniform diameter when viewed longitudinally.

ACETATE: The cross sectional view has a

bulbous or multilobal appearance with indentations.

These indentations appear as occasional markings or striations in the longitudinal view.

NYLON: The basic microscopic appearance is

generally fine , round, smooth, and translucent.

It is also produced in multilobal cross-sectional types.

POLYESTERS: Generally, polyester fibers are smooth

and straight and the cross-section is round.

This general characteristics may be altered to achieve certain characteristics, such as texture or light reflection.

ACRYLICS: The methods of manufacturing of the acrylic fibres differ, the appearances vary accordingly.

ACRILAN ACRYLIC: It has a bean-shaped cross section, its longitudinal appearance is straight and smooth.

ORLON ACRYLIC: It has a flat, nut-shaped cross section. CRESLAN ACRYLIC: It has an almost round cross section. MOD ACRYLICS: it is of two types verel modacrylic and SEF

modacrylic

SPANDEX: Spandex fibers are unique in appearance, they appear to be groups of fibers fused together.

GLASS: The fiber is smooth, round, translucent, highly lustrous, and quite flexible.

Asbestos fibre

CHEMICAL TESTS

Chemical tests are another technical means of identifying fibers. But chemical tests are not intended for the general consumers.

Different types of chemical tests are undertaken to establish the identity of the fibers used.

These tests give accurate and precise analysis. The tests are conducted in research laboratories.

TYPES OF CHEMICAL TEST

Stain Test: Also known as the Double Barrel Fibre Identification (DBFI), the test is based on the theory that each fibre has its own distinct two- colour reaction when treated with stain.A fibre will turn to a particular colour in the presence of dilute acetic acid and to some other specific colour when stained in the presence of a mild alkali.

Solvent Test: The test involves treating the fibres in certain solvents for identifying them. The technical test is becoming difficult to conduct as most of the manufactured fibres and their blends are chemically similar. There is no individual chemical or solvent test for separating or identifying the fibres in combinations.

Distinguishing animal from vegetable fibres with an acid

As strong alkali destroy animal substances, a 5% of soda lye solution in water can be used to eliminate wool and silk fibers from a sample that contains a mixture of fiber. The vegetable fibres will not be affected by this solution.

Distinguishing vegetable from animal fibres with an acid

As dilute acid destroy vegetable fibers, a 2% sulphuric acid solution can be used. A drop of solution is placed on the sample, which is then pressed with a hot iron. The spotted area will become charred if the sample is cotton linen or rayon.

DISTINGUISHING SILK FROM WOOL: The use of concentrated cold hydrochloric acid will dissolve the silk and the wool fiber swells.

DISTINGUISHING NYLON FROM OTHER FIBRES:If the fabric is thought to contain nylon, the fabric may be immersed in a boiling solution of sodium hydroxide. The nylon is insoluble in such a solution.

DISTINGUISHING POLYESTERS FROM OTHER FIBRES:Polyester is soluble in hot meta cresol; however , unlike acetate it is not soluble in acetone, and unlike nylon it is not soluble in concentrated formic acid.

DISTINGUISHING ACRYLICS FROM OTHER FIBRES:Acrylic fibers will dissolve in 70 percent solution of ammonium thio cyanate at 130 degree Celsius but the other fibers will not.

DISTINGUISHING LINEN FROM COTTONCotton and linen are immersed in a 1% solution of fuchsine in alcohol to give red rose colour. Later , they are washed and immersed into ammonia, linen retains the red coloration but cotton does not.

DISTINGUISHING GLASS FIBERS FROM OTHER FIBRES:There are two specific solvents for quick identification of glass fibers, they are hydrofluoric acid and hot phosphoric acid.

This technical fibre identification test has the following advantages and limitations

Advantages

• More reliable than the non technical tests. • Used for both man made fibres and natural fibres. • Easily conducted. Limitations • Certain manufacturing and finishing processes like mercerizing,

affects the appearance of the fibres under the microscope. • Very dark coloured fabrics cannot be identified under microscope. • Dye stuffs must be removed from fabrics.

Fiber Identification 

test

 

fiber

Soda ash

40% sol.

Caustic soda 25% sol.

Sodium hypo chloride

Hydro chloric acid

40%

Nitric acid

15%

Nitric acid

70%

Sulphuric acid

15%

Sulphuric acid

70%

Burning in Flame

Microscopic

View

Remarks

Cotton swells Swells&

Shines

Whitened Turns yellowish

Opens up

&looses strength

Dissolves slowly

Dissolves on heating

Dissolves quickly

Burns continuously leaving grey ash of burning paper smell

Longitudinal twists.

Resistance to alkalis.

jute -do- -do- -do- ---

-

--- -do -do Dissolves -do Longitudinal irregular lines

-Rough handle

Coir --- --- Color turns pale

--- --- --- Dissolves on prolonged heating

Dissolves slowly

-do-

black ash

Opaque thick serations

Brittle & resistant to chemicals

Viscose Swells Swells & slowly dissolves

Gets weakened

Turns yellow

Dissolves on heating

Dissolves Dissolves Dissolves

quickly

Burns continuously leaving grey ash of burning paper smell

Longitudinal regular lines

Soft filaments good luster

Silk Looses strength

Dissolves Dissolves slowly

--- --- Dissolves partial;ly

--- Dissolves Self extinguishing

Leaves crushable

Black beads

Densed centre line Uneven

coating

Delicate lustrous

filaments

Wool -do- -do- Dissolves --- --- Dissolves slowly

--- Dissolves slowly

Self extinguishing

Leaves crushable

Black beads

Fish

Scales

structure

Rough crimpy

fibers

Polyester

 --- --- --- --- --- Dissolves slowly on prolonged treatment

transperant hard beads.

 

Dissolves slowly

Burns& stops leaving semi

Translucent& uniform

Resistant to chemicals

Acrylic --- --- --- --- --- Looses strength

& dissolves slowly

--- Turns yellowish brown

Dissolves & Turns yellowish brown

Burns & stops

Out of flame Leaving dark hard beads

Translucent& uniform

Lofty & more voluminous

Nylon --- --- --- --- --- Looses strength

--- Dissolves slowly

Burns & stops

Out of flame Leaving dark hard beads

Translucent& uniform

Strong

More elastic

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