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Presentation by:-Rashmi.R

1st MHSc (TAD )

Assessment of Color Fastness in Textiles

Fastness is the resistance of a textile material to specific chemical agencies. Poor color fastness in textile products is a major source of customer complaint. The fastness of a color can vary with the type of dye, the particular shade used, the depth of shade and how well the dyeing process has been carried out. Dyes can also behave differently when in contact with different agents, for instance dyes which may be fast to dry-cleaning may not be fast to washing in water. It is therefore important to test any dyed or printed product for the fastness of the colors that have been used in its decoration. 

Fastness

Colorfastness

A distinction should be made between dyeing(internal pigmentation) and

printing(external pigmentation). The buyer has a right to expect dyed fabrics to

withstand the deterioration elements or influences to which the finished cloth will be

subjected such as:-

Sunlight Perspiration Washing Friction

Evaluation of fastness properties of a dye is done by measuri

ng:-

Washing- Wash Wheel

Light- Xenoster

Rubbing -Crock meter

Perspiration- Perspiromet

er

Evaluation of Fastness Properties

Fastness To Sunlight

XENOMETER

XENOSTER •This is used to test the light fastness of the dyed fabric. •color fastness to light, By Xenotester

Commercial testing agencies frequently use standard tests to light fastness specially designed powerful carbon arc lamp has the same effect as that of sunlight. Samples to be tested revolved around this lamp for definite period of exposure.

After processing, comparison in the change in color of the specimen with the changes that have  occurred in the  standard pattern under suitable illumination is carried  out to determine the fastness of  light.

Function of Xenometer

The best way in which to determine fastness to launder a fabric.

A10 x 4 cm swatch of the dyed fabric is taken and is sandwiched between two adjacent fabrics and  stitched.

 The sample and the adjacent fabric were washed together. Five different types of washing are  specified as different washing methods.

•The solution should be preheated to the required temperature of washing.  After soaping treatment, the specimen is removed, rinse twice in cold water , Squeezed and dried in air at a temperature no

t exceeding 60°C. the value is evaluated  with the help of grey scales.

Fastness to Laundering

Features of Washing Fastness Tester:-

•It is fabricated out of quality stainless steel. •Possess electric heater to heat water in water 

bath. •The microprocessor based programmer is pro

vided for temperature control. Buzzer to indicate the completion of the proces

s cycle or step.

WASH FASTNESS

WASH FASTNESS TESTER

FASTNESS TO RUBBING

The test is quite:-Sensitive and for getting consistent result, it is necessary to use

Standard crock meter Cloth, Maintain uniform pressure for applying

 rubbing strokes and number of strokes. 

Crock meter is used for testing the transference of color from the surface of one material to 

another by either wet or dry rubbing.

In this there are two types of Crocking:-

Dry crocking:-

A 2” square of colored fabric

rubbed against a piece of white sheeting. Any

discoloration of the fabric itself, the color is not

fast to dry crocking.

Wet crocking:-

A piece of white sheeting

should be dampened and rubbing against

the piece of untested

colored fabric. Any

discoloration of the white cloth

should be noted. If this occurs, the

color is not fast to wet crocking.

COLOUR FASTNESS TO RUBBING

Fastness to perspiration

•The fastness of colored fabric with reference to alkaline and acidic perspiration was evaluated.  For the alkaline (pH‐8) and acidic (pH‐5.5) liquors were prepared and the composite specimens  were dipped in acidic and alkaline solution separately for 30 minutes. Good and uniform penetration of the solution was ensured. The liquor was poured off and the excess water and air  bubbles, if any were removed by passing the specimens in between two glass rods. Composite  specimens were then placed between glass/acrylic plates with a pressure of 12 kpa per spirometer.  The perspirometer,was kept for four hours at a temperature of 37 (±2

0C).  Afterwards, the fabrics were removed, separated and dried in air below 60°C. The values were  rated as per the grey scale. The details of the values assigned for these properties are:

•5  =Negligible (Excellent) •4  =Slightly changed (Good) •3  =Noticeable changed (Fairly good) •2  =Considerably changed (Fair) •1  =Much changed (Poor)

 The values were  rated as per the grey scale. The details of the value

s assigned for these properties are:-

Perspirometer

There are two types of pressing:-

Hot pressing Wet pressing

Color fastness to Pressing

Hot pressing

Soak the test specimen and a piece of cotton

adjacent fabric in distilled water and squeeze it to maintain 100% pick up.

Place the soaked cotton fabric on top of the dry test specimen and repeat

Wet pressing

COLOUR FASTNESS

ASSESSMENT BY USE OF GREY SCALE

A different set of grey scales is used for measuring staining. Fastness rating -5 is shown by two identical white samples and rating 1 shows a white and a grey sample.

The other numbers show geometrical steps of contrast between white and a series of greys. A piece of untreated, unstained, undyed cloth is compared with the treated sample that has been in contact with the test specimen during the staining test and a numerical assessment of staining is given.

A rating of 5 means that there is no difference between the treated and untreated material. If the result is in between any two of the contrasts on the scale, a rating of, for example, 3-4 is given. Sets of grey scales, examples of which are shown in Fig: can be supplied by the British Standards Institution. 

References:-Wingate Isabel Barnum and Mohler, Textile Fabrics and their selection Book,1984 , New Jersey, page (187-192).

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