Colour Fastness testing method

Property of a pigment or dye to retain its original hue, especially without fading, running, or changing when wetted, washed, cleaned; or stored under normal conditions when exposed to light, heat, or other influences.

 

Color fastness is usually assessed separately with respect to :

Changes in the color of the specimen being tested , that is color change

Staining of undyed material which is in contact with the specimen during the test, that is due to bleeding of color

GRAY SCALE

 

In order to give a more objective result a numerical assessment of each of these effects is made by comparing the changes with two sets of standard grey scales , one for color change and the other for staining

Arrangement of Achromatic gray chips in a scale from light to dark.

Nine pairs of non-glossy neutral grey colored chips, which illustrate the perceived color differences.

give a corresponding fastness rating of 5, 4-5, 4, 3-4, 3, 2-3, 2, 1-2, and 1)

#5 has two identical greys, and # 1 grey scale shows the greatest contrast, and # 2,3 and 4 have intermediate contrasts

Using A Gray Scale…

 

Uses a class 5-4-3-2-1 rating system.

Class 5 best, Class 1 worst.

Half Rating, such as 3-4 also used.

5-Excellent, 4-good, 3-fair, 2-poor, 1- very poor.

Specimens of a given hue are matched against these gray chips.

They equate differences in lightness with differences in color.

Grey scales for staining

 

A different set of grey scales is used for measuring staining

Fastness rating is shown by two identical white chips (that is no staining) and rating 1 shows a white and dark chips. The other numbers shows geometrical steps of contrast between white and a series of greys.

Apiece 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 given.

Grade of 5: no change in color, no staining

Grade of 1: substantially different. Heavily stained

Methodology Of Testing

 

Normally a multi-fibre strip of 6 fibre components used for staining test: Acetate, Cotton, Acrylic, Polyamide, Polyester and Wool.

Usually only one specimen of fabric used.

If material dyed or printed uniformly throughout the fabric, then specimen chosen should be representative of entire lot.

For multi –colored printed fabric, each color should be tested in order to evaluate every color.

 

CHROMATIC TRANSFERENCE SCALE

 

Is used to evaluate fabrics resistance to crocking.

Consists of six sets of color chips.

Each set is graduated from light to dark with different rating.

Lighting Used For Evaluation

 

When visually evaluating or comparing, standardized light source should be used.

COLOR MATCHING BOOTH frequently used for color checking.

COLOR MATCHING BOOTH

 

Contains 4 different standardized lights:

Daylight

Incandescent Light

Cool White Fluorescent Light

Ultraviolet Light

Each used to view specimens by pushing a switch.

Daylight used when evaluating colorfastness as color appears closer to way usually seen.

COLORFASTNESS TO WASHING

 

Ability of the fabric to with stand the effect of laundering.

Launder-o-meter is used to evaluate color fastness to washing with the help of grey scales.

The washing of fabric results in the removal of dye, therefore staining can occur, in order to determine the staining, a white multi-fiber strip is attached to the specimen being tested for CF to washing.

The staining effect on each fiber in the multi-fiber test fabric should be rated by using the grey scale for evaluating staining.