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
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:
Cool White Fluorescent 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.