
Colour fastness is a term used in the
dyeing of textile materials, meaning resistance of the material's colour to
fading or running. The term is usually used in the context of clothes. The
first known use of the word colorfast was in 1916. In general, clothing should
be tested for colourfastness before using bleach or other cleaning products.
Color Fastness:
Color fastness is one of the important factors
in case of buyers demand. The outstandingly important property of a dyed
material is the fastness of the shade of color. Color fastness refers to the
resistance of color to fade or bleed of a dyed or printed textile materials to
various types of influences e.g. water, light, rubbing, washing, perspiration
etc. to which they are normally exposed in textile manufacturing and in daily
use. We have written a lot of articles on color fastness.
General Principle:
A specimen of the textile to be
tested, with the adjacent fabric attached is subjected to washing under
specified conditions. The extent of any change in color and that of the
staining of the adjacent fabric are assessed and the rating is expressed in
fastness numbers.
There are two types of adjacent fabrics; (1)
single fibre fabric and multiple fibre fabric. In the case of multi-fibre fabric only one specimen is required
and in the of single fiber fabric two adjacent fabric are required.
Standards of Color Fastness:
1. AATCC (American Association of Textile
Chemists and Colorists) technical manual:
Describes 66 numbers of different color fastness
tests.
2. SDC (Society of Dyers and Colorists):
In 1927, SDC (Europe) made fastness test
committee.
3. ISO(International Organization for
Standardization):
In 1947, ISO made color sub committee. ISO also
grades the fastness:
For light fastness: 1~8
For other fastness: 1~5
Factors Affecting the Color Fastness
Properties:
1.
The
chemical nature of the fiber. For example, cellulosic fibers dyed with reactive
or vat dyes will show good fastness properties. Protein fibers dyed with acid
mordant and reactive dyes will achieve good fastness properties and so on. That
is to say compatibility of dye with the fiber is very important.
2.
The
molecular structure (e.g.) of a dye molecule: If the dye molecule is larger in
size, it will be tightly entrapped inside the inter-polymer chain space of a
fiber. Thus the fastness will be better.
3.
The
manner in which the dye is bonded to the fiber or the physical form present.
4.
The
amount of dye present in the fiber i.e. depth of shade. A deep shade will be
less fast than a pale or light shade.
5.
The
presence of other chemicals in the material.
6.
The
actual conditions prevailing during exposure.
If the color removes itself from the
garment onto the cloth, you should not use the cleaning product on the
clothing. Important color fastness tests are given below:
1.
Color
Fastness to Washing
2.
Color
Fastness to light
3.
Color
Fastness to perspiration
4.
Color
Fastness to Water
5.
Color
Fastness to Rubbing
6.
Color
Fastness to Crocking
Color Fastness to Washing
In the test, change in color of the textile and also
staining of color on the adjacent fabric are assessed. A 10 x 4 cm swatch of
the coloured fabric is taken and is sandwitched between two adjacent fabrics
and stitched, the sample and the adjacent fabric are washed together. Five
different types of washing are specified as different washing methods.
Fastness
to Wash | ||||||
Sr.No | Method | Washing severity | Soap+Soda in grams/liter | Time in minutes | Temperature | Steel balls |
1 | IS:687:79 | Very mild like hand wash | 5 | 30 | 40+/- 2 | Nil |
2 | IS:3361:79 | 5 times severe than method 1 | 5 | 45 | 50+/- 2 | Nil |
3 | IS:764:79 | Mild washing | 5 + 2 | 30 | 60+/-2 | Nil |
4 | IS:765:79 | Severe washing | 5 + 2 | 30 | 95+/-2 | 10 |
5 | IS:3417:79 | Severe washing | 5 + 2 | 4 hrs | 95+/-2 | 10 |
The solution for washing should be
prepared to the required temperature of washing. The liquor material ratio is
50:1 . After soaping treatment, remove the speciment, rinse twice in cold water
and then in running cold water under a tap. Squeeze it and air dry at a
temperture not exceeding 60°C. The change in color and staining is evaluated
with the help of grey scales.
Color Fastness to light
The purpose of Color fastness to
light test is to determine how much the color will fade when exposed to a known
light source. It is an off line quality assurance system. Generally man wears
the fabric and goes outside of the home for doing their job. In day; sun light
fall on the fabric surface. So it needs to know how much protection ability
have a fabric to sun light. It is determined by an experiment called color
fastness to light. To measure the color fastness a blue scale is used. After
completing the test, sample is compared with the blue scale.
Principle of Color Fastness to Light:
This test measures the resistance to
fading of dyed textile when exposed to day light. The test sample is exposed to
light for a certain time which is about 24 hours to 72 hours or by
customer/buyer demand and compare the change with original unexposed sample the
changes are assessed by Blue Scales.
Light Fastness Grades:
Grade | Degree of Fading | Light
Fastness Type |
8 | No
fading | Outstanding |
7 | Very
slight fading | Excellent |
6 | Slight
fading | Very
good |
5 | Moderate
fading | Good |
4 | Appreciable
fading | Moderate |
3 | Significant
fading | Fair |
2 | Extensive
fading | Poor |
1 | Very
extensive fading | Very
poor |
Color Fastness to Perspiration:
The garments a\which come into contact with the
body where perspiration is heavy may suffer serious local discoloration. This
test is intended to determine the resistance of color of dyed textile to the
action of acidic and alkaline perspiration. Before knowing about the Color
Fastness to perspiration you must have to know about Color Fastness to Wash and
Color Fastness to Rubbing.
Color Fastness to Water
Color fastness to water is designed to measure
the resistance to water of dyed, printed, or otherwise colored textile yarns
and fabrics.The test method by which this test is carried out is AATCC 107-1991
or ISO 105 E01. This method is to assess the degree of cross staining which may
occur when garments are left in contact when damp. The test measures the
resistance to water of any colored textiles.
Color Fastness to Rubbing
This test is designed to determine the degree of
color which may be transferred from the surface of a colored fabric to a
specify test cloth for rubbing (which could be dry and Wet).
There are two test methods for rubbing
fastness.
1.ISO-105-X12
2.AATCC-08
In ISO-105-X12 the wet pickup of the rubbing
cloth is 100% .While in AATCC-08 the wet Pickup of the rubbing cloth is 65%.We
check rubbing by Dry and Wet methods. In wet rubbing we wet the rubbing cloth
according to test method and give rating by comparing the Staining with the
gray scale.
Similarly for dry rubbing we check the rubbing
with dry rubbing cloth and compare the staining With gray scale for
ratings.Color Fastness to rubbing is a main test which is always required for
every colored fabric either it is Printed or dyed.
If the color fastness to rubbing is good then
its other properties like Washing fastness and durability etc improves
automatically because the rubbing is a method to check the fixation of the
color on the fabric. So if the fixation is good its washing properties will be
good.
Rubbing Fastness depends on:
Nature of the Color
Depth of the Shade
Construction of the FabricNature of the color
Each color either it is pigment ,Reactive ,Disperse or direct has its own
fastness properties to rubbing. There are some colors like black, Red ,Burgundy
,Navy blue which have poor Color fastness properties because of their chemical
structure.
Like Black color is a carbon base color and the
particle size of carbon is large than the other colors that's why its rubbing
properties are poor. Similarly red and blue are in the same case. So to improve
the color fastness we add more binder to improve the fastness properties of
these colors. It doesn't mean that we can not achieve the best results with these
colors. The required results can achieve but production cost will be increase.
On the other hand the construction of the fabric also effects the fastness
properties.
If the rubbing fastness on 100.80/40.40 is 3 on
the gray scale it will be 2-3 on 52.52/22.22 with the same printing parameters.
So always keep in mind these effects during finalize the required parameters
with your customer.
Color Fastness for Crocking
Crocking is simply the transfer of color from a
fabric onto another white test fabric. The more color is transferred, the more
the fabric "crocks". Crocking determines the amount of color
transferred from the surface of colored textile material to other surfaces by
rubbing.